Circuit device and oscillator

Abstract

To provide a circuit arrangement in which an external device can highly accurately calculate a duty ratio of a clock signal output from an external connection terminal.SOLUTION: A circuit arrangement comprises: an oscillation circuit that generates an oscillation signal; a first buffer circuit that outputs a first clock signal based on the oscillation signal; a second buffer circuit that outputs a second clock signal based on the first clock signal; a first terminal that allows the first buffer circuit to electrically connect with a first node that outputs the first clock signal; and a second terminal that allows the second buffer circuit to electrically connect with a second node that outputs the second clock signal. The rise time of the first clock signal is shorter than that of the second clock signal.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a circuit device and an oscillator. [Background technology]

[0002] Patent Document 1 describes an oscillation circuit in which an inversion circuit causes a crystal oscillator to vibrate, the output signal of the inversion circuit is input to multiple inversion buffers, and a clock signal is output from the final-stage inversion buffer, while a low-pass filter is used to average the duty ratio of the clock signal, and the analog value is used for feedback control to maintain the duty ratio of the clock signal at 50%. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-073246 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, as in the oscillator circuit described in Patent Document 1, the clock signal output from the final stage buffer is output from the external connection terminal to the outside, so that if the load connected to the external connection terminal is large, the rise time and fall time of the clock signal may be long. In addition, the clock signal output from the external connection terminal may have a waveform with a long rise time and fall time intentionally in order to reduce EMI noise. In this way, a clock signal with a long rise time and fall time has a distorted waveform compared to a rectangular waveform, so the correlation between the DC voltage smoothed by a low-pass filter and the duty ratio becomes complicated. Therefore, it is difficult to calculate the duty ratio of the clock signal output from the external connection terminal with high accuracy based on the DC voltage smoothed from the clock signal. [Means for solving the problem]

[0005] One aspect of the circuit device according to the present invention is an oscillator circuit for generating an oscillation signal; a first buffer circuit that outputs a first clock signal based on the oscillation signal; a second buffer circuit that outputs a second clock signal based on the first clock signal; a first terminal electrically connectable to a first node at which the first buffer circuit outputs the first clock signal; the second buffer circuit includes a second terminal electrically connected to a second node at which the second buffer circuit outputs the second clock signal; The rise time of the first clock signal is shorter than the rise time of the second clock signal.

[0006] One aspect of the oscillator according to the present invention is One aspect of the circuit device; and a vibrator. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a perspective view of the oscillator according to the embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the oscillator according to the embodiment. [Diagram 3] FIG. 2 is a functional block diagram of an oscillator according to the first embodiment. [Figure 4] FIG. 2 is a diagram showing a configuration example of an oscillator circuit. [Diagram 5] FIG. 4 is a diagram showing an example of the voltage waveforms of clock signals CKO and CK4. [Figure 6] 4 is a diagram showing an example of the relationship between the duty ratio of a clock signal CKO and a DC bias. [Figure 7] FIG. 13 is a diagram showing an example of the relationship between the duty ratio of a clock signal CK4 and a DC bias. [Figure 8] 3 is a diagram showing details of each circuit on a signal propagation path from an XI terminal to a T3 terminal or a T4 terminal in the first embodiment. FIG. [Figure 9]FIG. 4 is a flowchart showing an example of a procedure of a method for testing the duty ratio of a clock signal CKO output from the oscillator according to the first embodiment. [Figure 10] 6A and 6B are diagrams showing examples of voltage waveforms of control signals of terminals and switches when inspecting a duty ratio. [Figure 11] FIG. 11 is a functional block diagram of an oscillator according to a second embodiment. [Figure 12] 13 is a diagram showing details of each circuit on a signal propagation path from an XI terminal to a T3 terminal or a T5 terminal in the second embodiment. FIG. [Figure 13] FIG. 11 is a flowchart showing an example of a procedure of a method for testing the duty ratio of a clock signal CKO output from an oscillator according to the second embodiment. [Figure 14] FIG. 11 is a functional block diagram of an oscillator according to a third embodiment. [Figure 15] FIG. 13 is a diagram showing details of each circuit on a signal propagation path from an XI terminal to a T3 terminal or a T4 terminal in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0009] 1. First embodiment 1-1. Oscillator configuration 1 and 2 are diagrams showing an example of the structure of an oscillator 1 according to the present embodiment, Fig. 1 is a perspective view of the oscillator 1, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1.

[0010] As shown in FIG. 1 and FIG. 2, the oscillator 1 includes a circuit device 2, a vibrator 3, a package 4, a lid 5, and a plurality of external terminals 6. In this embodiment, the vibrator 3 is a quartz crystal vibrator using quartz crystal as a substrate material, such as an AT-cut quartz crystal vibrator or a tuning fork-type quartz crystal vibrator. The vibrator 3 may be a SAW (Surface Acoustic Wave) resonator or a MEMS (Micro Electro Mechanical Systems) vibrator. In addition to quartz crystal, the substrate material of the vibrator 3 may be a piezoelectric material such as a piezoelectric single crystal such as lithium tantalate or lithium niobate, a piezoelectric ceramic such as lead zirconate titanate, or a silicon semiconductor material. The vibrator 3 may be excited by a piezoelectric effect or by electrostatic driving using Coulomb force. In this embodiment, the circuit device 2 is realized by a one-chip integrated circuit (IC: Integrated Circuit). However, the circuit device 2 may be at least partially composed of discrete components.

[0011] The package 4 accommodates the circuit device 2 and the vibrator 3 in the same space. Specifically, the package 4 is provided with a recess, and the recess is covered with a lid 5 to form an accommodation chamber 7. Inside the package 4 or on the surface of the recess, wiring (not shown) is provided for electrically connecting two terminals of the circuit device 2, specifically, an XI terminal and an XO terminal in FIG. 3 described later, to two excitation electrodes 3a, 3b of the vibrator 3. Also, inside the package 4 or on the surface of the recess, wiring (not shown) is provided for electrically connecting each terminal of the circuit device 2 to each external terminal 6 provided on the bottom surface of the package 4. The package 4 is not limited to a configuration in which the circuit device 2 and the vibrator 3 are accommodated in the same space. For example, the package 4 may be a so-called H-shaped package in which the circuit device 2 is mounted on one side of a substrate of the package and the vibrator 3 is mounted on the other side.

[0012] The oscillator 3 has metallic excitation electrodes 3a, 3b on its front and back surfaces, respectively, and oscillates at a desired frequency according to the shape and mass of the oscillator 3 including the excitation electrodes 3a, 3b.

[0013] 3 is a functional block diagram of the oscillator 1 of the first embodiment. As shown in FIG. 3, the oscillator 1 of the present embodiment includes a circuit device 2 and a resonator 3. The circuit device 2 has a VDD terminal, a VSS terminal, an OUT terminal, a VC terminal, an XI terminal, and an XO terminal as external connection terminals. The VDD terminal, the VSS terminal, the OUT terminal, and the VC terminal are electrically connected to the T1 terminal, the T2 terminal, the T3 terminal, and the T4 terminal, which are the multiple external terminals 6 of the oscillator 1 shown in FIG. 2, respectively. The XI terminal is electrically connected to one end of the resonator 3, and the XO terminal is electrically connected to the other end of the resonator 3.

[0014] In this embodiment, the circuit device 2 includes an oscillator circuit 10, an output circuit 20, a temperature sensor 30, a temperature compensation circuit 32, a frequency control circuit 34, a logic circuit 36, a power supply circuit 40, a memory circuit 50, an RC filter 60, and switch circuits 70, 80, and 90. Note that the circuit device 2 may be configured such that some of these elements are omitted or modified, or other elements are added.

[0015] The power supply circuit 40 generates various constant voltages based on a power supply voltage supplied from the outside via the T1 terminal and the VDD terminal, and supplies the constant voltages to each circuit. For example, the power supply circuit 40 may include a plurality of regulators that each generate a constant voltage based on the output voltage of a bandgap reference circuit.

[0016] The oscillator circuit 10 is electrically connected to the XI terminal and the XO terminal, and generates an oscillation signal OSCO by oscillating the oscillator 3. Specifically, the oscillator circuit 10 receives a signal output from the oscillator 3 via the XI terminal, amplifies the signal, and supplies it to the oscillator 3 via the XO terminal.

[0017] The temperature sensor 30 detects the temperature of the circuit device 2 and outputs a temperature signal having a voltage corresponding to the temperature, and is realized by, for example, a circuit that utilizes the temperature characteristics of a bandgap reference circuit.

[0018] The temperature compensation circuit 32 generates a temperature compensation voltage Vcomp for correcting the frequency-temperature characteristics of the oscillation signal OSCO output from the oscillation circuit 10 based on the temperature signal output from the temperature sensor 30 and temperature compensation data corresponding to the frequency-temperature characteristics of the resonator 3, and supplies the temperature compensation voltage Vcomp to the oscillation circuit 10. The temperature compensation data is supplied to the temperature compensation circuit 32 from the logic circuit 36.

[0019] When the switch circuit 90 is on, the frequency control circuit 34 receives the frequency control signal input from the T4 terminal via the VC terminal. The frequency control circuit 34 generates a frequency control voltage Vafc for controlling the oscillation frequency of the oscillation circuit 10 in accordance with the voltage level of the frequency control signal, and supplies the frequency control voltage Vafc to the oscillation circuit 10.

[0020] The oscillation signal OSCO output from the oscillation circuit 10 has a substantially constant frequency according to the frequency control voltage Vafc at any temperature within a predetermined temperature range due to the temperature compensation voltage Vcomp.

[0021] In this embodiment, the output circuit 20 includes a waveform shaping circuit 21, a frequency dividing circuit 22, a pre-buffer 23, an output buffer 24, a pre-buffer 25, and an output buffer .

[0022] The waveform shaping circuit 21 buffers the oscillation signal OSCO output from the oscillation circuit 10 and outputs a square wave clock signal CK1.

[0023] The frequency divider circuit 22 outputs a clock signal CK2 obtained by dividing the clock signal CK1 output from the waveform shaping circuit 21 by a division ratio corresponding to the division ratio data. The division ratio data is supplied to the frequency divider circuit 22 from the logic circuit 36. When the division ratio is 1, the frequency divider circuit 22 outputs a clock signal CK2 obtained by buffering the clock signal CK1 output from the waveform shaping circuit 21. The clock signal CK2 output from the frequency divider circuit 22 is input in common to the pre-buffer 23 and the pre-buffer 25.

[0024] The pre-buffer 23 outputs a clock signal CK3 obtained by buffering the clock signal CK2 output from the frequency divider circuit 22. The pre-buffer 23 also functions as a level shifter that outputs the clock signal CK3 at a voltage level that matches the input voltage level of the output buffer 24.

[0025] The output buffer 24 buffers the clock signal CK3 output from the pre-buffer 23 and outputs a clock signal having a CMOS (Complementary Metal Oxide Semiconductor) output waveform.

[0026] The pre-buffer 25 buffers the clock signal CK2 output from the frequency divider circuit 22 and outputs the clock signal CK4.

[0027] The output buffer 26 converts the clock signal CK4 output from the pre-buffer 25 into a clock signal having a clipped sine waveform and outputs it.

[0028] In this embodiment, the output node of the output buffer 24, the output node of the output buffer 26, and the OUT terminal are electrically connected. At least one of the output node of the output buffer 24 and the output node of the output buffer 26 becomes high impedance in response to the clock selection data. The clock selection data is supplied from the logic circuit 36 ​​to the output buffer 24 and the output buffer 26.

[0029] When only the output node of the output buffer 26 is in a high impedance state, the clock signal of the CMOS output waveform output from the output buffer 24 is output as the clock signal CKO via the OUT terminal and the T3 terminal to the outside of the oscillator 1. Also, when only the output node of the output buffer 24 is in a high impedance state, the clock signal of the clipped sine waveform output from the output buffer 26 is output as the clock signal CKO to the outside of the oscillator 1 via the OUT terminal and the T3 terminal.

[0030] The RC filter 60 receives the clock signal CK4 output from the pre-buffer 25, and outputs a DC voltage obtained by smoothing the voltage of the clock signal CK4.

[0031] The switch circuits 70, 80, and 90 are turned on or off in response to switch control data, which is supplied from the logic circuit 36 ​​to the switch circuits 70, 80, and 90.

[0032] When the switch circuit 70 is on, the RC filter 60 and one end of the switch circuit 80 are electrically connected, and when the switch circuit 70 is off, the RC filter 60 and one end of the switch circuit 80 are not electrically connected.

[0033] When the switch circuit 80 is on, one end of the switch circuit 70 and the VC terminal are electrically connected, and when the switch circuit 80 is off, one end of the switch circuit 70 and the VC terminal are not electrically connected.

[0034] When the switch circuit 90 is on, the VC terminal and the input node of the frequency control circuit 34 are electrically connected, and when the switch circuit 90 is off, the VC terminal and the input node of the frequency control circuit 34 are not electrically connected.

[0035] The logic circuit 36 ​​controls the operation of each circuit. Specifically, the logic circuit 36 ​​sets the operation mode of the oscillator 1 or the circuit device 2 to one of a plurality of modes including an external communication mode, a normal operation mode, and various inspection modes based on a control signal input to a terminal of the circuit device 2, and performs control according to the set operation mode. In this embodiment, when a control signal of a predetermined pattern is input from the VC terminal within a predetermined period from the start of supply of a power supply voltage to the VDD terminal, the logic circuit 36 ​​sets the operation mode to the external communication mode after the predetermined period has elapsed. For example, the logic circuit 36 ​​may determine the predetermined period as the period from when the oscillator 3 starts oscillating due to the supply of a power supply voltage to when it detects that the oscillation has stabilized, or may count the number of pulses of the oscillation signal OSCO and determine that the predetermined period has elapsed when the count value reaches a predetermined value. Also, for example, the logic circuit 36 ​​may measure the predetermined period based on an output signal of an RC time constant circuit that starts operating due to the supply of a power supply voltage.

[0036] In the external communication mode, the logic circuit 36 ​​outputs clock selection data that sets the outputs of the output buffers 24 and 26 to high impedance, and outputs switch control data that sets the switch circuits 70, 80, and 90 to off. In the external communication mode, a serial clock signal and a serial data signal are input from the VC terminal and the OUT terminal in synchronization with each other. In the external communication mode, the logic circuit 36 ​​outputs, for example, I 2 In accordance with the standard of the Inter-Integrated Circuit (IC) bus, the logic circuit 36 ​​samples the serial data signal at each edge of the serial clock signal. Based on the sampled command and data, the logic circuit 36 ​​performs processes such as setting the operation mode, setting clock selection data and switch control data in each operation mode, and reading and writing data from and to the register 51 or non-volatile memory 52. ​​In this embodiment, the logic circuit 36 ​​performs processes such as setting the operation mode, setting clock selection data and switch control data in each operation mode, and reading and writing data from and to the register 51 or non-volatile memory 52. 2It functions as an interface circuit for a two-wire bus such as an Inter-Integrated Circuit (C) bus, but may also function as an interface circuit for a three-wire or four-wire bus such as a Serial Peripheral Interface (SPI) bus.

[0037] For example, when the logic circuit 36 ​​samples a normal operation mode setting command in the external communication mode, the logic circuit 36 ​​transitions the operation mode from the external communication mode to the normal operation mode. In the normal operation mode, the logic circuit 36 ​​outputs clock selection data for setting only one of the outputs of the output buffers 24 and 26 to high impedance, and outputs switch control data for setting the switch circuits 70 and 80 to OFF and the switch circuit 90 to ON. This electrically disconnects the VC terminal from the RC filter 60, and electrically connects the VC terminal to the frequency control circuit 34. As a result, a clock signal CKO having a frequency according to the voltage of the VC terminal is output from the OUT terminal to the outside via the T3 terminal.

[0038] If a control signal of a predetermined pattern is not input from the VC terminal within a predetermined period of time after the supply of power supply voltage begins, the logic circuit 36 ​​does not set the operation mode to the external communication mode after the predetermined period of time has elapsed, but directly sets it to the normal operation mode.

[0039] Also, for example, when the logic circuit 36 ​​samples a duty ratio check command in the external communication mode, it transitions the operation mode from the external communication mode to a duty ratio check mode, which is one of the check modes. In the duty ratio check mode, the logic circuit 36 ​​outputs switch control data that sets the switch circuits 70 and 80 on and the switch circuit 90 off. This electrically connects the VC terminal to the output node of the RC filter 60, and electrically disconnects the VC terminal from the input node of the frequency control circuit 34. As a result, the DC voltage output from the RC filter 60 is output to the outside from the T4 terminal via the VC terminal, and the external device can calculate the duty ratio of the clock signal CK4 based on the voltage of the T4 terminal.

[0040] The memory circuit 50 is a circuit for storing various types of information, and includes a register 51 and a nonvolatile memory 52. ​​The nonvolatile memory 52 is, for example, a MONOS (Metal Oxide Nitride Oxide Silicon) type memory or an EEPROM (Electrically Erasable Programmable Read-Only Memory). In the manufacturing process of the oscillator 1, various types of information such as temperature compensation data, frequency division ratio data, and clock selection data are stored in the nonvolatile memory 52. ​​When the oscillator 1 is powered on, the various types of information stored in the nonvolatile memory 52 are transferred to the register 51, and the various types of information stored in the register 51 are appropriately supplied to each circuit via the logic circuit 36.

[0041] 1-2. Configuration of the oscillator circuit Fig. 4 is a diagram showing a configuration example of the oscillator circuit 10. As shown in Fig. 4, the oscillator circuit 10 includes a reference voltage circuit 11, a bias current generating circuit 12, capacitance circuits 13 and 14, variable capacitance circuits 15, 16, 17 and 18, a bipolar transistor 101, a resistive element 102 and capacitance elements 103 and 104. Note that the oscillator circuit 10 of this embodiment may be configured such that some of these elements are omitted or modified, or other elements are added.

[0042] The reference voltage circuit 11 includes a plurality of resistance elements 111 and a duty ratio adjustment circuit 112. The plurality of resistance elements 111 are connected in series between a supply line of a power supply voltage VDDL and a ground. The power supply voltage VDDL is supplied from a power supply circuit 40. The reference voltage circuit 11 outputs at least a portion of a plurality of voltages obtained by dividing a voltage between the power supply voltage VDDL and a ground voltage by the plurality of resistance elements 111 as n reference voltages VcgC[n:1] and m reference voltages VcgA[m:1]. Each of n and m is an integer of 2 or more. The integer n and the integer m may be the same or different. At least one of the n reference voltages VcgC[n:1] and at least one of the m reference voltages VcgA[m:1] may be the same. The reference voltages VcgC[n:1] are supplied to the variable capacitance circuits 15 and 16. In addition, the reference voltage VcgA[m:1] is supplied to the variable capacitance circuits 17 and 18.

[0043] The duty ratio adjustment circuit 112 selects one of all or some of the multiple voltages divided by the multiple resistance elements 111 based on the duty ratio adjustment data, and outputs the selected one as the bias voltage Vrefb. The duty ratio adjustment data is stored in the nonvolatile memory 52, and the logic circuit 36 ​​supplies the duty ratio adjustment data transferred from the nonvolatile memory 52 to the register 51 to the duty ratio adjustment circuit 112.

[0044] The bias current generating circuit 12 includes two P-channel MOS (Metal Oxide Semiconductor) transistors 121 and 122 and a constant current source 123 .

[0045] The gate and drain of the MOS transistor 121 are electrically connected, and a power supply voltage VDDL is supplied to the source. The gate of the MOS transistor 122 is electrically connected to the gate of the MOS transistor 121, a power supply voltage VDDL is supplied to the source, and a drain is electrically connected to the collector of the bipolar transistor 101 which is an amplifying element. The gate and drain of the MOS transistor 121 are electrically connected to one end of a constant current source 123. The other end of the constant current source 123 is connected to ground.

[0046] In the bias current generating circuit 12 configured in this manner, the reference current Iref flowing through the constant current source 123 is multiplied by a predetermined amount by a current mirror circuit formed by the MOS transistors 121 and 122, and the resulting current flows between the source and drain of the MOS transistor 122. This current is supplied to the bipolar transistor 101 as the bias current Ibias.

[0047] One end of the capacitive element 103 is electrically connected to the base of the bipolar transistor 101, and the other end is electrically connected to one end of the vibrator 3 via the XI terminal.

[0048] The capacitance element 104 has one end electrically connected to the gate of the MOS transistor 121 and the gate of the MOS transistor 122 , and the other end electrically connected to the base of the bipolar transistor 101 .

[0049] The bipolar transistor 101 has a base electrically connected to one end of the capacitance element 103, a collector electrically connected to the XO terminal, and an emitter grounded. A resistance element 102 is connected between the base and collector of the bipolar transistor 101. A bias current Ibias is supplied to the collector of the bipolar transistor 101.

[0050] An oscillation signal input from the XI terminal is supplied to the gate of the bipolar transistor 101 via the capacitance element 103 and is amplified by the bipolar transistor 101, which is an amplifying element. The amplified oscillation signal is supplied from the collector of the bipolar transistor 101 to the vibrator 3 via the XO terminal. Note that instead of the bipolar transistor 101, a MOS transistor or a CMOS inverter may be used as the amplifying element.

[0051] The oscillator circuit 10 outputs a signal generated at a node between the XI terminal and the other end of the capacitive element 103 as an oscillation signal OSCO. A bias voltage Vrefb is supplied to the node from the duty ratio adjustment circuit 112 of the reference voltage circuit 11. Therefore, the oscillation signal OSCO has a waveform that oscillates around the bias voltage Vrefb, and is input to the waveform shaping circuit 21 of the output circuit 20. Therefore, the duty ratio of the clock signal CK1 output from the waveform shaping circuit 21 changes according to the bias voltage Vrefb, and as a result, the duty ratio of the clock signal CKO output from the output circuit 20 also changes. Since the bias voltage Vrefb becomes a voltage according to the duty ratio adjustment data supplied from the logic circuit 36, the duty ratio of the clock signal CKO can be brought close to a target value by setting appropriate duty ratio adjustment data in the non-volatile memory 52. ​​The target value is, for example, 50%.

[0052] The capacitance circuit 13 includes k capacitance elements 131-1 to 131-k and k switch elements 132-1 to 132-k, where k is an integer equal to or greater than 2. For each integer i between 1 and k, one end of the capacitance element 131-i is electrically connected to the XI terminal and the other end is electrically connected to one end of the switch element 132-i. The other end of the switch element 132-i is electrically connected to the ground.

[0053] The capacitance circuit 14 includes k capacitance elements 141-1 to 141-k and k switch elements 142-1 to 142-k. For each integer i between 1 and k, one end of the capacitance element 141-i is electrically connected to the XO terminal and the other end is electrically connected to one end of the switch element 142-i. The other end of the switch element 142-i is electrically connected to the ground.

[0054] The switch elements 132-1 to 132-k are turned on or off according to the value of each bit of the frequency adjustment data. The capacitive element 131-i is connected between the XI terminal and the ground when the switch element 132-i is on. Similarly, the switch elements 142-1 to 142-k are turned on or off according to the value of each bit of the frequency adjustment data. The capacitive element 141-i is connected between the XO terminal and the ground when the switch element 142-i is on. The frequency adjustment data is stored in the non-volatile memory 52, and the logic circuit 36 ​​supplies the frequency adjustment data transferred from the non-volatile memory 52 to the register 51 to the capacitive circuits 13 and 14.

[0055] The capacitance value of the capacitance circuit 13 is the sum of the capacitance values ​​of the capacitance elements 131-1 to 131-k that are connected between the XI terminal and the ground. The capacitance value of the capacitance circuit 14 is the sum of the capacitance values ​​of the capacitance elements 141-1 to 141-k that are connected between the XO terminal and the ground. Therefore, the capacitance values ​​of the capacitance circuits 13 and 14 change according to the frequency adjustment data. The capacitance circuits 13 and 14 function as load capacitances of the oscillator 3, and the frequency of the oscillation signal OSCO changes according to the capacitance values ​​of the capacitance circuits 13 and 14. As a result, the frequency of the clock signal CKO changes. Therefore, by setting appropriate frequency adjustment data in the non-volatile memory 52, the difference between the frequency of the clock signal CKO at the reference temperature and the target frequency can be minimized. The reference temperature may be, for example, 25°C.

[0056] The variable capacitance circuit 15 includes a capacitance element 151, n variable capacitance elements 152-1 to 152-n, n capacitance elements 153-1 to 153-n, and a resistance element 154. One end of the capacitance element 151 is electrically connected to the XI terminal, and the other end is electrically connected to one end of each of the variable capacitance elements 152-1 to 152-n and one end of the resistance element 154. For each integer i between 1 and n, the other end of the variable capacitance element 152-i is electrically connected to one end of the capacitance element 153-i, and the other end of the capacitance element 153-i is electrically connected to the ground. A reference voltage VcgC[i] is supplied to the other end of the variable capacitance element 152-i and one end of the capacitance element 153-i. A temperature compensation voltage Vcomp is supplied to one end of each of the variable capacitance elements 152-1 to 152-n via the resistance element 154.

[0057] The variable capacitance circuit 16 includes a capacitance element 161, n variable capacitance elements 162-1 to 162-n, n capacitance elements 163-1 to 163-n, and a resistance element 164. One end of the capacitance element 161 is electrically connected to the XO terminal, and the other end is electrically connected to one end of each of the variable capacitance elements 162-1 to 162-n and one end of the resistance element 164. For each integer i between 1 and n, the other end of the variable capacitance element 162-i is electrically connected to one end of the capacitance element 163-i, and the other end of the capacitance element 163-i is electrically connected to the ground. A reference voltage VcgC[i] is supplied to the other end of the variable capacitance element 162-i and one end of the capacitance element 163-i. A temperature compensation voltage Vcomp is supplied to one end of each of the variable capacitance elements 162-1 to 162-n via the resistance element 164.

[0058] The capacitance value of each of the variable capacitance elements 152-1 to 152-n changes according to the temperature compensation voltage Vcomp. Similarly, the capacitance value of each of the variable capacitance elements 162-1 to 162-n changes according to the temperature compensation voltage Vcomp. Therefore, the capacitance values ​​of the variable capacitance circuits 15 and 16 change according to the temperature compensation voltage Vcomp. The variable capacitance circuits 15 and 16 function as load capacitances of the oscillator 3, and the frequency of the oscillation signal OSCO changes according to the capacitance values ​​of the variable capacitance circuits 15 and 16. As a result, the frequency of the clock signal CKO changes. Therefore, by setting appropriate temperature compensation data in the non-volatile memory 52, it is possible to minimize the difference between the frequency of the clock signal CKO and the target frequency at any temperature in a predetermined temperature range.

[0059] The variable capacitance circuit 17 includes a capacitance element 171, m variable capacitance elements 172-1 to 172-m, m capacitance elements 173-1 to 173-n, and a resistance element 174. One end of the capacitance element 171 is electrically connected to the XI terminal, and the other end is electrically connected to one end of each of the variable capacitance elements 172-1 to 172-m and one end of the resistance element 174. For each integer i between 1 and m, the other end of the variable capacitance element 172-i is electrically connected to one end of the capacitance element 173-i, and the other end of the capacitance element 173-i is electrically connected to the ground. A reference voltage VcgA[i] is supplied to the other end of the variable capacitance element 172-i and one end of the capacitance element 173-i. A frequency control voltage Vafc is supplied to one end of each of the variable capacitance elements 172-1 to 172-m via the resistance element 174.

[0060] The variable capacitance circuit 18 includes a capacitance element 181, m variable capacitance elements 182-1 to 182-m, m capacitance elements 183-1 to 183-n, and a resistance element 184. One end of the capacitance element 181 is electrically connected to the XO terminal, and the other end is electrically connected to one end of each of the variable capacitance elements 182-1 to 182-m and one end of the resistance element 184. For each integer i between 1 and m, the other end of the variable capacitance element 182-i is electrically connected to one end of the capacitance element 183-i, and the other end of the capacitance element 183-i is electrically connected to the ground. A reference voltage VcgA[i] is supplied to the other end of the variable capacitance element 182-i and one end of the capacitance element 183-i. A frequency control voltage Vafc is supplied to one end of each of the variable capacitance elements 182-1 to 182-m via the resistance element 184.

[0061] The capacitance value of each of the variable capacitance elements 172-1 to 172-m changes according to the frequency control voltage Vafc. Similarly, the capacitance value of each of the variable capacitance elements 182-1 to 182-m changes according to the frequency control voltage Vafc. Therefore, the capacitance values ​​of the variable capacitance circuits 17 and 18 change according to the frequency control voltage Vafc. The variable capacitance circuits 17 and 18 function as load capacitances of the oscillator 3, and the frequency of the oscillation signal OSCO changes according to the capacitance values ​​of the variable capacitance circuits 17 and 18. As a result, the frequency of the clock signal CKO changes. Therefore, the frequency of the clock signal CKO can be changed according to the voltage applied to the T4 terminal.

[0062] For example, the capacitance elements 103, 104, 131-1 to 131-k, 141-1 to 141-k, 151, 153-1 to 153-n, 161, 163-1 to 163-n, 171, 173-1 to 173-m, 181, 183-1 to 183-m may be MIM (Metal Insulator Metal) type capacitors using metal for two electrodes, or PIP (Poly Insulator Poly) type capacitors using polysilicon for two electrodes. Also, for example, the variable capacitance elements 152-1 to 152-n, 162-1 to 162-n, 172-1 to 172-m, 182-1 to 182-m may be varactors in which the source and drain of a MOS transistor are connected.

[0063] 1-3. Duty ratio inspection method As described above, in this embodiment, the duty ratio of the clock signal CKO can be brought closer to a target value by setting appropriate duty ratio adjustment data in the non-volatile memory 52. ​​In order to calculate appropriate duty ratio adjustment data, for example, it is necessary to obtain the duty ratio of the clock signal CKO in a state where the duty ratio adjustment data is set to an initial value.

[0064] FIG. 5 is a diagram showing an example of the voltage waveforms of the clock signal CKO output from the T3 terminal and the clock signal CK4 output from the pre-buffer 25. In the example of FIG. 5, the clock signals CKO and CK4 are both waveforms with a duty ratio of 50%. FIG. 6 is a diagram showing an example of the relationship between the duty ratio of the clock signal CKO and the DC bias, and FIG. 7 is a diagram showing an example of the relationship between the duty ratio of the clock signal CK4 and the DC bias. The DC bias is an average value of the voltage, and the DC bias of the clock signal CK4 corresponds to the DC voltage output from the RC filter 60. The DC bias of the clock signal CKO corresponds to the DC voltage output from the RC filter if the RC filter is connected to the T3 terminal.

[0065] As described above, the clock signal CKO output from the output buffer 26 is a signal with a clipped sine waveform. Therefore, as shown in FIG. 5, the clock signal CKO with the clipped sine waveform has gentle rising and falling edges. Also, as described above, the clock signal CKO output from the output buffer 24 is a signal with a CMOS output waveform. However, if the load of the external circuit connected to the T3 terminal is large, the clock signal CKO with the CMOS output waveform has gentle rising and falling edges. Therefore, the oscillation amplitude of the clock signal CKO output from the T3 terminal fluctuates greatly. As a result, as shown in FIG. 6, the duty ratio of the clock signal CKO and the DC bias do not have a linear relationship, and it is difficult to accurately calculate the duty ratio from the DC bias.

[0066] On the other hand, in this embodiment, the pre-buffer 25 drives the output buffer 26 and the RC filter 60, which have a small load, and has a higher driving capability than the waveform shaping circuit 21. Therefore, as shown in FIG. 5, the clock signal CK4 output from the pre-buffer 25 becomes a square wave signal, and the rise time of the clock signal CK4 is shorter than the rise time of the clock signal CKO, and the fall time of the clock signal CK4 is shorter than the fall time of the clock signal CKO. The rise time is the time from when the voltage reaches a specified lower limit value to when it reaches a specified upper limit value, and the fall time is the time from when the voltage reaches the upper limit value to when it reaches the lower limit value. The method of defining the upper limit value and the lower limit value differs depending on the type of signal waveform, product specifications, etc. As a typical example, the lower limit value is 20% of the power supply voltage, and the upper limit value is 80% of the power supply voltage.

[0067] In this way, the clock signal CK4 has a waveform with steep rising and falling edges and an almost constant oscillation amplitude. As a result, as shown in Fig. 7, the duty ratio of the clock signal CK4 and the DC bias have a linear relationship, and the duty ratio can be accurately calculated from the DC bias. Furthermore, a correlation between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO can be obtained from the simulation results of the operation of the oscillator 1 and the evaluation results of the oscillator 1, and therefore the duty ratio of the clock signal CKO can be accurately calculated from the duty ratio of the clock signal CK4 based on the correlation.

[0068] Therefore, in this embodiment, the input node of the RC filter 60 is connected to the output node of the pre-buffer 25, not to the output nodes of the output buffers 24 and 26, and the DC voltage output from the RC filter 60 corresponds to the DC bias of the clock signal CK4. In the duty ratio check mode, the output node of the RC filter 60 is electrically connected to the T3 terminal, so that the external device can calculate the duty ratio of the clock signal CK4 based on the voltage of the T3 terminal from the relationship in FIG. 7. Furthermore, the external device can accurately calculate the duty ratio of the clock signal CKO based on the correlation between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO. This clock signal CKO may be a clock signal with a clipped sine waveform output from the output buffer 26, or may be a clock signal with a CMOS output waveform output from the output buffer 24.

[0069] The input node of the RC filter 60 may be connected to the output node of the pre-buffer 23. In this embodiment, the pre-buffer 23 drives only the output buffer 24 and has a higher driving capability than the waveform shaping circuit 21, so that the clock signal CK3 output from the pre-buffer 23 is a square wave signal. Therefore, the duty ratio of the clock signal CK3 and the DC bias have a linear relationship.

[0070] FIG. 8 is a diagram showing the details of each circuit on the signal propagation path from the XI terminal to the T3 terminal or the T4 terminal in the duty ratio check mode.

[0071] 8, the waveform shaping circuit 21 has a buffer circuit 211, which outputs a clock signal CK1 based on the oscillation signal OSCO. Specifically, the buffer circuit 211 receives the oscillation signal OSCO from an XI terminal via a capacitive element 103, and outputs the clock signal CK1.

[0072] The frequency divider circuit 22 outputs a clock signal CK2 based on the oscillation signal OSCO. Specifically, the frequency divider circuit 22 receives the clock signal CK1 based on the oscillation signal OSCO, and outputs the clock signal CK2 obtained by dividing the clock signal CK1.

[0073] The pre-buffer 25 has buffer circuits 251 and 252, and the buffer circuit 252 outputs a clock signal CK4 based on the oscillation signal OSCO. Specifically, a clock signal CK2 based on the oscillation signal OSCO is input to the buffer circuit 251, and the buffer circuit 252 receives the output signal of the buffer circuit 251 and outputs the clock signal CK4.

[0074] The output buffer 26 has a buffer circuit 261, which outputs a clock signal CKO based on the clock signal CK4. Specifically, the buffer circuit 261 receives the clock signal CK4 output from the buffer circuit 252 and outputs the clock signal CKO. The OUT terminal is electrically connected to a node N2 at which the buffer circuit 261 outputs the clock signal CKO, and the clock signal CKO is output to the outside of the oscillator 1 via the OUT terminal and the T3 terminal.

[0075] The RC filter 60 is electrically connected between a node N1, at which the buffer circuit 252 outputs the clock signal CK4, and the switch circuit 70, and is a low-pass filter constituted by a resistive element 61 and a capacitive element 62. One end of the resistive element 61 is electrically connected to the node N1, and the capacitive element 62 is connected between the other end of the resistive element 61 and the ground. A DC voltage that smoothes the voltage of the clock signal CK4 is output from a node N3 to which the other end of the resistive element 61 and one end of the capacitive element 62 are connected.

[0076] The switch circuit 70 is a switch circuit that electrically connects or disconnects the node N1 and the VC terminal, and has a transmission gate 71 and an N-channel MOS transistor 72. Similarly, the switch circuit 80 is a switch circuit that electrically connects or disconnects the node N1 and the VC terminal, and has a transmission gate 81.

[0077] One end of the transmission gate 71 is connected to the node N3, and the MOS transistor 72 is connected between the other end of the transmission gate 71 and the ground. One end of the transmission gate 81 is connected to a node N4 to which the other end of the transmission gate 71 and the drain of the MOS transistor 72 are connected, and the other end is connected to the VC terminal. Therefore, the VC terminal can be electrically connected to the node N1 via the resistive element 61 and the transmission gates 71 and 81.

[0078] In the normal operation mode and the external communication mode, the transmission gates 71 and 81 are both turned off, and the node N1 is electrically disconnected from the VC terminal. When the transmission gate 71 is turned off, the MOS transistor 72 is turned on, and the node N4 is electrically connected to the ground.

[0079] On the other hand, in the duty ratio test mode, the transmission gates 71 and 81 are both turned on, and the node N1 and the VC terminal are electrically connected via the resistive element 61 and the transmission gates 71 and 81. The voltage of the T4 terminal connected to the VC terminal becomes a DC voltage obtained by smoothing the voltage of the clock signal CK4.

[0080] The T4 terminal is connected to inspection device 300, which is an external device to oscillator 1. Inspection device 300 sets oscillator 1 to a duty ratio inspection mode and measures the voltage at the T4 terminal. Then, inspection device 300 can calculate the duty ratio of clock signal CK4 based on the measured value of the voltage at the T4 terminal, and calculate the duty ratio of clock signal CKO based on the duty ratio of clock signal CK4.

[0081] Here, the buffer circuit 252 has a higher driving capability than the buffer circuit 211 electrically connected between the output node of the oscillation circuit 10 from which the oscillation signal OSCO is output and the buffer circuit 252. Therefore, the clock signal CK4 output from the buffer circuit 252 to the node N1 has a shorter rise time and fall time than the clock signal CK1 output from the buffer circuit 211. Therefore, the clock signal CK4 has a higher linearity in the relationship between the duty ratio and the DC bias than the clock signal CK1, and the inspection device 300 can accurately calculate the duty ratio of the clock signal CK4 based on the measured value of the voltage of the T4 terminal. Furthermore, since the node N1 is the input node of the buffer circuit 261, the difference between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO is small, and the inspection device 300 can accurately calculate the duty ratio of the clock signal CKO based on the duty ratio of the clock signal CK4.

[0082] In this embodiment, the clock signal CK4 is an example of a first clock signal, and the clock signal CKO is an example of a second clock signal. The buffer circuit 252 is an example of a first buffer circuit, the buffer circuit 261 is an example of a second buffer circuit, and the buffer circuit 211 is an example of a third buffer circuit. The node N1 is an example of a first node, and the node N2 is an example of a second node. The VC terminal is an example of a first terminal, and the OUT terminal is an example of a second terminal.

[0083] Fig. 9 is a flowchart showing an example of the procedure of a method for testing the duty ratio of the clock signal CKO output from the oscillator 1 of the first embodiment. Fig. 10 is a diagram showing an example of voltage waveforms of control signals of each terminal and each switch when testing the duty ratio according to the flowchart of Fig. 9.

[0084] In the example of Fig. 9, first, the inspection device 300 supplies a power supply voltage to the T1 terminal of the oscillator 1 (step S1). As shown in Fig. 10, step S1 causes the T1 terminal to rise from the ground voltage to a desired voltage. In addition, various information including the duty ratio adjustment data stored in the non-volatile memory 52 is transferred to the register 51 and supplied from the logic circuit 36 ​​to each circuit.

[0085] Next, the inspection device 300 supplies a control signal to the T4 terminal of the oscillator 1, and sets the oscillator 1 to the external communication mode (step S2). That is, as shown in Fig. 10, the inspection device 300 supplies a signal of a predetermined pattern to the T4 terminal of the oscillator 1 within a predetermined period after supplying a power supply voltage to the T1 terminal, and sets the oscillator 1 to the external communication mode.

[0086] Next, the inspection device 300 supplies control signals to the T3 terminal and the T4 terminal of the oscillator 1, and sets the oscillator 1 to the duty ratio inspection mode (step S3). That is, as shown in FIG. 10, in the external communication mode, the inspection device 300 supplies a serial clock signal to the T3 terminal, supplies a duty ratio inspection command as a serial data signal to the T4 terminal, and sets the oscillator 1 to the duty ratio inspection mode. As shown in FIG. 10, the oscillator 1 transitions from the external communication mode to the duty ratio inspection mode by step S3, and the control signals of the switch circuits 70 and 80 change from low level to high level, and the control signal of the switch circuit 90 changes from high level to low level. As a result, both the switch circuits 70 and 80 are turned on, the T4 terminal and the output node of the RC filter 60 are electrically connected, and the voltage of the T4 terminal becomes a DC voltage output from the RC filter 60.

[0087] Next, the inspection device 300 measures the voltage at the T4 terminal of the oscillator 1 (step S4). That is, the inspection device 300 measures the DC voltage output from the RC filter 60.

[0088] Next, the inspection device 300 calculates the duty ratio of the clock signal CK4 from the voltage of the T4 terminal measured in step S4 (step S5).

[0089] Next, the inspection device 300 calculates the duty ratio of the clock signal CKO from the duty ratio of the clock signal CK4 calculated in step S5 (step S6).

[0090] Then, if the difference between the duty ratio of the clock signal CKO calculated in step S6 and the target value is equal to or less than the threshold value (Y in step S7), the inspection device 300 ends the process. The target value is, for example, 50%. The threshold value is set to, for example, the adjustment resolution of the duty ratio of the clock signal CKO by the duty ratio adjustment data.

[0091] Furthermore, if the difference between the duty ratio of the clock signal CKO calculated in step S6 and the target value is greater than a threshold value (N in step S7), the inspection device 300 calculates, from the difference, duty ratio adjustment data that brings the duty ratio of the clock signal CKO closest to the target value (step S8), and ends the process.

[0092] It should be noted that the inspection device 300 writes necessary information such as the duty ratio adjustment data calculated in step S8 into the non-volatile memory 52, for example, after a series of inspections is completed.

[0093] 1-4.Effects As described above, in the oscillator 1 of the first embodiment, in the circuit device 2, the node N1 at which the buffer circuit 252 of the pre-buffer 25 outputs the clock signal CK4 is electrically connected to the VC terminal, so that the voltage of the VC terminal becomes a DC voltage obtained by smoothing the clock signal CK4 by the RC filter 60. The rise time and fall time of this clock signal CK4 are shorter than the rise time and fall time of the clock signal CKO output from the buffer circuit 261, which is the output buffer 26, to the outside via the OUT terminal and the T3 terminal. Therefore, the correlation between the duty ratio of the clock signal CK4 and the DC bias is closer to linear than the correlation between the duty ratio of the clock signal CKO and the DC bias. Therefore, the inspection device 300 can calculate the duty ratio of the clock signal CK4 with high accuracy based on the voltage of the T4 terminal connected to the VC terminal, and further calculate the duty ratio of the clock signal CKO with high accuracy based on the relationship between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO.

[0094] Furthermore, according to the oscillator 1 of the first embodiment, in the circuit device 2, the resistive element 61 constituting the RC filter 60 reduces the adverse effect of the capacitance of the transmission gate 71 constituting the switch circuit 70 on the buffer circuit 261, which is the output buffer 26, thereby reducing the risk of an increase in noise components in the clock signal CKO and a deterioration in the duty ratio.

[0095] According to the oscillator 1 of the first embodiment, in the normal operation mode, the node N1 is electrically disconnected from the VC terminal and the T4 terminal, so that even if a signal is input from the T4 terminal, the signal propagates from the T4 terminal to the node N1 via the VC terminal, which reduces the possibility of an increase in noise components in the clock signal CKO and a deterioration in the duty ratio. Conversely, the possibility of the circuit device 2 malfunctioning due to the smoothed DC voltage of the clock signal CK4 propagating to the frequency control circuit 34 electrically connected to the VC terminal and adversely affecting the frequency control circuit 34 is also reduced. According to the oscillator 1 of the first embodiment, the T4 terminal and the VC terminal are used in both the normal operation mode and the duty ratio inspection mode, so that a dedicated terminal for outputting the smoothed DC voltage of the clock signal CK4 to the outside is not required.

[0096] Furthermore, in the oscillator 1 of the first embodiment, since the circuit device 2 has the RC filter 60, in order to calculate the duty ratio of the clock signal CK4, it is not necessary to provide a resistive element or a capacitive element that constitutes an RC filter outside the circuit device 2. Therefore, according to the oscillator 1 of the first embodiment, the cost required for constructing an inspection system is reduced.

[0097] In the oscillator 1 of the first embodiment, the buffer circuit 252 of the pre-buffer 25 in the circuit device 2 has a higher driving capability than the buffer circuit 211 which is the waveform shaping circuit 21. That is, the clock signal CK4 output from the buffer circuit 252 has a shorter rise time and fall time than the clock signal CK1 output from the buffer circuit 211. Therefore, the clock signal CK4 has a higher linearity in the relationship between the duty ratio and the DC bias than the clock signal CK1. Therefore, the inspection device 300 can calculate the duty ratio of the clock signal CKO with high accuracy based on the voltage of the T4 terminal, and further calculate the duty ratio of the clock signal CKO with high accuracy based on the relationship between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO.

[0098] Furthermore, according to the oscillator 1 of the first embodiment, in the circuit device 2, the node N1 to which the buffer circuit 252 outputs the clock signal CK4 is the input node of the buffer circuit 261. That is, since the node N1 is close to the output node of the buffer circuit 261, the difference between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO is small. Therefore, the inspection device 300 can accurately calculate the duty ratio of the clock signal CKO based on the duty ratio of the clock signal CK4.

[0099] 2. Second embodiment In the oscillator 1 of the first embodiment, the T4 terminal and the VC terminal to which a voltage for controlling the frequency of the clock signal CKO is input in the normal operation mode are also used as terminals for outputting the output voltage of the RC filter 60 in the duty ratio inspection mode. In contrast, the oscillator 1 of the second embodiment is provided with a dedicated external terminal for outputting the output voltage of the RC filter 60. Hereinafter, for the oscillator 1 of the second embodiment, the same reference numerals are used for configurations similar to those of the first embodiment, and descriptions similar to those of the first embodiment are omitted or simplified, and mainly differences from the first embodiment will be described.

[0100] 11 is a functional block diagram of the oscillator 1 of the second embodiment. As shown in FIG. 11, the oscillator 1 of the second embodiment has a T5 terminal as an external terminal 6 in addition to the T1 terminal, the T2 terminal, the T3 terminal, and the T4 terminal. The circuit device 2 has a TST terminal as an external connection terminal in addition to the VDD terminal, the VSS terminal, the OUT terminal, the VC terminal, the XI terminal, and the XO terminal. The T5 terminal and the TST terminal are electrically connected, and the TST terminal and the output node of the RC filter 60 are electrically connected. Therefore, the DC voltage output from the RC filter 60 is output from the T5 terminal to the outside via the TST terminal, and the external device can calculate the duty ratio of the clock signal CK4 based on the voltage of the T5 terminal.

[0101] The T5 terminal and the TST terminal are dedicated terminals for outputting the DC voltage output from the RC filter 60. Therefore, unlike the first embodiment, the circuit device 2 does not need to include the switch circuits 70, 80. Furthermore, without the switch circuits 70, 80, a DC voltage is output from the T5 terminal even in the normal operation mode, so the oscillator 1 and the circuit device 2 do not need to have a duty ratio check mode.

[0102] The other configurations of the oscillator 1 of the second embodiment are similar to those of the oscillator 1 of the first embodiment, and therefore the description thereof will be omitted.

[0103] Fig. 12 is a diagram showing the details of each circuit on the signal propagation path from the XI terminal to the T3 terminal or the T5 terminal. In Fig. 12, the configuration of each circuit on the signal propagation path from the XI terminal to the T3 terminal is the same as that in Fig. 8, so the description thereof will be omitted.

[0104] 12, the RC filter 60 is a low-pass filter composed of a resistive element 61 and a capacitive element 62, and is electrically connected between a node N1 and a T4 terminal. One end of the resistive element 61 is electrically connected to a node N1 at which the buffer circuit 252 outputs a clock signal CK4, and the capacitive element 62 is connected between the other end of the resistive element 61 and the ground. The node to which the other end of the resistive element 61 and one end of the capacitive element 62 are connected is connected to the TST terminal. The node N1 and the TST terminal are electrically connected via the resistive element 61, and the voltage of the T5 terminal connected to the TST terminal becomes a DC voltage obtained by smoothing the voltage of the clock signal CK1 by the RC filter 60.

[0105] The T5 terminal is connected to an inspection device 300 that is an external device to the oscillator 1. The inspection device 300 measures the voltage of the T5 terminal, calculates the duty ratio of the clock signal CK4 based on the measured value of the voltage of the T5 terminal, and can calculate the duty ratio of the clock signal CKO based on the duty ratio of the clock signal CK4.

[0106] In this embodiment, the clock signal CK4 is an example of a first clock signal, and the clock signal CKO is an example of a second clock signal. The buffer circuit 252 is an example of a first buffer circuit, the buffer circuit 261 is an example of a second buffer circuit, and the buffer circuit 211 is an example of a third buffer circuit. The node N1 is an example of a first node, and the node N2 is an example of a second node. The TST terminal is an example of a first terminal, and the OUT terminal is an example of a second terminal.

[0107] FIG. 13 is a flow chart showing an example of the procedure of a method for testing the duty ratio of the clock signal CKO output from the oscillator 1 of the second embodiment.

[0108] 13, first, the inspection device 300 supplies a power supply voltage to the T1 terminal of the oscillator 1 (step S11). By step S11, the T1 terminal rises from the ground voltage to a desired voltage. In addition, various information including the duty ratio adjustment data stored in the non-volatile memory 52 is transferred to the register 51 and supplied from the logic circuit 36 ​​to each circuit.

[0109] Next, the inspection device 300 waits until a predetermined time has elapsed (step S12). For example, the predetermined time is set to be equal to or longer than the time required for the oscillation of the vibrator 3 to stabilize.

[0110] Next, the inspection device 300 measures the voltage of the T5 terminal of the oscillator 1 (step S13). That is, the inspection device 300 measures the DC voltage output from the RC filter 60.

[0111] Next, the inspection device 300 calculates the duty ratio of the clock signal CK4 from the voltage of the T5 terminal measured in step S13 (step S14).

[0112] Next, the inspection device 300 calculates the duty ratio of the clock signal CKO from the duty ratio of the clock signal CK4 calculated in step S14 (step S15).

[0113] Then, if the difference between the duty ratio of the clock signal CKO calculated in step S15 and the target value is equal to or less than the threshold value (Y in step S16), the inspection device 300 ends the process. The target value is, for example, 50%. The threshold value is set to, for example, the adjustment resolution of the duty ratio of the clock signal CKO by the duty ratio adjustment data.

[0114] Furthermore, if the difference between the duty ratio of the clock signal CKO calculated in step S15 and the target value is greater than a threshold value (N in step S16), the inspection device 300 calculates, from the difference, duty ratio adjustment data that brings the duty ratio of the clock signal CKO closest to the target value (step S17), and ends the process.

[0115] After a series of inspections is completed, the inspection device 300 writes necessary information such as the duty ratio adjustment data calculated in step S17 into the non-volatile memory 52.

[0116] In the oscillator 1 of the second embodiment described above, in the circuit device 2, the node N1 at which the buffer circuit 252 of the pre-buffer 25 outputs the clock signal CK4 is electrically connected to the TST terminal, so that the voltage of the TST terminal becomes a DC voltage obtained by smoothing the clock signal CK4 by the RC filter 60. The rise time and fall time of this clock signal CK4 are shorter than the rise time and fall time of the clock signal CKO output from the buffer circuit 261, which is the output buffer 26, to the outside via the OUT terminal and the T3 terminal. Therefore, the correlation between the duty ratio of the clock signal CK4 and the DC bias is closer to linear than the correlation between the duty ratio of the clock signal CKO and the DC bias. Therefore, the inspection device 300 can calculate the duty ratio of the clock signal CK4 with high accuracy based on the voltage of the T5 terminal connected to the TST terminal, and further calculate the duty ratio of the clock signal CKO with high accuracy based on the relationship between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO.

[0117] Furthermore, according to the oscillator 1 of the second embodiment, the T5 terminal and the TST terminal are used as dedicated terminals for outputting the smoothed DC voltage of the clock signal CK4 to the outside, thereby reducing the risk that the smoothed DC voltage of the clock signal CK4 will propagate to a circuit electrically connected to a terminal other than the T5 terminal and the TST terminal and adversely affect the circuit, causing the circuit device 2 to malfunction.

[0118] Furthermore, in the oscillator 1 of the second embodiment, since the circuit device 2 has the RC filter 60, in order to calculate the duty ratio of the clock signal CK4, it is not necessary to provide a resistive element or a capacitive element that constitutes an RC filter outside the circuit device 2. Therefore, according to the oscillator 1 of the second embodiment, the cost required for constructing an inspection system is reduced.

[0119] In addition to the above-mentioned effects, the oscillator 1 of the second embodiment also achieves the same effects as the oscillator 1 of the first embodiment described above.

[0120] 3. Third embodiment The oscillator 1 of the first embodiment includes an RC filter 60 that smoothes the voltage of the clock signal CK4. In contrast, the oscillator 1 of the third embodiment does not include an RC filter 60 that smoothes the voltage of the clock signal CK4. Hereinafter, for the oscillator 1 of the third embodiment, the same reference numerals are used for configurations similar to those of the first embodiment, and descriptions similar to those of the first embodiment are omitted or simplified, and mainly differences from the first embodiment will be described.

[0121] FIG. 14 is a functional block diagram of the oscillator 1 of the third embodiment. As shown in FIG. 14, in the oscillator 1 of the third embodiment, the circuit device 2 includes a resistive element 63. One end of the resistive element 63 is connected to the output node of the pre-buffer 25, and the other end of the resistive element 63 is electrically connected to the VC terminal when both the switch circuits 70 and 80 are turned on. In this embodiment, in the duty ratio inspection mode, the switch circuits 70 and 80 are turned on and the switch circuit 90 is turned off, so that the VC terminal and the output node of the pre-buffer 25 are electrically connected via the resistive element 63, and the VC terminal and the input node of the frequency control circuit 34 are electrically disconnected. As a result, the clock signal CK4 output from the pre-buffer 25 is output to the outside from the T4 terminal via the VC terminal. Then, the external device calculates the duty ratio of the clock signal CK4 output from the T4 terminal.

[0122] The other configurations of the oscillator 1 of the third embodiment are similar to those of the oscillator 1 of the first embodiment, and therefore the description thereof will be omitted.

[0123] Fig. 15 is a diagram showing the details of each circuit on the signal propagation path from the XI terminal to the T3 terminal or the T4 terminal. In Fig. 15, the configuration of each circuit on the signal propagation path from the XI terminal to the T3 terminal is the same as that in Fig. 8, so the description thereof will be omitted.

[0124] The resistive element 63 is electrically connected between the switch circuit 70 and a node N1 at which the buffer circuit 252 outputs the clock signal CK4.

[0125] The VC terminal can be electrically connected to the node N1 via the resistive element 61 and the transmission gates 71 and 81.

[0126] In the normal operation mode and the external communication mode, the transmission gates 71 and 81 are both turned off, and the node N1 is electrically disconnected from the VC terminal. When the transmission gate 71 is turned off, the MOS transistor 72 is turned on, and the node N4 is electrically connected to the ground.

[0127] On the other hand, in the duty ratio test mode, the transmission gates 71 and 81 are both turned on, and the node N1 and the VC terminal are electrically connected via the resistive element 63 and the transmission gates 71 and 81.

[0128] Outside the oscillator 1, a capacitive element 301 is connected between the T4 terminal and the ground, and when the transmission gates 71 and 81 are both turned on, an RC filter is formed by the resistive element 63 and the capacitive element 301. Therefore, in the duty ratio check mode, the voltage of the T4 terminal becomes a DC voltage that is a smoothed version of the voltage of the clock signal CK4.

[0129] Furthermore, the T4 terminal is connected to inspection device 300, which is an external device to oscillator 1. Inspection device 300 sets oscillator 1 to a duty ratio inspection mode and measures the voltage at the T4 terminal. Then, inspection device 300 can calculate the duty ratio of clock signal CK4 based on the measured value of the voltage at the T4 terminal, and calculate the duty ratio of clock signal CKO based on the duty ratio of clock signal CK4.

[0130] In this embodiment, the clock signal CK4 is an example of a first clock signal, and the clock signal CKO is an example of a second clock signal. The buffer circuit 252 is an example of a first buffer circuit, the buffer circuit 261 is an example of a second buffer circuit, and the buffer circuit 211 is an example of a third buffer circuit. The node N1 is an example of a first node, and the node N2 is an example of a second node. The VC terminal is an example of a first terminal, and the OUT terminal is an example of a second terminal.

[0131] A flowchart showing an example of the procedure of the method for testing the duty ratio of the clock signal CKO output from the oscillator 1 of the third embodiment is similar to that shown in FIG. 9, and therefore illustration and description thereof will be omitted.

[0132] In the oscillator 1 of the third embodiment described above, when the node N1 at which the buffer circuit 252 of the pre-buffer 25 outputs the clock signal CK4 is electrically connected to the VC terminal in the circuit device 2, the resistive element 63 and the capacitive element 301 connected to the T4 terminal form an RC filter. As a result, the voltage of the T4 terminal becomes a DC voltage obtained by smoothing the clock signal CK4 by the RC filter. The rise time and fall time of this clock signal CK4 are shorter than the rise time and fall time of the clock signal CKO output from the buffer circuit 261, which is the output buffer 26, to the outside via the OUT terminal and the T3 terminal. Therefore, the correlation between the duty ratio of the clock signal CK4 and the DC bias is closer to linear than the correlation between the duty ratio of the clock signal CKO and the DC bias. Therefore, the inspection device 300 can calculate the duty ratio of the clock signal CK4 with high accuracy based on the voltage of the T4 terminal, and further calculate the duty ratio of the clock signal CKO with high accuracy based on the relationship between the duty ratio of the clock signal CK4 and the duty ratio of the clock signal CKO.

[0133] Furthermore, according to the oscillator 1 of the third embodiment, in the circuit device 2, the adverse effect of the capacitance of the transmission gate 71 constituting the switch circuit 70 on the buffer circuit 261 is reduced by the resistive element 63, thereby reducing the risk of an increase in noise components in the clock signal CKO and a deterioration in the duty ratio.

[0134] According to the oscillator 1 of the third embodiment, in the normal operation mode, the node N1 is electrically disconnected from the VC terminal and the T4 terminal, so that even if a signal is input from the T4 terminal, the signal propagates from the T4 terminal to the node N1 via the VC terminal, reducing the possibility of an increase in noise components in the clock signal CKO and a deterioration in the duty ratio. Conversely, the clock signal CK4 propagates to the frequency control circuit 34 electrically connected to the VC terminal and adversely affects the frequency control circuit 34, reducing the possibility of the circuit device 2 malfunctioning. According to the oscillator 1 of the third embodiment, the T4 terminal and the VC terminal are used in both the normal operation mode and the duty ratio inspection mode, eliminating the need for a dedicated terminal for outputting the clock signal CK4 to the outside.

[0135] In addition to the above-mentioned effects, the oscillator 1 of the third embodiment also has the same effects as those of the oscillator 1 of the first embodiment.

[0136] 4. Variations The present invention is not limited to the present embodiment, and various modifications are possible within the scope of the present invention.

[0137] In the oscillator 1 of the third embodiment described above, the T4 terminal and the VC terminal to which a voltage for controlling the frequency of the clock signal CKO is input in the normal operation mode are also used as terminals for outputting the output voltage of the RC filter 60 in the duty ratio check mode. In contrast, the oscillator 1 of the third embodiment may be modified to include a dedicated external terminal for outputting the output voltage of the RC filter 60, similar to the oscillator 1 of the second embodiment.

[0138] Furthermore, in each of the above embodiments, a serial clock signal is input to the circuit device 2 from the OUT terminal, and a serial data signal is input to the circuit device 2 from the VC terminal, but the terminals to which the serial clock signal and the serial data signal are input may be terminals other than these.

[0139] Furthermore, in each of the above embodiments, the clock signal output from output buffer 24 or the clock signal output from output buffer 26 is output to the outside from a single external terminal, the T3 terminal, but these clock signals may be output from different external terminals.

[0140] Furthermore, the oscillator 1 in each of the above embodiments is an oscillator having a temperature compensation function and a frequency control function, such as a VC-TCXO (Voltage Controlled Temperature Compensated Crystal Oscillator), but it may also be a simple oscillator without a temperature compensation function or a frequency control function, such as an SPXO (Simple Packaged Crystal Oscillator), an oscillator having a temperature compensation function, such as a TCXO (Temperature Compensated Crystal Oscillator), an oscillator having a frequency control function, such as a VCXO (Voltage Controlled Crystal Oscillator), or an oscillator having a temperature control function, such as an OCXO (Oven Controlled Crystal Oscillator).

[0141] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be appropriately combined.

[0142] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0143] The following can be derived from the above-described embodiment and modifications.

[0144] One aspect of the circuit device is an oscillator circuit for generating an oscillation signal; a first buffer circuit that outputs a first clock signal based on the oscillation signal; a second buffer circuit that outputs a second clock signal based on the first clock signal; a first terminal electrically connectable to a first node at which the first buffer circuit outputs the first clock signal; the second buffer circuit includes a second terminal electrically connected to a second node at which the second buffer circuit outputs the second clock signal; The rise time of the first clock signal is shorter than the rise time of the second clock signal.

[0145] In this circuit device, a first node at which the first buffer circuit outputs a first clock signal is electrically connected to a first terminal, so that a signal based on the first clock signal is output from the first terminal to the outside. The rise time of this first clock signal is shorter than the rise time of a second clock signal output from the second buffer circuit to the outside via the second terminal. Therefore, the correlation between the duty ratio of the first clock signal and the DC bias is closer to linear than the correlation between the duty ratio of the second clock signal and the DC bias. Therefore, the external device can, for example, calculate the duty ratio of the first clock signal with high accuracy from the signal based on the first clock signal output to the outside from the first terminal, and further calculate the duty ratio of the second clock signal with high accuracy based on the relationship between the duty ratio of the first clock signal and the duty ratio of the second clock signal.

[0146] One aspect of the circuit device is The semiconductor device may further include a switch circuit that electrically connects and disconnects the first node and the first terminal.

[0147] In this circuit device, the first node and the first terminal are electrically connected or disconnected by the switch circuit, and when the first node and the first terminal are electrically connected, the operation mode is set to output a signal based on the first clock signal to the outside, and when the first node and the first terminal are electrically disconnected, the operation mode is set to a normal operation mode or the like. Therefore, according to this circuit device, for example, in the normal operation mode, the first node and the first terminal are electrically disconnected, so that even if a signal is input from the first terminal, the risk of an increase in noise components of the second clock signal and a deterioration in the duty ratio due to the signal propagating from the first terminal to the first node is reduced. Conversely, the risk of the signal based on the first clock signal propagating to a circuit electrically connected to the first terminal and adversely affecting the circuit is also reduced, causing the circuit device to malfunction. Furthermore, according to this circuit device, the first terminal is used both in an operation mode in which a signal based on the first clock signal is output to the outside and in a normal operation mode, etc., so that a dedicated terminal for outputting a signal based on the first clock signal to the outside is not required.

[0148] One aspect of the circuit device is The input / output terminal may further include a resistive element electrically connected between the first node and the switch circuit.

[0149] According to this circuit device, the adverse effect of the capacitance of the switch circuit on the second buffer circuit is reduced by the resistive element, so that the risk of an increase in noise components in the second clock signal and a deterioration in the duty ratio are reduced.

[0150] One aspect of the circuit device is The amplifier may include an RC filter electrically connected between the first node and the switch circuit.

[0151] In this circuit device, when the first node and the first terminal are electrically connected by the switch circuit, the voltage of the first terminal becomes a DC voltage obtained by smoothing the first clock signal by the RC filter. Therefore, the external device can, for example, calculate the duty ratio of the first clock signal with high accuracy based on the voltage of the first terminal, and further calculate the duty ratio of the second clock signal with high accuracy based on the relationship between the duty ratio of the first clock signal and the duty ratio of the second clock signal.

[0152] Furthermore, according to this circuit device, the resistive element constituting the RC filter reduces the adverse effect of the capacitance of the switch circuit on the second buffer circuit, thereby reducing the risk of an increase in noise components in the second clock signal and a deterioration in the duty ratio.

[0153] In addition, according to this circuit device, there is no need to provide resistive and capacitive elements that constitute an RC filter outside the circuit device in order to calculate the duty ratio of the first clock signal, thereby reducing the cost required to build an inspection system.

[0154] One aspect of the circuit device is The amplifier may include an RC filter electrically connected between the first node and the first terminal.

[0155] In this circuit device, the first node and the first terminal are electrically connected via an RC filter, so that the voltage of the first terminal is a DC voltage obtained by smoothing the first clock signal by the RC filter. Therefore, the external device can, for example, calculate the duty ratio of the first clock signal with high accuracy based on the voltage of the first terminal, and further calculate the duty ratio of the second clock signal with high accuracy based on the relationship between the duty ratio of the first clock signal and the duty ratio of the second clock signal.

[0156] Furthermore, according to this circuit device, the first terminal is used as a dedicated terminal for outputting a signal based on the first clock signal to the outside, thereby reducing the risk of the signal based on the first clock signal propagating to a circuit electrically connected to a terminal other than the first terminal and adversely affecting the circuit, thereby causing the circuit device to malfunction.

[0157] In addition, according to this circuit device, there is no need to provide resistive and capacitive elements that constitute an RC filter outside the circuit device in order to calculate the duty ratio of the first clock signal, thereby reducing the cost required to build an inspection system.

[0158] One aspect of the circuit device is a third buffer circuit electrically connected between an output node of the oscillation circuit and the first buffer circuit; The first buffer circuit may have a higher driving capability than the third buffer circuit.

[0159] According to this circuit device, since the first buffer circuit has a higher driving capability than the third buffer circuit, the first clock signal has a shorter rise time and fall time than the signal output from the third buffer circuit. Therefore, the first clock signal has a higher linearity in the relationship between the duty ratio and the DC bias than the signal output from the third buffer circuit. Therefore, the external device can calculate the duty ratio of the first clock signal with high accuracy from the signal based on the first clock signal output from the first terminal to the outside, and further calculate the duty ratio of the second clock signal with high accuracy based on the relationship between the duty ratio of the first clock signal and the duty ratio of the second clock signal.

[0160] In one aspect of the circuit device, The first node may be an input node of the second buffer circuit.

[0161] According to this circuit device, since the first node is close to the output node of the second buffer circuit, the difference between the duty ratio of the first clock signal and the duty ratio of the second clock signal is small, and therefore the external device can accurately calculate the duty ratio of the second clock signal based on the duty ratio of the first clock signal.

[0162] One embodiment of the oscillator is One aspect of the circuit device; and a vibrator. [Explanation of symbols]

[0163] 1...oscillator, 2...circuit device, 3...vibrator, 3a...excitation electrode, 3b...excitation electrode, 4...package, 5...lid, 6...external terminal, 7...accommodation chamber, 10...oscillator circuit, 11...reference voltage circuit, 12...bias current generating circuit, 13...capacitance circuit, 14...capacitance circuit, 15...variable capacitance circuit, 16...variable capacitance circuit, 17...variable capacitance circuit, 18...variable capacitance circuit, 20...output circuit, 21...wave shaping circuit, 22...frequency divider circuit, 23...pre-buffer, 24...output buffer, 25...pre-buffer, 26...output Output buffer, 30...temperature sensor, 32...temperature compensation circuit, 34...frequency control circuit, 36...logic circuit, 40...power supply circuit, 50...memory circuit, 51...register, 52...non-volatile memory, 60...RC filter, 61...resistance element, 62...capacitance element, 63...resistance element, 70...switch circuit, 71...transmission gate, 72...MOS transistor, 80...switch circuit, 81...transmission gate, 90...switch circuit, 101...bipolar transistor, 102...resistance element, 103...capacitance element, 104...capacitance element, 111...resistance element, 112...duty ratio adjustment circuit, 121...MOS transistor, 122...MOS transistor, 123...constant current source, 131-1 to 131-k...capacitance elements, 132-1 to 132-k...switching elements, 141-1 to 141-k...capacitance elements, 142-1 to 142-k...switching elements, 151...capacitance elements, 152-1 to 152-n...variable capacitance elements, 153-1 to 153-n...capacitance elements, 154...resistance element resistor element, 161...capacitance element, 162-1 to 162-n...variable capacitance elements, 163-1 to 163-n...capacitance elements, 164...resistance element, 171...capacitance element, 172-1 to 172-m...variable capacitance elements, 173-1 to 173-m...capacitance elements, 174...resistance element, 181...capacitance element, 182-1 to 182-m...variable capacitance elements, 183-1 to 183-m...capacitance elements, 184...resistance element, 211...buffer circuit, 251...buffer circuit, 252...buffer circuit, 261...buffer circuit

Claims

1. an oscillator circuit for generating an oscillation signal; a first buffer circuit that outputs a first clock signal based on the oscillation signal; a second buffer circuit that outputs a second clock signal based on the first clock signal; a first terminal electrically connectable to a first node at which the first buffer circuit outputs the first clock signal and configured to output the first clock signal to an external device; a second terminal electrically connected to a second node at which the second buffer circuit outputs the second clock signal; The oscillation circuit changes the oscillation signal based on duty ratio adjustment data calculated by an external device, a rise time of the first clock signal is shorter than a rise time of the second clock signal; a duty ratio of the second clock signal is calculated based on a correlation between the duty ratio of the first clock signal calculated by the external device and the duty ratio of the first clock signal and the duty ratio of the second clock signal; The duty ratio adjustment data is calculated based on a duty ratio of the second clock signal. A circuit device comprising:

2. The circuit device according to claim 1 , further comprising a switch circuit that electrically connects or disconnects the first node and the first terminal.

3. The circuit device according to claim 2 , further comprising a resistive element electrically connected between the first node and the switch circuit.

4. The circuit device of claim 2 , further comprising an RC filter electrically connected between the first node and the switch circuit.

5. The circuit device of claim 1 , further comprising an RC filter electrically connected between the first node and the first terminal.

6. a third buffer circuit electrically connected between an output node of the oscillation circuit and the first buffer circuit; The circuit device according to claim 1 , wherein the first buffer circuit has a higher driving capability than the third buffer circuit.

7. The circuit device according to claim 1 , wherein the first node is an input node of the second buffer circuit.

8. A circuit arrangement according to any one of claims 1 to 7; An oscillator comprising:

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