Semiconductor device and crystal oscillator

Abstract

To reduce the number of external components in a semiconductor device having an oscillation circuit that oscillates a crystal oscillator.SOLUTION: A semiconductor device (1A) has at least one of a first inductor (101) and a second inductor (102), and at least one of the first inductor and the second inductor is composed of GIC circuits (GC1, GC2) configured to generate inductance by a combination of impedance elements.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor device. [Background technology]

[0002] Conventionally, a technique for oscillating a crystal resonator using an oscillation circuit is known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-141224 A

[0004] [overview] Here, in a semiconductor device having an integrated oscillator circuit, it is desirable to reduce as much as possible the number of external components that need to be connected to the outside of the semiconductor device.

[0005] In view of the above circumstances, an object of the present disclosure is to reduce the number of external components in a semiconductor device including an oscillation circuit that causes a crystal resonator to oscillate.

[0006] A semiconductor device according to an embodiment of the present disclosure includes: A semiconductor device having at least a part of an oscillation circuit for oscillating a crystal resonator integrated therein, The oscillator circuit includes: a load capacitance connected in series to the equivalent model of the crystal resonator; The crystal unit further includes at least one of a first inductor connected in series with the load capacitance and a frequency selection circuit including a first capacitor and a second inductor connected in parallel, the frequency selection circuit being configured to select an overtone order for overtone oscillation of the crystal unit; The semiconductor device includes at least one of the first inductor and the second inductor, At least one of the first inductor and the second inductor is formed by a GIC circuit configured to generate an inductance by a combination of impedance elements. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a configuration of a crystal oscillation device according to a first comparative example. [Diagram 2] FIG. 2 is a diagram showing an equivalent model of a quartz crystal unit. [Diagram 3] FIG. 3 is a diagram showing a configuration of a crystal oscillation device according to a second comparative example. [Figure 4] FIG. 4 shows an equivalent model of a quartz crystal unit with a load capacitance and an extension coil connected to it. [Diagram 5] FIG. 5 is a diagram showing a configuration of a crystal oscillation device according to a third comparative example. [Figure 6] FIG. 6 is a diagram showing the configuration of the crystal oscillation device according to the first embodiment. [Figure 7] FIG. 7 is a diagram showing a GIC circuit. [Figure 8] FIG. 8 is a diagram showing the configuration of a crystal oscillation device according to the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of the temperature characteristic of the oscillation frequency. [Figure 10] FIG. 10 is a diagram showing an example of a circuit that applies a bias to a GIC circuit.

[0008] [Detailed Description] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0009] <Comparative Example> Here, comparative examples to be compared with the embodiments of the present disclosure will be described. Fig. 1 is a diagram showing the configuration of a crystal oscillation device according to a first comparative example.

[0010] 1 includes a crystal oscillator X and an oscillation circuit 110. The oscillation circuit 110 is an amplifier circuit using a transistor Tr, which forms a loop in which the output of the crystal oscillator X is fed back to the input, thereby allowing the amplifier to continue amplifying the output.

[0011] Specifically, the oscillator circuit 110 is a so-called Colpitts type oscillator circuit, and includes resistors R11 to R13, capacitors C11 to C13, a variable capacitance Cv, and a transistor Tr. The transistor Tr is an NPN transistor. The base of the transistor Tr is connected to the output terminal of the crystal unit X. The collector of the transistor Tr is connected to the application terminal of the power supply voltage Vcc. The resistors R11 and R12 are connected in series between the application terminal of the power supply voltage Vcc and a ground terminal (application terminal of the ground potential). The node to which the resistors R11 and R12 are connected is connected to the base of the transistor Tr. The emitter of the transistor Tr is connected to the ground terminal via the resistor R13. The capacitors C11 and C12 are connected in series between the base of the transistor Tr and the ground terminal. The node to which the capacitors C11 and C12 are connected is connected to the emitter of the transistor Tr. The capacitor C13 and the variable capacitance Cv are connected in parallel between the input terminal of the crystal unit X and the ground terminal. An output signal OUT is outputted via a capacitor Co from a node where the emitter of the transistor Tr and the resistor R13 are connected.

[0012] Fig. 2 is a diagram showing an equivalent model of a quartz crystal unit X. In Fig. 2, an equivalent series resistance R1, a series inductance L1, and a series capacitance C1 are connected in series, and a parallel capacitance C0 is connected in parallel.

[0013] If the series resonance frequency is fr and the resonance frequency when the load capacitance CL is connected in series to the crystal unit X is fL, the following equation (1) is established.

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[0014] The load capacitance CL is expressed by the following equation (2) using the capacitors C11, C12, and C13 and the variable capacitance Cv.

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[0015] Therefore, by adjusting the value of the variable capacitance Cv in accordance with manufacturing variations in the crystal resonator X, the load capacitance CL can be adjusted, and the frequency (=fL) of the output signal OUT can be adjusted to a predetermined frequency.

[0016] When the load capacitance CL is variable from CL1 to CL2, the frequency variable range is given by the following formula (3).

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[0017] When using the oscillator circuit according to the first comparative example as described above, it is necessary to reduce the thickness of the crystal unit in order to obtain a high-frequency output signal. This is because the oscillation frequency of the crystal unit is inversely proportional to its thickness. However, reducing the thickness requires high processing accuracy.

[0018] The oscillation circuit of the first comparative example is a circuit for oscillating in a fundamental wave mode, but the crystal unit can be made to oscillate in an odd-number multiple order mode of the fundamental wave. An example of an oscillation circuit for performing such overtone oscillation is the oscillation circuit 120 shown in FIG.

[0019] The crystal oscillation device 12 according to the second comparative example shown in FIG. 3 includes a crystal resonator X and an oscillation circuit 120. The oscillation circuit 120 differs from the oscillation circuit 110 according to the first comparative example in that inductors La and Lb are added. The capacitors C11, Cx, and C12 are connected in series between the base of the transistor Tr and the ground terminal. The capacitor Cx is connected between the capacitors C11 and C12. The resistor R13 and the inductor La are connected in series between the emitter of the transistor Tr and the ground terminal. The capacitor Cx is connected across the resistor R13. The inductor La and the capacitor C12 are connected in parallel.

[0020] The inductor La and the capacitor C12 constitute a frequency selection circuit Fs. The frequency selection circuit Fs suppresses oscillation of the fundamental or lower order to ensure overtone oscillation. For example, the values ​​of La and C12 are set so that the parallel resonance frequency of La and C12 is midway between the frequency of the desired overtone order and the frequency of the lower overtone order or the frequency of the fundamental.

[0021] Furthermore, in the above formula (3), the series capacitance C1 of the crystal unit X is inversely proportional to the square of the overtone order and becomes smaller even if the thickness of the crystal unit X is the same. This reduces the frequency pull range. Therefore, in order to ensure the frequency pull range, an inductor Lb is added. The inductor Lb is also called an extension coil, and the load capacitance CL and the extension coil Lb are connected in series to the equivalent model of the crystal unit X as shown in Figure 4. In this case, the following formula (4) holds true.

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[0022] Overtone oscillation can be performed by the oscillator circuit 120 according to the second comparative example. However, when using a semiconductor device in which a part of the oscillator circuit 120 is integrated, the inductors La and Lb need to be configured as external discrete coil components with respect to the semiconductor device.

[0023] 5 is a diagram showing a configuration of a crystal oscillation device 13 according to a third comparative example. The crystal oscillation device 13 includes a crystal unit X and an oscillation circuit 130. The oscillation circuit 130 is a circuit capable of performing overtone oscillation.

[0024] The oscillation circuit 130 includes an inverter IV, a feedback resistor Rf, a limiting resistor Rd, a damping resistor Rb, capacitors Ca, Cb, and Cc, and inductors La and Lb. The output terminal of the inverter IV is connected to a first terminal of the limiting resistor Rd. The second terminal of the limiting resistor Rd is connected to an input terminal of the crystal unit X via a parallel connection configuration of the inductor Lb and the damping resistor Rb. The output terminal of the crystal unit X is connected to an input terminal of the inverter IV. A feedback resistor Rf is connected between the input and output terminals of the inverter IV. A capacitor Cc and a parallel connection configuration of the inductor La and the capacitor Ca are connected in series between the second terminal of the limiting resistor Rd and the ground terminal. The parallel connection of the inductor La and the capacitor Ca constitutes a frequency selection circuit Fs. A capacitor Cb is connected between the output terminal of the crystal unit X and the ground terminal.

[0025] With this configuration, the output of the crystal unit X is amplified by the amplifier circuit made up of the inverter IV and feedback resistor Rf and returned to the input, continuing the oscillation. The oscillated output signal OUT is taken out from the output terminal of the inverter IV.

[0026] A load capacitance consisting of capacitors Ca, Cb, and Cc is connected in series to the crystal unit X. As in the second comparative example, the frequency selection circuit Fs suppresses low-order mode oscillation and ensures oscillation at a desired overtone order. The oscillation frequency can be adjusted by adjusting the load capacitance. Also, an inductor Lb is provided to ensure a variable frequency range, as in the second comparative example.

[0027] In the configuration of the third comparative example, similarly to the second comparative example, when a semiconductor device in which part of the oscillator circuit 130 is integrated is used, the inductors La and Lb need to be configured as external coil components.

[0028] First Embodiment 6 is a diagram showing a configuration of a crystal oscillation device 1 according to a first embodiment of the present disclosure. The crystal oscillation device 1 includes a crystal resonator X and a semiconductor device 1A.

[0029] The semiconductor device 1A has an oscillator circuit 10, a resistor selection signal generating circuit 10A, and a non-volatile memory 10B integrated together. In the configuration of Fig. 6, the semiconductor device 1A has all the components of the oscillator circuit 10 integrated together, but it may have some of the components of the oscillator circuit 10 integrated together. For example, among the components shown in Fig. 6, the capacitors C12 and C13 may be external components of the semiconductor device 1A.

[0030] The oscillator circuit 10 is capable of overtone oscillation, and includes inductors 101 and 102 in addition to resistors R11 to R13, capacitors C11 to C13, a capacitor Cx, and a transistor Tr.

[0031] The oscillator circuit 10 according to this embodiment has a configuration that is contrasted with the second comparative example (FIG. 3), and does not include a variable capacitance Cv. Also, an inductor 101 is used instead of the inductor Lb. The inductor 101 is formed of a GIC (Generalized Impedance Converter) circuit GC1.

[0032] Here, the GIC circuit will be described with reference to FIG. 7. As shown in FIG. 7, the GIC circuit GC has impedance elements Z1 to Z5 and amplifiers AP1 and AP2. The impedance elements Z1 to Z5 are connected in series between a first end TH and a second end TL. The non-inverting input end of the amplifier AP1 is connected to the first end TH. The inverting input end of the amplifier AP1 is connected to the node to which the impedance elements Z2 and Z3 are connected. The output end of the amplifier AP1 is connected to the node to which the impedance elements Z3 and Z4 are connected. The inverting input end of the amplifier AP2 is connected to the node to which the impedance elements Z2 and Z3 are connected. The non-inverting input end of the amplifier AP2 is connected to the node to which the impedance elements Z4 and Z5 are connected. The output end of the amplifier AP2 is connected to the node to which the impedance elements Z1 and Z2 are connected.

[0033] In a GIC circuit, resistors or capacitors are used as impedance elements, and a desired impedance can be obtained by combining impedance elements. As shown in Figure 7, if impedance elements Z1 to Z3 and Z5 are resistors and Z4 is a capacitor, the following impedance Z is realized. Z=jωC4((R1R3R5) / R2) where R1, R2, R3, and R5 are the resistance values ​​of impedance elements Z1, Z2, Z3, and Z5, respectively, and C4 is the capacitance value of impedance element Z4.

[0034] 6, the inductor 101 is configured with a GIC circuit GC1, a first terminal TH of the GIC circuit GC1 is connected to the base of the transistor Tr, and a second terminal TL of the GIC circuit GC1 is connected to the output terminal of the crystal unit X.

[0035] Furthermore, the inductance value of the inductor 101 is made variable by making the resistance values ​​of the impedances Z1 to Z3 and Z5 (=resistors) of the GIC circuit GC1 variable. By making the inductance value of the inductor 101 variable, the oscillation frequency in the overtone oscillation can be adjusted, and the frequency variable range can be increased. A change in the inductance value of several μH is sufficient for frequency adjustment; for example, if the resistance values ​​of the impedance elements Z1 to Z3 and Z5 in the GIC circuit are all 1 kΩ, the capacitance value of the impedance element Z4 is 1 pF, and the inductance value is 1 μH, an inductance value of 4 μH can be easily obtained by setting the resistance value to 2 kΩ.

[0036] In this way, by making the resistance values ​​of the impedance elements Z1 to Z3 and Z5 variable at the same value R, the inductance value is C4·R 2 This makes it easy to understand the change in inductance value. However, the inductance values ​​Z1 to Z3 and Z5 may be independently variable, or the resistance value of any of the inductance values ​​Z1 to Z3 and Z5 may be fixed. Also, the capacitance value of the impedance element Z4 may be variable.

[0037] In this way, by configuring the inductor 101 using a GIC circuit, the inductor 101 can be configured on an integrated circuit in the semiconductor device 1A, and the number of external components can be reduced.

[0038] In this embodiment, in order to deal with manufacturing variations in the crystal unit X, the resistance values ​​of the impedance elements Z1 to Z3 and Z5 are adjusted so that the oscillation frequency becomes a desired frequency in a product shipping test. The adjustment result is stored in the non-volatile memory 10B as resistance value setting data. When the product is used, the resistance selection signal generation circuit 10A sets the resistance values ​​of the impedance elements Z1 to Z3 and Z5 based on the resistance value setting data read from the non-volatile memory 10B. For example, the resistance selection signal generation circuit 10A generates a resistance selection signal for selecting a resistor to be enabled by selecting which resistor to bypass among the resistors connected in series, thereby setting the resistance values ​​of the impedance elements Z1 to Z3 and Z5.

[0039] In addition, in the oscillator circuit 10, the inductor 102 and the capacitor C12 are connected in parallel to form a frequency selection circuit Fs. The frequency selection circuit Fs selects the order of overtone oscillation. The inductor 102 is formed of a GIC circuit GC2. A first terminal TH of the GIC circuit GC2 is connected to a resistor R13. A second terminal TL of the GIC circuit GC2 is connected to a ground terminal. In this way, by forming the inductor 102 from a GIC circuit, the inductor 102 can be formed on an integrated circuit in the semiconductor device 1A, and external components can be reduced.

[0040] It should be noted that the resistance value or capacitance value of the impedance element in inductor 102 may be made variable, thereby making the inductance value of inductor 102 variable and variably selecting the overtone order.

[0041] Moreover, the inductance value of the inductor 101 may be fixed, and the oscillation frequency may be adjusted, for example, by using a variable capacitance connected in parallel to the capacitor C13, as in the second comparative example.

[0042] <Second embodiment> 8 is a diagram showing a configuration of a crystal oscillation device 1X according to a second embodiment of the present disclosure. The crystal oscillation device 1X includes a crystal resonator X and a semiconductor device 1AX. The semiconductor device 1AX differs from the first embodiment in that it includes an integrated temperature sensor 10C.

[0043] Here, Fig. 9 is a diagram showing an example of the temperature characteristics of the oscillation frequency. The horizontal axis of Fig. 9 indicates temperature, and the vertical axis indicates the error when the oscillation frequency at room temperature T0 is set to 0. In Fig. 9, a solid line indicates a case where there is no error in the cut angle of the AT cut of the quartz crystal unit (cutting at an angle of "35°15'" from the Z axis of the quartz crystal), a dashed line indicates a case where there is a positive error in the cut angle, and a fine dashed line indicates a case where there is a negative error in the cut angle.

[0044] 9, the higher the temperature is from room temperature T0, the lower the oscillation frequency is, and the lower the temperature is from room temperature T0, the higher the oscillation frequency is. Also, the temperature characteristics change depending on the cut angle error of the AT cut.

[0045] As can be seen from the above formula (4), as the inductance value (corresponding to Lb in formula (4)) of inductor 102 increases, the oscillation frequency decreases, and as the inductance value decreases, the oscillation frequency increases. Assuming that the resistance values ​​of impedance elements Z1 to Z3 and Z5 are the same, in order to increase the inductance value, the resistance value is increased, and to decrease the inductance value, the resistance value is decreased. As a result, in consideration of the temperature characteristics shown in FIG. 9, if the resistance value is decreased to increase the oscillation frequency when the temperature is higher than room temperature T0, and the resistance value is increased to decrease the oscillation frequency when the temperature is lower than room temperature T0, the change in the oscillation frequency due to temperature can be suppressed.

[0046] Therefore, in this embodiment, correspondence information (such as a table) indicating the correspondence relationship between temperature and resistance value settings is stored in advance in the non-volatile memory 10B, and the resistance selection signal generation circuit 10A generates a resistance selection signal based on the temperature measured by the temperature sensor 10C and the above correspondence information, and sets the resistance values ​​of the impedance elements Z1 to Z3 and Z5 in the inductor 101. Here, if the above correspondence information is information corresponding to the cut angle error of the AR cut, the temperature characteristic of the oscillation frequency can be improved regardless of the cut angle error.

[0047] <About bias> When the outputs of the amplifiers AP1, AP2 in the GIC circuit become close to the power supply voltage of the amplifiers AP1, AP2 or close to the ground potential, the desired characteristics cannot be obtained. Therefore, for example, as shown in FIG. 10, it is desirable to connect the first end TH of the GIC circuit constituting the inductor 102 to the application end of the bias voltage Vbs via a resistor Rbs. This allows the outputs of the amplifiers AP1, AP2 to be biased to the midpoint between the power supply voltage and the ground potential. Note that FIG. 10 shows an example in which a GIC circuit is applied to the inductor La of the oscillator circuit 130 (FIG. 5) according to the third comparative example. Also, a GIC circuit may be applied to the inductor Lb.

[0048] <Other> In addition to the above-mentioned embodiment, various technical features disclosed in this specification can be modified in various ways without departing from the spirit of the technical creation. In other words, the above-mentioned embodiment should be considered to be illustrative and not restrictive in all respects, and the technical scope of the present invention should not be limited to the above-mentioned embodiment, but should be understood to include all modifications that fall within the meaning and scope equivalent to the scope of the claims.

[0049] <Additional Notes> As described above, the semiconductor device (1A) according to one embodiment of the present disclosure is a semiconductor device having, in an integrated form, at least a part of an oscillator circuit (1A) for oscillating a quartz crystal resonator (X), The oscillator circuit includes: A load capacitance (CL) is connected in series with the equivalent model of the crystal unit, The crystal unit further includes at least one of a first inductor (101) connected in series with the load capacitance, and a frequency selection circuit (Fs) configured to select an overtone order for overtone oscillation of the crystal unit and including a first capacitor (C12) and a second inductor (102) connected in parallel; The semiconductor device includes at least one of the first inductor and the second inductor, At least one of the first inductor and the second inductor is configured by a GIC circuit (GC1, GC2) configured to generate an inductance by a combination of impedance elements (first configuration).

[0050] In the first configuration, at least one of the impedance elements in the GIC circuit that constitutes the first inductor may have a variable resistance value or a variable capacitance value (second configuration).

[0051] In the second configuration, all of the resistance values ​​of the impedance elements may be set to the same variable value (third configuration).

[0052] In the second or third configuration, a non-volatile memory (10B); a setting control unit (10A) configured to set a resistance value or a capacitance value of the impedance element based on the setting value information stored in the non-volatile memory; It may further comprise the above (fourth configuration).

[0053] In the fourth configuration, the device further includes a temperature sensor (10C), The setting control unit may be configured to set the resistance value or capacitance value of the impedance element based on correspondence information representing the correspondence between the temperature stored in the non-volatile memory and the setting value information and the temperature measured by the temperature sensor (fifth configuration).

[0054] In addition, in any of the first to fifth configurations, at least one of the impedance elements in the GIC circuit (GC2) constituting the second inductor (102) may be configured to have a variable resistance value or capacitance value (sixth configuration).

[0055] In any of the first to sixth configurations, the first terminal of the GIC circuit may be configured to be connectable to an application terminal of a bias voltage (Vbs) via a resistor (Rbs) (seventh configuration).

[0056] A crystal oscillation device (1) according to an embodiment of the present disclosure includes a semiconductor device (1A) having any one of the first to seventh configurations described above, and the crystal resonator (X) (eighth configuration). [Industrial Applicability]

[0057] The present disclosure can be used in crystal oscillator devices for a variety of purposes. [Explanation of symbols]

[0058] 1. Crystal Oscillator 1A Semiconductor Device 1AX Semiconductor Device 1X Crystal Oscillator 10 Oscillator Circuit 10A Resistor Selection Signal Generation Circuit 10B non-volatile memory 10C Temperature Sensor 11, 12, 13 Crystal Oscillator 101,102 Inductors 110,120,130 Oscillator circuit AP1, AP2 amplifier C0 parallel capacitance C1 equivalent series capacitance C11, C12, C13 capacitors CL load capacity Ca capacitor Ca, Cb, Cc capacitors Co Capacitor Cv variable capacitance Fs Frequency selection circuit GC GIC circuit GC1,GC2 GIC circuit IV Inverter L1 Series inductance La,Lb Inductor R1 equivalent series resistance R11~R13 Resistors Rb Dump resistor Rbs Resistance Rd Limiting Resistor Rf Feedback resistor TH 1st end TL 2nd end Tr Transistor X Crystal Oscillator Z1~Z5 Impedance elements

Claims

1. A semiconductor device having at least a part of an oscillation circuit for oscillating a crystal resonator integrated therein, The oscillator circuit includes: a load capacitance connected in series to the equivalent model of the crystal resonator; The crystal unit further includes at least one of a first inductor connected in series with the load capacitance and a frequency selection circuit including a first capacitor and a second inductor connected in parallel, the frequency selection circuit being configured to select an overtone order for overtone oscillation of the crystal unit; The semiconductor device includes at least one of the first inductor and the second inductor, At least one of the first inductor and the second inductor is configured as a GIC circuit configured to generate inductance by a combination of impedance elements.

2. 2. The semiconductor device according to claim 1, wherein at least one of the impedance elements in the GIC circuit constituting the first inductor has a variable resistance value or a variable capacitance value.

3. 3. The semiconductor device according to claim 2, wherein all resistance values ​​of said impedance elements are set to the same value and are variable.

4. A non-volatile memory; a setting control unit configured to set a resistance value or a capacitance value of the impedance element based on the setting value information stored in the non-volatile memory; The semiconductor device according to claim 2 , further comprising:

5. Further comprising a temperature sensor; 5. The semiconductor device according to claim 4, wherein the setting control unit sets a resistance value or a capacitance value of the impedance element based on correspondence information representing a correspondence relationship between the temperature stored in the non-volatile memory and the setting value information and a temperature measured by the temperature sensor.

6. 2. The semiconductor device according to claim 1, wherein at least one of the impedance elements in the GIC circuit constituting the second inductor has a variable resistance value or a variable capacitance value.

7. The semiconductor device according to claim 1 , wherein the first terminal of the GIC circuit is connectable to a terminal to which a bias voltage is applied via a resistor.

8. A crystal oscillation device comprising: the semiconductor device according to claim 1; and the crystal resonator.

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