Reference current generating circuit and related calibration method

Abstract

The invention discloses a reference current generating circuit and a related calibration method. The reference current generation circuit comprises a temperature detection circuit, an adjustable resistor, a current mirror and a calibration circuit. The temperature detection circuit is used for detecting the temperature of the reference current generation circuit so as to provide voltage; the adjustable resistor is used for generating reference current according to the voltage; the current mirror is used for generating an output current according to the reference current. The calibration circuit comprises a resistor, a comparator and a control circuit. The resistor is used for generating an output voltage according to the output current; the comparator is used for comparing the output voltage with a reference voltage to generate a comparison result; and the control circuit is used for sequentially generating a plurality of control signals to the adjustable resistor and determining a final control signal according to the comparison result.

Description

Technical Field

[0001] The present invention relates to a reference current generation circuit, and more particularly to a reference current generation circuit with an automatic calibration mechanism. Background Art

[0002] In order to enable the reference current generation circuit in an integrated circuit to generate a reference current less affected by temperature, it is necessary to calibrate the reference current generation circuit to determine its parameters. If current correction is required, the traditional method is to provide an output pad on the chip and externally connect a resistor for measurement. However, fabricating an additional output pad on the chip increases the manufacturing cost and packaging difficulty. In addition, since the current reference is getting smaller currently, the relevant test equipment has a higher accuracy requirement, thus increasing additional costs. Summary of the Invention

[0003] Therefore, one object of the present invention is to provide a reference current generation circuit having an automatic calibration mechanism to complete the calibration of the reference current without the need for an external test equipment, so as to solve the problems described in the background art.

[0004] In an embodiment of the present invention, a reference current generation circuit is disclosed, which includes a temperature detection circuit, a variable resistor, a current mirror, and a calibration circuit. The temperature detection circuit is used to detect the temperature of the reference current generation circuit to provide a voltage; the variable resistor is used to generate a reference current according to the voltage; the current mirror is used to generate an output current according to the reference current. The calibration circuit includes a resistor, a comparator, and a control circuit. The resistor is used to generate an output voltage according to the output current; the comparator is used to compare the output voltage with a reference voltage to generate a comparison result; and the control circuit is used to sequentially generate a plurality of control signals to the variable resistor and determine the optimal resistance value of the variable resistor and the corresponding final control signal according to the comparison result.

[0005] In an embodiment of the present invention, a calibration method for a reference current generation circuit is disclosed, where the reference current generation circuit includes a temperature detection circuit, a variable resistor, and a current mirror. The temperature detection circuit is used to detect the temperature of the reference current generation circuit to provide a voltage; the variable resistor is used to generate a reference current according to the voltage; the current mirror is used to generate an output current according to the reference current. The calibration method includes the following steps: generating an output voltage according to the output current; comparing the output voltage with a reference voltage to generate a comparison result; and sequentially generating a plurality of control signals to the variable resistor and determining the optimal resistance value of the variable resistor and the corresponding final control signal according to the comparison result. Brief Description of the Drawings

[0006] Figure 1 Schematic diagram of a reference current generation circuit according to an embodiment of the present invention.

[0007] Figure 2 Schematic diagram of the resistance values of the reference current and the adjustable resistor before and after calibration.

[0008] Figure 3 Schematic diagram of a control circuit according to an embodiment of the present invention.

[0009] Figure 4 Flowchart of a calibration method for a reference current generation circuit according to an embodiment of the present invention. Detailed implementation manners

[0010] Figure 1 Schematic diagram of a reference current generation circuit 100 according to an embodiment of the present invention. As Figure 1 shown, the reference current generation circuit 100 includes a current mirror 110, a temperature detection circuit 120, an adjustable resistor 130, and a calibration circuit 140. In this embodiment, the temperature detection circuit 120 is used to detect the temperature of the reference current generation circuit 100 to provide a voltage V1 to the adjustable resistor 130, and the reference current Iref can be determined according to the voltage V1 and the resistance value of the adjustable resistor 130. The current mirror 110 is used to generate an output current Iref' according to the reference current Iref. In addition, in order to make the reference current Iref have a stable and correct value, the calibration circuit 140 included in the reference current generation circuit 100 can automatically calibrate the resistance value of the adjustable resistor 130. For example, when the chip or electronic device to which the reference current generation circuit 100 belongs is powered on, the calibration circuit 140 automatically performs calibration to determine the appropriate resistance value of the adjustable resistor 130. In this embodiment, all components of the reference current generation circuit 100 can be fabricated on a single chip, and no external components or test platforms are required during the process of the calibration circuit calibrating the resistance value of the adjustable resistor 130. Therefore, the manufacturing and testing costs of the chip to which the reference current generation circuit 100 belongs can be reduced.

[0011] In Figure 1 the reference current generation circuit 100, the current mirror 110 includes transistors M1, M2, and M3. Among them, the transistors M1, M2, and M3 are implemented by P-type metal-oxide-semiconductor field-effect transistors, but the present invention is not limited thereto. The transistors M1, M2, and M3 each include a first terminal, a second terminal, and a control terminal. The first terminals of the transistors M1, M2, and M3 are all connected to the supply voltage VDD. The control terminals of the transistors M1, M2, and M3 are connected to each other. The control terminal of the transistor M2 is connected to the second terminal, and the transistor M3 generates an output current Iref' according to the mirrored reference current Iref flowing through the transistor M2.

[0012] The temperature detection circuit 120 includes transistors M4 and M5. Among them, transistor M4 is implemented by an NPN bipolar transistor, and transistor M5 is implemented by an N-type metal-oxide-semiconductor field-effect transistor, but the present invention is not limited thereto. Transistor M4 includes a first terminal, a second terminal, and a control terminal. The first terminal of transistor M4 is connected to the second terminal of transistor M1 of the current mirror 110, and the second terminal is connected to the ground voltage. Transistor M5 includes a first terminal, a second terminal, and a control terminal. The first terminal of transistor M5 is connected to the second terminal of transistor M2 of the current mirror 110, the second terminal is connected to the adjustable resistor 130, and the control terminal of transistor M5 is connected to the control terminal of transistor M4.

[0013] It should be noted that Figure 1 The shown temperature detection circuit 120 is only for illustrative purposes and not a limitation of the present invention. In another embodiment, transistor M4 can be removed or replaced with a resistive element, and / or transistor M5 can be replaced with a bipolar transistor. These design changes should fall within the scope of the present invention.

[0014] The adjustable resistor 130 includes a plurality of serially connected transistors M6 - M10 and a plurality of serially connected resistors R1 - R5. Among them, transistors M6 - M10 are respectively connected to the plurality of resistors R1 - R5 in parallel. During the operation of the adjustable resistor, the on / off of transistors M6 - M10 can be controlled by a plurality of signals to determine the resistance value of the adjustable resistor 130. It should be noted that Figure 1 The shown adjustable resistor 130 is only for illustrative purposes and not a limitation of the present invention. In other embodiments, the number of transistors and resistors in the adjustable resistor 130 can vary according to the designer's consideration, and the connection manner of the transistors and resistors can also change.

[0015] The calibration circuit 140 includes a resistor RPP, a comparator 142, and a control circuit 144. The resistor RPP is coupled between the second terminal of transistor M3 and the ground voltage and is used to generate an output voltage VT according to the output current Iref'. The comparator 142 is used to compare the output voltage VT with a reference voltage Vref to generate a comparison result CR. The control circuit 144 can be a digital control circuit, which is used to sequentially generate a plurality of different control signals Vc to the adjustable resistor 130 (to control the resistance value of the adjustable resistor 130) and determine the optimal resistance value of the adjustable resistor 130 and its corresponding final control signal according to the comparison result CR. In one embodiment, the control signal Vc is a digital code, which can be used as a plurality of signals to control the on / off of transistors M6 - M10 or to generate the plurality of signals to control the on / off of transistors M6 - M10.

[0016] Specifically, when the reference current generation circuit 100 operates in the calibration mode, the control circuit 144 sequentially generates a plurality of different control signals Vc to the adjustable resistor 130, so that the resistance value of the adjustable resistor 130 increases from low to high. For example, the control circuit 144 sequentially generates a plurality of different control signals Vc with different digital codes to control the resistance value of the adjustable resistor 130 to increase sequentially from the lowest resistance value to the highest resistance value. As the resistance value of the adjustable resistor 130 increases sequentially, the reference current Iref and the output current Iref’ also decrease sequentially, thereby causing the voltage level of the output voltage VT to decrease sequentially. Since the output voltage VT is initially at a high voltage level, when the output voltage VT is higher than the reference voltage Vref, the comparison result CR output by the comparator 142 corresponds to the first logic value (e.g., "1"). As the voltage level of the output voltage VT decreases sequentially, once the output voltage VT is lower than the reference voltage Vref and the comparison result CR output by the comparator 142 corresponds to the second logic value (e.g., "0"), the control circuit 144 immediately records the control signal Vc at this time, for example, records the digital code corresponding to the control signal Vc at this time, as the final control signal. Briefly, the control circuit 144 sequentially generates a plurality of control signals Vc to control the resistance value of the adjustable resistor 130 to increase sequentially from the lowest resistance value to the highest resistance value, and if the comparison result CR switches from the first logic value to the second logic value, or from the second logic value to the first logic value, the control circuit 144 records the control signal Vc at this time as the final control signal. Through the final control signal, the adjustable resistor 130 will have an optimal resistance value so that the reference current Iref has an appropriate magnitude. Then, the reference current generation circuit 100 stops operating in the calibration mode.

[0017] In another embodiment, the control circuit 144 sequentially generates a plurality of different control signals Vc with different digital codes to control the resistance value of the adjustable resistor 130 to sequentially decrease from the highest resistance value to the lowest resistance value. As the resistance value of the adjustable resistor 130 sequentially decreases, the reference current Iref and the output current Iref' also sequentially increase, thereby causing the voltage level of the output voltage VT to sequentially increase. Since the output voltage VT is initially at a low voltage level, in the case where the output voltage VT is lower than the reference voltage Vref, the comparison result CR output by the comparator 142 corresponds to a second logic value (for example, "0"), and as the voltage level of the output voltage VT sequentially increases, once the output voltage VT is higher than the reference voltage Vref such that the comparison result CR output by the comparator 142 corresponds to a first logic value (for example, "1"), the control circuit 144 immediately records the control signal Vc at this time, for example, records the digital code corresponding to the control signal Vc at this time, as the final control signal. Simply put, the control circuit 144 sequentially generates a plurality of control signals Vc to control the resistance value of the adjustable resistor 130 to sequentially decrease from the highest resistance value to the lowest resistance value, and if the comparison result CR switches from the first logic value to the second logic value, or from the second logic value to the first logic value, the control circuit 144 records the control signal Vc at this time as the final control signal.

[0018] In addition, the above calibration mode can not only make the reference current Iref have an appropriate magnitude, but also synchronously calibrate the temperature curve of the reference current Iref. Specifically, the designer can make the resistance value of the adjustable resistor 130 have the same or similar temperature curve as the voltage V1 by configuring an appropriate reference voltage Vref. Figure 2 For example, before calibration, the temperature curve of the resistance value of the adjustable resistor 130 is inconsistent (not parallel) with the temperature curve of the voltage V1, so the reference current Iref has different values at different temperatures. After passing through the calibration mechanism of this embodiment, the temperature curve of the resistance value of the adjustable resistor 130 will be close to parallel with the temperature curve of the voltage V1, so the reference current Iref will not change significantly due to temperature changes.

[0019] In one embodiment, the control circuit 144 can be a digital control circuit, and the control circuit 144 records the final control signal in a non-volatile memory, that is, the reference current generation circuit 100 only needs to work in the calibration mode once.

[0020] In Figure 3In another embodiment shown, the control circuit 144 may include a flip-flop 310 and a decoder 320. In an example, the flip-flop 310 may be a D-type flip-flop, and the decoder 320 may be a 5-to-32 decoder. In the operation of the control circuit 144, the flip-flop 310 sequentially generates a plurality of different digital codes according to the clock signal CLK to the decoder 320, and the decoder generates a plurality of different control signals Vc to the adjustable resistor 130 according to the received digital codes. When the comparison result CR generated by the comparator 142 changes state, that is, when switching from the first logical value to the second logical value or from the second logical value to the first logical value, the flip-flop 310 locks, and the control signal Vc at this time is used as the final control signal. Since Figure 3 the control circuit 144 shown is implemented by the flip-flop 310 and the decoder 320, the control circuit 144 of the calibration circuit 140 operates in the calibration mode every time the reference current generation circuit 100 is powered on to determine the optimal resistance value of the adjustable resistor 130 and its corresponding final control signal.

[0021] Figure 4 FIG. 6 is a flowchart of a calibration method for the reference current generation circuit 100 according to an embodiment of the present invention. Referring to the content described in the above embodiments, the flow of the calibration method is as follows.

[0022] Step 400: Provide a reference current generation circuit, where the reference current generation circuit includes a temperature detection circuit, an adjustable resistor, and a current mirror. The temperature detection circuit is used to detect the temperature of the reference current generation circuit to provide a voltage; the adjustable resistor is used to generate a reference current according to the voltage; the current mirror is used to generate an output current according to the reference current.

[0023] Step 402: Generate an output voltage according to the output current.

[0024] Step 404: Compare the output voltage with a reference voltage to generate a comparison result.

[0025] Step 406: Sequentially generate a plurality of control signals to the adjustable resistor, and determine the optimal resistance value of the adjustable resistor and its corresponding final control signal according to the comparison result.

[0026] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

[0027] Description of Reference Numerals

[0028] 100: Reference current generation circuit

[0029] 110: Current mirror

[0030] 120: Temperature detection circuit

[0031] 130: Adjustable resistor

[0032] 140: Calibration circuit

[0033] 142: Comparator

[0034] 144: Control circuit

[0035] 310: Flip-flop

[0036] 320: Decoder

[0037] CLK: Clock signal

[0038] CR: Comparison result

[0039] Iref: Reference current

[0040] Iref’: Output current

[0041] M1-M10: Transistor

[0042] R1-R5: Resistor

[0043] RPP: Resistor

[0044] V1: Voltage

[0045] Vc: Control signal

[0046] Vref: Reference voltage

[0047] VT: Output voltage

Claims

1. A reference current generation circuit, comprising: A temperature detection circuit for detecting the temperature of the reference current generation circuit to provide a voltage; A variable resistor coupled to the temperature detection circuit for generating a reference current according to the voltage; A current mirror for generating an output current according to the reference current; And A calibration circuit, comprising: A resistor for generating an output voltage according to the output current; A comparator for comparing the output voltage with a reference voltage to generate a comparison result; And A control circuit for sequentially generating a plurality of control signals to the variable resistor and determining the optimal resistance value of the variable resistor and its corresponding final control signal according to the comparison result.

2. The reference current generation circuit according to claim 1, wherein the control circuit sequentially generates the plurality of control signals to control the resistance value of the variable resistor to sequentially increase from the lowest resistance value to the highest resistance value; and if the comparison result switches from a first logic value to a second logic value, or from the second logic value to the first logic value, the control circuit records the control signal at this time as the final control signal.

3. The reference current generation circuit according to claim 1, wherein the control circuit sequentially generates the plurality of control signals to control the resistance value of the variable resistor to sequentially decrease from the highest resistance value to the lowest resistance value; and if the comparison result switches from a first logic value to a second logic value, or from the second logic value to the first logic value, the control circuit records the control signal at this time as the final control signal.

4. The reference current generation circuit according to claim 1, wherein the control circuit is a digital control circuit, and the control circuit records the final control signal in a non-volatile memory.

5. The reference current generation circuit according to claim 1, wherein the control circuit comprises: A flip-flop for sequentially generating a plurality of digital codes according to a clock signal; and A decoder for sequentially receiving the plurality of digital codes and generating the plurality of control signals to the variable resistor according to the received plurality of digital codes.

6. The reference current generation circuit according to claim 5, wherein when the comparison result generated by the comparator changes state, the flip-flop uses the control signal at this time as the final control signal.

7. The reference current generation circuit according to claim 5, wherein the control circuit of the calibration circuit operates in a calibration mode every time the reference current generation circuit is powered on to determine the optimal resistance value of the variable resistor and the final control signal.

8. The reference current generation circuit according to claim 1, wherein the temperature detection circuit comprises a first transistor, the first transistor comprising a first terminal, a second terminal and a control terminal, the first terminal being coupled to the current mirror, and the second terminal being coupled to the variable resistor.

9. The reference current generating circuit according to claim 7, wherein the temperature detection circuit further includes a second transistor, the second transistor includes a first terminal, a second terminal and a control terminal, the first terminal of the second transistor is coupled to the current mirror, the second terminal of the second transistor is coupled to a ground voltage, and the control terminal of the second transistor is coupled to the control terminal of the first transistor.

10. A calibration method for a reference current generating circuit, wherein the reference current generating circuit includes: a temperature detection circuit for detecting the temperature of the reference current generating circuit to provide a voltage; a variable resistor coupled to the temperature detection circuit for generating a reference current according to the voltage; a current mirror for generating an output current according to the reference current; and the calibration method includes: generating an output voltage according to the output current; comparing the output voltage with a reference voltage to generate a comparison result; and sequentially generating a plurality of control signals to the variable resistor and determining the optimal resistance value of the variable resistor and its corresponding final control signal according to the comparison result.

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