High-precision reference current source

Abstract

The utility model discloses a high-precision reference current source, which is characterized in that a control signal can be obtained through a temperature signal generated by a digital output type temperature sensor and a data table stored in a nonvolatile memory, and the control signal can be converted into a pulse density signal through a sigma delta DA converter; a pulse density signal generates a group of non-overlapping clocks through the non-overlapping signal generation circuit to control the on-off of a group of differential MOS transistors M1 and M2 so as to control the equivalent resistance of the resistor R3 and further control the voltage of the VM, and the voltage of the VM is input to the positive end of the amplifier after being filtered. The amplifier and the MOS tube M3 form a structure similar to an LDO current source, the temperature coefficient of the resistor is counteracted by using a temperature-related signal, a current signal with a very small temperature coefficient is output, a wide temperature range can be considered, and high precision can be realized.

Description

Technical Field

[0001] The utility model relates to the technical field of high-precision reference sources, and particularly relates to a high-precision reference current source. Background Art

[0002] The high-precision reference current source is a key circuit inside many high-precision analog and mixed-signal chips. The design of existing such circuits relies on special processes and special equipment, such as calibration of such chips at the factory by methods such as laser trimming, with a high cost; at the same time, existing reference sources require means such as non-linear compensation and high-order compensation, and it is very difficult to balance requirements such as a wide temperature range, low power consumption, high precision, and high power supply voltage rejection ratio from the system structure; due to the non-linearity of the temperature characteristics of resistors and bipolar transistors themselves, it is very difficult to balance a wide temperature range (-40°C to 125°C) and high precision. The current solutions in the academic community are to use a pre-modulation circuit to generate a stable voltage to supply power to the subsequent stage, or to use a zener diode to stabilize at a potential to supply power to the subsequent stage, or to use a negative feedback adjustment circuit to adaptively adjust the accuracy of the output voltage. However, in the case of large fluctuations in the power supply voltage, this structure will cause relatively large changes in the output of the pre-modulation, resulting in poor linear regulation rate and low output accuracy of the overall circuit.

[0003] Therefore, the existing technology still needs to be improved. Summary of the Invention

[0004] In view of the deficiencies of the above-mentioned existing technology, the purpose of the utility model is to provide a high-precision reference current source, aiming to solve the problem that it is difficult for the existing reference source to balance a wide temperature range and low power consumption.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A high-precision reference current source, comprising:

[0007] A digital conversion circuit, on which there are a plurality of input terminals;

[0008] A digital output type temperature sensor, connected to one of the input terminals of the digital conversion circuit;

[0009] A non-volatile memory, connected to one of the input terminals of the digital conversion circuit;

[0010] A ΣΔ DA converter, connected to the output terminal of the digital conversion circuit, and outputting a pulse density signal to a non-overlapping signal generation circuit;

[0011] A resistor R3, with a MOS transistor M1 and a MOS transistor M2 connected to both ends, and connected to the two-phase output terminals of the non-overlapping signal generation circuit through the MOS transistor M1 and the MOS transistor M2;

[0012] An RC filter circuit is connected in parallel to resistor R3;

[0013] An amplifier, with its positive terminal connected to the RC filter circuit and its output terminal connected to MOS transistor M3;

[0014] A reference voltage source is connected to the negative terminal of the discharge circuit through equivalent resistor R1 and is simultaneously connected to MOS transistors M1 and M2 through equivalent resistor R2.

[0015] Further, the RC filter circuit includes capacitor C1, capacitor C2, and resistor R4, and capacitor C1 and capacitor C2 are connected in parallel to resistor R4.

[0016] Further, a CPU interface C is provided on the digital conversion circuit, and trimming data can be written through the CPU.

[0017] The technical solution adopted by the present utility model has the following beneficial effects:

[0018] In this application, first, a control signal can be obtained from the temperature signal generated by the digital output type temperature sensor and the data table stored in the non-volatile memory. The control signal can be converted into a pulse density signal through a ΣΔ DA converter. The pulse density signal generates a group of non-overlapping clocks through a non-overlapping signal generation circuit to control the on and off of a group of differential MOS transistors M1 and M2, thereby controlling the equivalent resistance of resistor R3 and further controlling the voltage of VM. The voltage of VM is filtered and then input to the positive terminal of the amplifier. The amplifier and MOS transistor M3 form a structure similar to an LDO current source, using the temperature-related signal to offset the temperature coefficient of the resistor, and outputting a current signal with a very small temperature coefficient, which can take into account a wide temperature range and reduce power consumption. Description of the Drawings

[0019] Figure 1 It is a schematic circuit diagram of a high-precision reference current source provided by the present utility model. Detailed Embodiments

[0020] To make the purpose, technical solution, and effects of the present utility model clearer and more definite, the following further elaborates on the present utility model with reference to the accompanying drawings and by way of examples. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0021] The high-precision current source includes a digital-output temperature sensor that can output an n-bit digital code according to the temperature and input it into a digital conversion circuit; a non-volatile memory, and the memory types include EEPROM, FLASH, and PROM implemented based on fuses or anti-fuses, etc.; a digital conversion circuit that can implement functions such as calling the netlist in the non-volatile memory, writing trimming data through the CPU, and outputting a control signal X; a ΣΔDA converter that converts the control signal into a pulse density signal linearly proportional to its duty cycle; a reference voltage source that generates a reference voltage with a very small temperature coefficient and is used for the bias of MOS transistors and the input of the amplifier in the negative feedback state; a non-overlapping signal generation circuit that generates two-phase non-overlapping clocks to control the turning on and off of MOS transistor M1 and MOS transistor M2, and an RC filter circuit that filters out the interference signals and irrelevant noise signals generated by turning on and off MOS transistor M1 and MOS transistor M2 due to the clock.

[0022] In this embodiment, during use, first, a control signal can be obtained through the temperature signal generated by the temperature sensor and the data table stored in the non-volatile memory. The control signal can be converted into a pulse density signal through the Sigma-Delta AD converter. The pulse density signal generates a group of non-overlapping clocks through the non-overlapping signal generation circuit to control the turning on and off of a group of differential MOS transistors M1 and MOS transistor M2, thereby controlling the equivalent resistance of R3 and further controlling the voltage of VM. The voltage of VM is filtered and then input to the positive terminal of the amplifier. The amplifier and MOS transistor M3 form a structure similar to an LDO current source, and the temperature-related signal is used to cancel the temperature coefficient of the resistor, and a current signal with a very small temperature coefficient is output.

[0023] Before the chip leaves the factory, the chip can be trimmed through the CPU interface, and the trimming parameters are written into the non-volatile memory. When the chip is powered on later, first, data is read from the non-volatile memory, and through the arithmetic circuit in the data conversion module, the conversion from the temperature signal T to the control signal X is accurately realized, and finally, the accurate output current IL is obtained.

[0024] An on-chip temperature sensor is used in the current source circuit, which can output an n-bit digital signal T that is proportional to the chip temperature in real time.

[0025] An m-bit control signal X can be obtained by using the temperature signal T and the data table stored in the non-volatile memory. Figure 1 The non-volatile memory in can be inside the chip or outside the chip, and the memory types include EEPROM, FLASH, and PROM implemented based on fuses or anti-fuses, etc.

[0026] The control signal X is converted into a pulse density signal Z through the ΣΔDA circuit, and the average duty cycle of the pulse density signal Z is linearly related to the control signal X;

[0027] The pulse density signal Z is converted into Q and QN through a two-phase non-overlapping circuit, which respectively control the P-type MOS transistor M1 and the MOS transistor M2. The logic values of Q and QN are opposite when stable, and there will be no state where both are high during the conversion stage.

[0028] Figure 1 The reference voltage source in it can generate a reference voltage VR with a very low temperature coefficient and has a certain load-carrying capacity. The equivalent resistance R2 and the resistor R3 are of the same type of resistor. Changing the duty cycle of the pulse density signal Z is equivalent to adjusting the resistor R3. Therefore, the average voltage of the VM point can be determined by the average duty cycle of the pulse density signal Z, and the voltage at the non-inverting input terminal V+ of the amplifier A1 can be accurately adjusted after filtering. Figure 1 The filter capacitors C1 and C2 in it can be inside the chip or outside the chip.

[0029] Figure 1 The amplifier A1 in it is a high-gain amplifier, which operates in a negative feedback state. The voltage V- at its inverting input terminal is equal to the voltage at the non-inverting input terminal, and the output current IL = (VR - V-) / R1. When the relationship between the voltage at the V- point and temperature change can offset the influence of the temperature coefficient of R1, a reference current IL that is basically independent of temperature can be obtained.

[0030] Before leaving the factory, the chip can be trimmed through the Figure 1 CPU interface in it, and the trimming parameters are written into the non-volatile memory. When the chip is powered on later, it first reads data from the non-volatile memory, and through the arithmetic circuit in the data conversion module, the conversion from the temperature signal T to the control signal X is accurately realized. Finally, through the adjustment of the load resistor RL, an accurate output current IL is obtained.

[0031] The technical solution adopted by the present utility model has the following beneficial effects:

[0032] (1) In the current source design, a digital output type temperature sensor is used to measure the chip temperature in real time;

[0033] (2) In the current source design, a digital output type temperature sensor, a non-volatile memory, a digital conversion circuit, a ΣΔ DA converter, a non-overlapping signal generation circuit and an RC filter circuit are used to generate a voltage with specific temperature characteristics;

[0034] (3) In the current source design, a reference voltage source, a high-gain amplifier A1 and devices such as resistors and MOS transistors are used, and according to the Figure 1 connection method shown, a specific voltage is converted into a current.

[0035] Other embodiments of the present utility model will be readily conceived by those skilled in the art after considering the specification and practicing the solutions disclosed herein. The present utility model is intended to cover any variations, uses, or adaptations of the present utility model, which follow the general principles of the present utility model and include well-known general knowledge or conventional technical means in the technical field not disclosed in this disclosure. The specification and examples are only regarded as exemplary, and the true scope and spirit of the present utility model are pointed out by the claims.

Claims

1. A high-precision reference current source, characterized in that: include: A digital conversion circuit, wherein the digital conversion circuit is provided with a plurality of input terminals; A digital output temperature sensor connected to one of the input terminals of the digital conversion circuit; a nonvolatile memory connected to one of the input terminals of the digital conversion circuit; a ΣΔDA converter connected to the output end of the digital conversion circuit and outputting a pulse density signal to a non-overlapping signal generating circuit; The resistor R3 has two ends connected with the MOS transistor M1 and the MOS transistor M2, and is connected to the two-phase output ends of the non-overlapping signal generating circuit through the MOS transistor M1 and the MOS transistor M2; RC filter circuit, connected in parallel with resistor R3; Amplifier, the positive end is connected to the RC filter circuit, and the output end is connected to the MOS tube M3; The reference voltage source is connected to the negative end of the discharger circuit through an equivalent resistor R1, and is simultaneously connected to the MOS tube M1 and the MOS tube M2 through an equivalent resistor R2.

2. The high-precision reference current source according to claim 1, characterized in that: The RC filter circuit includes a capacitor C1, a capacitor C2 and a resistor R4, and the capacitor C1 and the capacitor C2 are connected in parallel to the resistor R4.

3. The high-precision reference current source according to claim 1, characterized in that: The digital conversion circuit is provided with a CPU interface C, and the adjustment data can be written into the CPU.

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