A constant temperature reference current source with zero temperature drift coefficient

Abstract

The present invention relates to a constant temperature reference current source with a zero temperature drift coefficient, characterized in that: it includes a bias voltage generating circuit and a zero temperature drift coefficient circuit; the voltage output end of the bias voltage generating circuit is provided with a plurality of switches, and a specific voltage is output by selecting a combination of closed switches, generating a specific voltage to be input into the zero temperature drift coefficient circuit, so that the MOS tube in the zero temperature drift coefficient circuit is turned on, and then a reference current with a zero temperature drift coefficient is generated. The present invention has a simple overall structure, does not require the use of components such as resistors, can avoid the decrease in accuracy caused by the temperature coefficient of the resistor, and reduces the cost; any specific V can be achieved by controlling the closing of the Vse switch bias Voltage is used to turn on the zero temperature drift coefficient circuit, thereby generating a reference current with a zero temperature drift coefficient; or a high-precision constant temperature reference current source for various currents can be achieved by selecting different MOS tube W / L ratios.

Description

Technical Field

[0001] The invention relates to the technical field of reference current sources, and in particular to a constant temperature reference current source with a zero temperature drift coefficient. Background Art

[0002] The reference current source is a very important module in the integrated circuit. It is used to provide a high-precision, low-temperature-coefficient current source for other circuits. The accuracy and temperature coefficient of the reference current largely determine the performance of the circuit.

[0003] There are three main existing methods to achieve a high-precision, low-temperature drift reference current source: one is to use off-chip devices, which will increase the cost of the system and have large discreteness; one is to use the ratio of the on-chip integrated reference voltage to the resistor, but the on-chip resistor generally has a temperature coefficient, and the area of ​​the resistor will also be large in ultra-low power consumption scenarios; one is to use the characteristics of the diode to generate a positive temperature coefficient and a negative temperature coefficient, and then superimpose these two currents in a certain ratio to generate a low-temperature drift reference current, such as Figure 1 As shown, a reference current source with a low temperature drift coefficient is generated by superimposing currents with a negative temperature coefficient and a positive temperature coefficient at a certain proportional coefficient. The forward voltage of the transistor (Q1) shows a negative temperature coefficient (V1) with temperature, and the base-emitter voltage difference of the two transistors (Q2, Q3) working at different current densities shows a positive temperature coefficient (V2-V3); therefore, the current V1 / R1 flowing through R1 under the action of operational amplifier feedback is a negative temperature coefficient current, and the current (V2-V3) / R2 flowing through R2 under the action of operational amplifier feedback is a positive temperature coefficient. A current source with a low temperature drift coefficient can be generated by superimposing a certain proportion K as shown in the formula; however, due to mismatch and process drift, in order to generate a reference current with a low temperature coefficient, additional tests need to be added to adjust the resistance value and the proportion K; due to the mismatch between periods and the drift of parameters during the manufacturing process, a lot of test costs need to be added to adjust the superimposed proportion. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a constant temperature reference current source with a zero temperature drift coefficient, thereby solving the problems existing in the prior art reference current source.

[0005] The object of the present invention is achieved by the following technical scheme: a constant temperature reference current source with zero temperature drift coefficient, which includes a bias voltage generating circuit and a zero temperature drift coefficient circuit; a voltage output end of the bias voltage generating circuit is provided with a plurality of switches, and a specific voltage is output by selecting a combination of closed switches, and a specific voltage is generated and input into the zero temperature drift coefficient circuit, so that the MOS tube in the zero temperature drift coefficient circuit is turned on, thereby generating a reference current with a zero temperature drift coefficient;

[0006] The specific voltage is calculated by: Then get Where Iref is the drain current of the MOS tube; μ n is the mobility of the MOS tube; C ox is the gate oxide capacitance of the MOS tube; W is the length of the MOS tube; L is the channel width of the MOS tube; Vref is the gate voltage of the MOS tube; V T is the threshold voltage of the MOS tube; Iref(T) is the drain current of the MOS tube expressed in temperature; a vt is the temperature coefficient of the threshold voltage; a u is the temperature coefficient of mobility.

[0007] The bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to a reference voltage source, and the output terminal of the comparator is connected in series with an R1n resistor string and an R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a Vse switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each Vse switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0008] The zero temperature drift coefficient circuit includes a plurality of parallel MOSFET combinations, each Vse switch is connected to the gate of each MOSFET, the drain of each MOSFET is connected to a SW switch, the MOSFET drain current is connected through the SW switch, and the source of each MOSFET is grounded; the ratio of the MOSFET length and the MOSFET channel width in the MOSFET combination in the zero temperature drift coefficient circuit is adjusted by rotating different combinations of closed SW switches, and coordinated with the closed switch combination selected in the bias voltage generating circuit to adjust the output voltage to a specific voltage, thereby outputting a higher precision constant temperature reference current source.

[0009] The bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to a reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mn, the drain is connected to the VDD voltage terminal, and the source is connected in series with a R1n resistor string and a R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0010] The bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to a reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mp, the source terminal is connected to the VDD voltage terminal, and the drain terminal is connected in series with a R1n resistor string and a R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0011] The zero temperature drift coefficient circuit includes only one MOS tube, each Vse switch is connected to the gate of the MOS tube, the drain is connected to the drain current of the MOS tube, and the source is grounded.

[0012] The present invention has the following advantages: a constant temperature reference current source with zero temperature drift coefficient, a simple overall structure, no need to use devices such as resistors, can avoid the decrease in accuracy caused by the temperature coefficient of the resistor, and reduce the cost; any specific V can be achieved by controlling the closing of the Vse switch bias Voltage is used to turn on the zero temperature drift coefficient circuit, thereby generating a reference current with a zero temperature drift coefficient; or a high-precision constant temperature reference current source for various currents can be achieved by selecting different MOS tube W / L ratios. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A circuit diagram of an existing reference current source;

[0014] Figure 2 It is a schematic diagram of a circuit diagram of the present invention;

[0015] Figure 3 A circuit diagram of a first embodiment of the present invention;

[0016] Figure 4 is a circuit diagram of Embodiment 2 of the present invention;

[0017] Figure 5 is a circuit diagram of Embodiment 3 of the present invention;

[0018] Figure 6 This is a circuit diagram of embodiment 4 of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application provided below in conjunction with the drawings is not intended to limit the scope of protection of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The present invention is further described below in conjunction with the drawings.

[0020] like Figure 2 As shown, the present invention relates to a constant temperature reference current source with a zero temperature drift coefficient, which includes a bias voltage generating circuit and a zero temperature drift coefficient circuit; the bias voltage generating circuit generates a specific voltage and inputs it into the zero temperature drift coefficient circuit, so that the zero temperature drift coefficient circuit is turned on, thereby generating a reference current with a zero temperature drift coefficient. The zero temperature drift coefficient circuit only includes a MOS tube, each Vse switch is connected to the gate of the MOS tube, the drain is connected to the MOS tube drain current, and the source is grounded.

[0021] The calculation process of the specific bias voltage is: Then get Iref is the drain current of MOS tube; μ n is the mobility of the MOS tube; C ox is the gate oxide capacitance of the MOS tube; W is the length of the MOS tube; L is the channel width of the MOS tube; Vref is the gate voltage of the MOS tube; V T is the threshold voltage of the MOS tube; Iref(T) is the drain current of the MOS tube expressed in temperature; a vt is the temperature coefficient of the threshold voltage; a u is the temperature coefficient of mobility.

[0022] Furthermore, the threshold voltage of the MOS tube (V T ) shows negative temperature characteristics (a vt is a negative number), the mobility of the MOS tube is a positive temperature characteristic (a u is a positive number), when V bias The voltage meets V bias =V T (T0)-a vt At T0, the temperature characteristic of Iref(T) depends on Extensive device characterization studies have shown that the temperature dependence of mobility in modern processes is a u is -2; therefore the MOS tube operates at a specific bias voltage V bias There will be a conduction characteristic with zero temperature drift coefficient. This characteristic of the MOS tube can be used to generate a reference current with zero temperature drift coefficient.

[0023] Example 1

[0024] like Figure 3 As shown, the bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to the reference voltage source, and the output terminal of the comparator is connected in series with the R1n resistor string and the R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a Vse switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each Vse switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0025] The zero temperature drift coefficient circuit includes only one MOS tube, each Vse switch is connected to the gate of the MOS tube, the drain is connected to the MOS tube drain current Iref, and the source is grounded.

[0026] R1n is a resistor string made up of n resistors in series, and the nodes of the series resistors are all connected and controlled by a switch; R2m is a resistor string made up of m resistors in series, and the nodes of the series resistors are all connected and controlled by a switch; finally, any output V can be realized by closing a Vsel switch. bias , so that V bias =V T (T0)-a vt T0.

[0027] Example 2

[0028] like Figure 4 As shown, the bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to the reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mn, the drain is connected to the VDD voltage terminal, and the source is connected in series with the R1n resistor string and the R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0029] The zero temperature drift coefficient circuit includes only one MOS tube, each Vse switch is connected to the gate of the MOS tube, the drain is connected to the MOS tube drain current Iref, and the source is grounded.

[0030] R1n is a resistor string realized by n resistors in series, and the nodes of the series resistors are all led out and controlled by a switch; R2m is a resistor string realized by m resistors in series, and the nodes of the series resistors are all led out and controlled by a switch; the implementation method of this embodiment provides greater driving capability and improves PSRR (power supply rejection ratio) by adding a MOS tube Mn in the negative feedback; finally, any output V can be realized by closing a certain Vsel switch bias , so that V bias =V T (T0)-a vt T0.

[0031] Example 3

[0032] like Figure 5 As shown, the bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to the reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mp, the source terminal is connected to the VDD voltage terminal, and the drain terminal is connected in series with the R1n resistor string and the R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0033] The zero temperature drift coefficient circuit includes only one MOS tube, each Vse switch is connected to the gate of the MOS tube, the drain is connected to the MOS tube drain current Iref, and the source is grounded.

[0034] R1n is a resistor string realized by n resistors in series, and the nodes of the series resistors are all led out and controlled by a switch; R2m is a resistor string realized by m resistors in series, and the nodes of the series resistors are all led out and controlled by a switch; the implementation method of this embodiment provides greater driving capability and improves PSRR (power supply rejection ratio) by adding a MOS tube Mp in the negative feedback; the circuit structure of this embodiment is different from that of embodiment 3 in that it can work at a lower power supply voltage; finally, any output V can be realized by closing a certain Vsel switch bias , so that V bias =V T (T0)-a vt T0.

[0035] Example 4

[0036] like Figure 6As shown, the bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to the reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mn, the drain is connected to the VDD voltage terminal, and the source is connected in series with the R1n resistor string and the R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

[0037] The zero temperature drift coefficient circuit includes multiple MOS tubes connected in parallel, each Vse switch is connected to the gate of each MOS tube, the drain of each MOS tube is connected to a SW switch, the MOS tube drain current is connected through the SW switch, and the source of each MOS tube is grounded.

[0038] R1n is a resistor string made up of n resistors in series, and the nodes of the series resistors are all connected and controlled by a switch; R2m is a resistor string made up of m resistors in series, and the nodes of the series resistors are all connected and controlled by a switch; any output V can be realized by closing a Vsel switch bias , so that V bias =V T (T0)-a vt T0; by selecting different W / L through switches (SW1, SW2, ..., SWn), a high-precision constant temperature reference current source with various output currents can be realized.

[0039] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A constant temperature reference current source with zero temperature drift coefficient, characterized in that: It includes a bias voltage generating circuit and a zero temperature drift coefficient circuit; a plurality of switches are provided at the voltage output end of the bias voltage generating circuit, and a specific voltage is output by selecting a combination of closed switches, generating a specific voltage which is input into the zero temperature drift coefficient circuit, so that the MOS tube in the zero temperature drift coefficient circuit is turned on, thereby generating a reference current with a zero temperature drift coefficient; The zero temperature drift coefficient circuit includes a plurality of MOSFET combinations connected in parallel, each switch in the bias voltage generating circuit is connected to the gate of each MOSFET, the drain of each MOSFET is connected to a SW switch, the MOSFET drain current is connected through the SW switch, and the source of each MOSFET is grounded; the ratio of the MOSFET length and the MOSFET channel width in the MOSFET combination in the zero temperature drift coefficient circuit is adjusted by selecting different combinations of closed SW switches, and the ratio is adjusted in coordination with the closed switch combination selected in the bias voltage generating circuit so that the output voltage is a specific voltage, thereby outputting a higher precision constant temperature reference current source; The specific voltage is calculated by: Then get Where Iref is the drain current of the MOS tube; μ n is the mobility of the MOS tube; C ox is the gate oxide capacitance of the MOS tube; W is the length of the MOS tube; L is the channel width of the MOS tube; Vref is the gate voltage of the MOS tube; V T is the threshold voltage of the MOS tube; Iref(T) is the drain current of the MOS tube expressed in temperature; a vt is the temperature coefficient of the threshold voltage; a u is the temperature coefficient of mobility; When V bias The voltage meets V bias =V T (T0)-a vt At T0, the temperature characteristic of Iref(T) depends on Therefore, the MOS tube works at a specific bias voltage V bias There is a conduction characteristic with zero temperature drift coefficient under the condition. This characteristic of the MOS tube can be used to generate a reference current with zero temperature drift coefficient.

2. The constant temperature reference current source with zero temperature drift coefficient according to claim 1, characterized in that: The bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to a reference voltage source, and the output terminal of the comparator is connected in series with an R1n resistor string and an R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a Vse switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each Vse switch is connected to the input terminal of the zero temperature drift coefficient circuit.

3. The constant temperature reference current source with zero temperature drift coefficient according to claim 1, characterized in that: The bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to a reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mn, the drain is connected to the VDD voltage terminal, and the source is connected in series with a R1n resistor string and a R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

4. The constant temperature reference current source with zero temperature drift coefficient according to claim 1, characterized in that: The bias voltage generating circuit includes a comparator, the positive input terminal of the comparator is connected to a reference voltage source, the output terminal of the comparator is connected to the gate of the MOS tube Mp, the source terminal is connected to the VDD voltage terminal, and the drain terminal is connected in series with a R1n resistor string and a R2n resistor string; the R1n resistor string and the R2n resistor string are both obtained by connecting n resistors in series, and each node of the series resistors is connected in parallel with a switch to control the gating; the negative input terminal of the comparator is connected to the series terminal of the R1n and R2n resistor strings; each switch is connected to the input terminal of the zero temperature drift coefficient circuit.

5. A constant temperature reference current source with zero temperature drift coefficient according to any one of claims 2 to 4, characterized in that: The zero temperature drift coefficient circuit includes only one MOS tube, each Vse switch is connected to the gate of the MOS tube, the drain is connected to the drain current of the MOS tube, and the source is grounded.

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