Dual-channel ultralow temperature drift constant current source circuit

Abstract

The invention relates to the field of high-precision ultralow-temperature-drift constant-current sources, in particular to a dual-channel ultralow-temperature-drift constant-current source circuit which comprises a temperature drift coefficient trimmable reference source circuit, an offset compensation loop, a matched resistor network, a Darlington driving output circuit, an amplifier and a reference working point adjusting resistor. According to the invention, the resistor network composed of resistors with different temperature coefficients is constructed, the temperature drift coefficient of the resistor network is changed, the effect which can be achieved by a complex circuit structure of a traditional ultralow temperature drift constant current source is realized, ultralow temperature drift within 1ppm / DEG C is realized by using a conventional structure, all comprehensive compensation is carried out on errors and maladjustment, and the ultra-low temperature drift constant current source has the advantages of small size, low cost, high reliability and the like. And ultralow temperature bleaching is realized.

Description

Technical Field

[0001] The present invention relates to the field of high-precision ultra-low temperature drift constant current sources, and in particular to a dual-channel ultra-low temperature drift constant current source circuit. Background Art

[0002] In the field of high-precision, ultra-low temperature drift constant current sources, in order to achieve ultra-low temperature drift, people usually look for ultra-low temperature drift references and ultra-low temperature drift resistors, as well as low offset op amps.

[0003] The implementation of an ultra-low temperature drift reference usually adopts a segmented multi-stage compensation circuit structure or digital adjustment technology, which will introduce a complex circuit structure. In addition, the ultra-low temperature drift reference is affected by packaging or mounting stress during application, making it difficult to achieve the optimal state and the price is high.

[0004] The realization of ultra-low temperature drift resistors is even more difficult. At present, the temperature drift coefficient of domestic metal film resistors can reach a maximum accuracy of 5ppm / ℃, and foreign metal film resistors can achieve below 1ppm / ℃; however, ultra-low temperature drift resistors have a narrow operating range, large resistor volume, and cannot be miniaturized. They are also expensive. The metal film resistors sold by international precision resistor manufacturers represented by Vishay Precision Group (VPG) are worth about 500 yuan per resistor.

[0005] Therefore, there is an urgent need for a small-sized ultra-low temperature drift constant current source circuit. Summary of the Invention

[0006] In view of this, the present invention discloses a dual-channel ultra-low temperature drift constant current source circuit to solve the above problems;

[0007] A dual-channel ultra-low temperature drift constant current source circuit, comprising: a reference source circuit with adjustable temperature drift coefficient, an offset compensation loop, a matching resistor network, a Darlington drive output circuit, an amplifier, and a reference operating point adjustment resistor;

[0008] One end of the temperature drift coefficient adjustable reference source circuit is connected to a matching resistor network, and the other end is respectively connected to a non-inverting input of an amplifier and a reference operating point adjustment resistor; the other end of the reference operating point adjustment resistor is grounded; the other end of the matching resistor network is connected to an offset compensation loop; the offset compensation loop is further respectively connected to an inverting input of the amplifier and an emitter of a Darlington drive output circuit; the base of the Darlington drive output circuit is connected to the output of the amplifier, and the collector is connected to a load;

[0009] Furthermore, the dual-channel ultra-low temperature drift constant current source circuit includes a positive constant current channel and a negative constant current channel, the Darlington drive output circuit of the positive constant current channel adopts a PNP tube, and the Darlington drive output circuit of the negative constant current channel adopts an NPN tube;

[0010] Furthermore, the reference operating point adjustment resistor is used to set the voltage operating point of the dual-channel ultra-low temperature drift constant current source circuit;

[0011] Furthermore, the temperature drift coefficient adjustable reference source circuit includes: 7 resistors R1 to R7, 13 transistors Q1 to Q13, and a polarized capacitor C1; wherein the base of Q1 is respectively connected to one end of R1 and one end of R2; the other end of R1 is respectively connected to one end of R3, the emitter of Q2, the emitter of Q3, one end of R6, the emitter of Q8, the emitter of Q11, the emitter of Q12, and the collector of Q13; the other end of R2 is respectively connected to the collector of Q1, the emitter of Q6, the emitter of Q7, the emitter of Q9, the emitter of Q10, one end of R7, and the emitter of Q13; the other end of R3 is respectively connected to one end of R4 and the base of Q5; the other end of R4 is respectively connected to Connect one end of R5 to the base of Q4; the other end of R5 is connected to the emitter of Q1; the collector of Q2 is connected to the base of Q2, the base of Q3 and the collector of Q4 respectively; the collector of Q3 is connected to the collector of Q5, the base of Q8 and the negative terminal of C1 respectively; the emitter of Q4 is connected to the emitter of Q5 and the collector of Q6 respectively; the base of Q6 is connected to the base of Q7, the collector of Q7, the other end of R6 and the base of Q9 respectively; the collector of Q8 is connected to the positive terminal of C1, the collector of Q9 and the base of Q10 respectively; the collector of Q10 is connected to the collector of Q11, the base of Q11 and the base of Q12 respectively; the collector of Q12 is connected to the other end of R7 and the base of Q13 respectively;

[0012] Furthermore, Q1, Q2, Q3, Q8, Q11 and Q12 are PNP transistors, and Q4, Q5, Q6, Q7, Q9, Q10 and Q13 are NPN transistors; the emitter areas of Q2 and Q3 are equal;

[0013] R4 and R5 are R CS Resistor, with a positive temperature coefficient; resistor R3 is composed of two different types of resistors R31 and R32 in series; R31 has a positive temperature coefficient, R32 is R PB resistors, with negative temperature coefficients;

[0014] Furthermore, the matching resistor network, as the feedback resistor in the constant current source circuit, is composed of R CS The series combination of similar resistors is used to match the bandgap reference circuit, and the temperature drift coefficient is consistent with that of the bandgap reference circuit;

[0015] Furthermore, an offset compensation loop is used to compensate for the offset voltage of the dual-channel ultra-low temperature drift constant current source circuit and is implemented based on a dual operational amplifier circuit.

[0016] The beneficial effects of the present invention include:

[0017] The structure designed by the present invention achieves the effect that can only be achieved by the complex circuit structure of the traditional ultra-low temperature drift constant current source by constructing a resistor network formed by resistors with different temperature coefficients and changing the temperature drift coefficient of the resistor network. The conventional structure realizes ultra-low temperature drift within 1ppm / ℃, and at the same time realizes a small size of 10mm×10mm×2.1mm. It comprehensively compensates for all errors and offsets, and has the characteristics of small size, low cost and ultra-low temperature drift.

[0018] At present, there is no constant current source circuit in China that can simultaneously achieve a temperature drift coefficient of ≤1ppm / ℃ and a size smaller than 10mm×10mm×2.1mm. The present invention provides a new design idea for the field of ultra-low temperature drift constant current sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the circuit structure of the dual-channel ultra-low temperature drift constant current source circuit in the present invention;

[0020] Figure 2 Schematic diagram of a reference source circuit with adjustable temperature drift coefficient according to an embodiment of the present invention;

[0021] Figure 3 The simulation test results of the dual-channel ultra-low temperature drift constant current source circuit in the embodiment of the present invention are as follows;

[0022] Figure 4 1 is a circuit diagram of an offset compensation loop in an embodiment of the present invention;

[0023] Figure 5 This is an assembly diagram of a dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention;

[0024] Figure 6 This is a design diagram of the front side of the SIP integrated housing of the dual-channel ultra-low temperature drift constant current source device according to an embodiment of the present invention;

[0025] Figure 7 This is a design diagram of the side of the SIP integrated housing of the dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention;

[0026] Figure 8 This is a design diagram of the back side of the SIP integrated housing of the dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention;

[0027] Figure 9 This is the reverse side of the SIP integrated housing of the dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention;

[0028] Figure 10 This is the front side of the SIP integrated housing of the dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention;

[0029] Figure 11This is the test result of the positive current output of the dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention;

[0030] Figure 12 This is the test result of the negative current output of the dual-channel ultra-low temperature drift constant current source device in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions, features and advantages of the present invention more clearly understood, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1:

[0033] This embodiment includes a dual-channel ultra-low temperature drift constant current source circuit, such as Figure 1 As shown, it includes: a reference source circuit with adjustable temperature drift coefficient, an offset compensation loop, a matching resistor network, a Darlington drive output circuit, an amplifier, and a reference operating point adjustment resistor.

[0034] One end of the temperature drift coefficient adjustable reference source circuit is connected to a matching resistor network, and the other end is respectively connected to the non-inverting input of the amplifier and the reference operating point adjustment resistor; the other end of the reference operating point adjustment resistor is grounded; the other end of the matching resistor network is connected to an offset compensation loop; the offset compensation loop is also respectively connected to the inverting input of the amplifier and the emitter of the Darlington drive output circuit; the base of the Darlington drive output circuit is connected to the output of the amplifier, and the collector is connected to the load.

[0035] The reference operating point adjustment resistor is used to set the voltage operating point of the dual-channel ultra-low temperature drift constant current source circuit.

[0036] The temperature drift coefficient can be adjusted to adjust the reference source circuit, such as Figure 2As shown, it includes: 7 resistors R1 to R7, 13 transistors Q1 to Q13, and a polarized capacitor C1; the base of Q1 is respectively connected to one end of R1 and one end of R2; the other end of R1 is respectively connected to one end of R3, the emitter of Q2, the emitter of Q3, one end of R6, the emitter of Q8, the emitter of Q11, the emitter of Q12, and the collector of Q13; the other end of R2 is respectively connected to the collector of Q1, the emitter of Q6, the emitter of Q7, the emitter of Q9, the emitter of Q10, one end of R7, and the emitter of Q13; the other end of R3 is respectively connected to one end of R4 and the base of Q5; the other end of R4 is respectively connected to one end of R5 and Q4 The base of Q7, the collector of Q7, the other end of R6 and the base of Q9 are connected respectively; the collector of Q8 is connected to the positive electrode of C1, the collector of Q9 and the base of Q10; the collector of Q10 is connected to the collector of Q11, the base of Q11 and the base of Q12; the collector of Q12 is connected to the other end of R7 and the base of Q13.

[0037] Among them, Q1, Q2, Q3, Q8, Q11 and Q12 are PNP transistors, Q4, Q5, Q6, Q7, Q9, Q10 and Q13 are NPN transistors; R3~R5, Q1~Q6 constitute a bandgap reference circuit, the emitter area ratio of the core pair of tubes Q4 and Q5 of the bandgap reference circuit is N:1, and the emitter areas of Q2 and Q3 are equal. R4 and R5 are R CS Resistor, with a positive temperature coefficient; resistor R3 is composed of two different types of resistors R31 and R32 in series; R31 has a positive temperature coefficient, R32 is R PB Resistors with negative temperature coefficients. Figure 2 The red box in the middle indicates the circuit portion that affects the reference temperature drift of the bandgap reference circuit.

[0038] The bandgap reference circuit includes a resistor network with different temperature coefficients, which is composed of positive temperature resistors and negative temperature resistors. The present invention uses laser trimming to change the temperature drift coefficient of the resistor network. By adjusting the temperature drift coefficient, the temperature drift coefficient can be adjusted to adjust the reference source circuit to output different reference voltages.

[0039] Furthermore, the emitter of Q2 is connected to the reference voltage V ref , the base of Q1 is connected to the matching resistor network, and the collector of Q1 is grounded.

[0040] The matching resistor network is used as the feedback resistor in the constant current source circuit. CSThe series combination of similar resistors is used to match the bandgap reference circuit, and the temperature drift coefficient is consistent with that of the bandgap reference circuit.

[0041] The offset compensation loop compensates the offset voltage of the dual-channel ultra-low temperature drift constant current source circuit based on the offset of the operational amplifier itself. The offset compensation loop used in this embodiment is as follows: Figure 4 As shown, including operational amplifier OPAB and resistor R8, Figure 4 OPAA Figure 1 The OPAB, the mid-amplifier, uses a follower design, inputting its offset voltage into the inverting input of the OPAA, thereby canceling the offset voltage at the non-inverting input of the OPAA. The OPAA, Darlington driver output circuit, R8, and the OPAB form a feedback loop. The offset compensation loop designed in this invention is based on a dual op amp circuit. Because the OPAA and OPAB are two channels within the same chip, theoretically, they can completely cancel out the op amp's offset voltage.

[0042] Darlington driver output circuit, such as Figure 1 As shown in the middle Q, it has the characteristics of strong driving capability and can reduce the influence of op amp offset. The dual-channel ultra-low temperature drift constant current source circuit includes a positive constant current channel and a negative constant current channel. The Darlington drive output circuit of the positive constant current channel adopts a PNP tube, and the Darlington drive output circuit of the negative constant current channel adopts an NPN tube.

[0043] When the circuit is in operation, the temperature drift coefficient can be adjusted by adjusting the resistance values ​​of R3 and R5, and the reference source circuit can generate reference voltages with different temperature drift coefficients. The offset compensation loop eliminates the offset voltage of the amplifier, and the matching resistor network serves as a sampling resistor to sample both ends of the matching resistor network. The sampled voltage is compared with the reference voltage, and the compared signal is amplified by the amplifier. The Darlington drive output circuit adjusts the current to achieve a constant current output.

[0044] Furthermore, the bandgap reference voltage represents the reference voltage V ref The difference between the voltage at the ADJ port and the voltage at the two ends of R1; the ADJ port represents the port where the temperature drift coefficient can be adjusted and the reference source circuit is connected to the matching resistor network, that is, the base of Q1. The formula is:

[0045]

[0046] Among them, V BG Represents the bandgap reference voltage, V ref Indicates the reference voltage, V ADJ Indicates the ADJ port voltage, V EB1= represents the base-emitter voltage of Q1, VT represents the thermal voltage, and the calculation formula is VT = kT / q, where k is the Boltzmann constant, T represents the temperature, q represents the electron charge, and N represents the emitter area ratio of Q4 and Q5. PB Resistance, the above formula can be expressed as:

[0047]

[0048] Since the two types of resistors have different temperature drift coefficients, by adjusting the resistance values ​​of R32 and R5, a reference output with different temperature drift coefficients can be generated. Specifically, the present invention uses laser trimming to adjust the resistance values ​​of R32 and R5, thereby changing the temperature drift curve of the reference. The output constant current value is determined by the reference voltage and the feedback resistor, and the formula is:

[0049]

[0050] Among them, I O Indicates the constant current source output, V re f represents the reference voltage, R s Indicates the resistance of the matching resistor network.

[0051] like Figure 3 As shown in the simulation waveform, within the full temperature range of -55°C to 125°C, the maximum change of the dual-channel ultra-low temperature drift constant current source circuit designed by the present invention is Δ2.1μA, and the temperature drift coefficient is 0.59ppm / °C.

[0052] Example 2:

[0053] This embodiment includes a dual-channel ultra-low temperature drift constant current source circuit, which is specifically implemented by a dual-channel ultra-low temperature drift constant current source device, adopts a SIP (System In a Package) integrated housing design, and has an external size of 10mm×10mm×2.1mm.

[0054] The SIP one-piece molded housing includes: a substrate, a sealing ring and a cover plate. Among them, the substrate design is the core design. In this embodiment, the substrate is provided with 5 layers. The first layer is the bonding interconnection area; the second layer is the chip mounting area; the third layer is the inner layer signal routing interconnection area; the fourth layer is the ground layer; and the fifth layer is the lead-out terminal interconnection area.

[0055] The substrate is made of Al2O3 ceramic material and has dimensions of 10mm×10mm×1.1mm. The inner cavity chip welding area of ​​the substrate adopts a sinking cavity design. The sinking cavity design can effectively reduce the distance between the bonding area and the chip during wire bonding, thereby achieving the purpose of reducing the size of the SIP. The back of the substrate is the output pin of the entire SIP circuit. This embodiment adopts a QFN (Quad Flat No-lead) structure with a half-hole design on the edge to prevent solder creep during soldering and increase soldering reliability.

[0056] The sealing ring is made of 4J29 material, with dimensions of 8.5mm×8.50mm×1.0mm and thickness of 0.5mm.

[0057] The cover is made of 4J42 material with a size of 9.4mm×9.4mm×0.1mm, and the sealing cap is parallel welded.

[0058] Gold wire bonding is used between the substrate, sealing ring and cover plate. The chip is set on the substrate and assembled with high temperature solder paste. Figure 5 As shown, this embodiment integrates an adjustable reference, a matching resistor network, an NPN driver Darlington transistor, and a Darlington driver output circuit on a single chip, thereby ensuring device temperature consistency. IC1 and IC2 are adjustable reference chips, and OPA1 and OPA2 are dual-channel operational amplifiers.

[0059] In this embodiment, the temperature drift coefficient can be adjusted. The reference source circuit and the matching resistor network are designed on the same silicon chip. The matching resistor network R s By R CS The resistor composition is similar, and the consistency and material properties are consistent, which solves the matching problem. At this time, the reference temperature drift can be adjusted to match R s Temperature drift curve, reference temperature drift and R s The temperature drift curve is consistent with that of the CMOS, so ultra-low temperature drift design can be achieved.

[0060] Figure 6 、 Figure 7 、 Figure 8 This is a SIP integrated housing design diagram of the dual-channel ultra-low temperature drift constant current source device in this embodiment.

[0061] Figure 9 、 Figure 10 This is a physical picture of the dual-channel ultra-low temperature drift constant current source device in this embodiment.

[0062] Furthermore, the actual test results of the dual-channel ultra-low temperature drift constant current source device in this embodiment are as follows: Figure 11 、 Figure 12As shown, the horizontal axis represents temperature and the vertical axis represents output current. It can be seen from the figure that the temperature coefficient of I+ is 0.46ppm / ℃, the temperature coefficient of I- is 0.21ppm / ℃, and I+ and I- indicate opposite current directions during the test.

[0063] Finally, it should be noted that the above only describes some embodiments of the present invention. For those skilled in the art, it is conceivable that various changes, modifications, substitutions and deformations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents, and the above-mentioned actions should be covered within the scope of protection of the present invention.

Claims

1. A dual-channel ultra-low temperature drift constant current source circuit, characterized in that: include: The temperature drift coefficient can be adjusted for the reference source circuit, offset compensation loop, matching resistor network, Darlington drive output circuit, amplifier, and reference operating point adjustment resistor; Among them, one end of the temperature drift coefficient adjustable reference source circuit is connected to the matching resistor network, and the other end is respectively connected to the non-inverting input terminal of the amplifier and the reference operating point adjustment resistor; the other end of the reference operating point adjustment resistor is grounded; the other end of the matching resistor network is connected to the offset compensation loop; the offset compensation loop is also respectively connected to the inverting input terminal of the amplifier and the emitter of the Darlington drive output circuit; the base of the Darlington drive output circuit is connected to the output terminal of the amplifier, and the collector is connected to the load.

2. The dual-channel ultra-low temperature drift constant current source circuit according to claim 1, characterized in that: The dual-channel ultra-low temperature drift constant current source circuit includes a positive constant current channel and a negative constant current channel. The Darlington drive output circuit of the positive constant current channel adopts a PNP tube, and the Darlington drive output circuit of the negative constant current channel adopts an NPN tube.

3. The dual-channel ultra-low temperature drift constant current source circuit according to claim 1, characterized in that: The temperature drift coefficient adjustable reference source circuit includes: 7 resistors R1 to R7, 13 transistors Q1 to Q13, and polarized capacitor C1; among which: The base of Q1 is connected to one end of R1 and one end of R2 respectively; The other end of R1 is connected to one end of R3, the emitter of Q2, the emitter of Q3, one end of R6, the emitter of Q8, the emitter of Q11, the emitter of Q12 and the collector of Q13; The other end of R2 is connected to the collector of Q1, the emitter of Q6, the emitter of Q7, the emitter of Q9, the emitter of Q10, one end of R7 and the emitter of Q13; The other end of R3 is connected to one end of R4 and the base of Q5 respectively; The other end of R4 is connected to one end of R5 and the base of Q4 respectively; The other end of R5 is connected to the emitter of Q1; The collector of Q2 is connected to the base of Q2, the base of Q3 and the collector of Q4; The collector of Q3 is connected to the collector of Q5, the base of Q8 and the negative terminal of C1; The emitter of Q4 is connected to the emitter of Q5 and the collector of Q6 respectively; The base of Q6 is connected to the base of Q7, the collector of Q7, the other end of R6 and the base of Q9; The collector of Q8 is connected to the positive terminal of C1, the collector of Q9 and the base of Q10 respectively; The collector of Q10 is connected to the collector of Q11, the base of Q11 and the base of Q12 respectively; The collector of Q12 is connected to the other end of R7 and the base of Q13 respectively; The emitter of Q2 is connected to the reference voltage, the base of Q1 is connected to the matching resistor network, and the collector of Q1 is grounded.

4. The dual-channel ultra-low temperature drift constant current source circuit according to claim 3, characterized in that: Q1, Q2, Q3, Q8, Q11 and Q12 are PNP transistors, and Q4, Q5, Q6, Q7, Q9, Q10 and Q13 are NPN transistors; the emitter area ratio of Q4 and Q5 is N:1, and the emitter areas of Q2 and Q3 are equal; R4 and R5 have positive temperature coefficients; R3 is composed of two different types of resistors R31 and R32 connected in series, R31 has a positive temperature coefficient, and R32 has a negative temperature coefficient.

5. The dual-channel ultra-low temperature drift constant current source circuit according to claim 3, characterized in that: R3~R5 and Q1~Q6 constitute a bandgap reference circuit, which includes a resistor network with different temperature coefficients. The temperature drift coefficient of the resistor network is changed by laser trimming, and the temperature drift coefficient can be used to adjust the reference source circuit to output different reference voltages.

6. The dual-channel ultra-low temperature drift constant current source circuit according to claim 5, characterized in that: The following relationship exists when the bandgap reference circuit works: Among them, V BG Represents the voltage difference between the two ends of R1, V ref Indicates the reference voltage, V EB1 is the base-emitter voltage of Q1, VT is the thermal voltage, and N is the emitter area ratio of Q4 to Q5.

7. The dual-channel ultra-low temperature drift constant current source circuit according to claim 1, characterized in that: The offset compensation loop is used to compensate for the offset voltage of the dual-channel ultra-low temperature drift constant current source circuit and is implemented based on a dual operational amplifier circuit.

8. The dual-channel ultra-low temperature drift constant current source circuit according to claim 1, characterized in that: The reference operating point adjustment resistor is used to set the voltage operating point of the dual-channel ultra-low temperature drift constant current source circuit.

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