High-precision reference voltage starting circuit

Abstract

The application discloses a high-precision reference voltage starting circuit, which comprises a starting current ISTART, a control switch SW1, a current detection MST, a reference current IREF, a filter circuit and a comparator circuit, one end of the starting current ISTART is connected with a drain electrode of the current detection MST, the other end is connected with the control switch SW1, and an output end of the control switch SW1 is connected with a VA node. The high-precision reference voltage starting circuit adopts a current source for the current of the VA node, controls the intensity of injection, further eliminates noise burrs through CMP1, thereby eliminating ringing, solves the error and ringing problems introduced by the reference starting circuit, guarantees that the reference is in a temperature range of -40 DEG C to 125 DEG C, realizes that the reference temperature drift is less than or equal to 1 mV, and guarantees that the reference has no ringing problem in the starting process.

Description

Technical Field

[0001] This invention relates to the field of analog integrated circuits, and more particularly to a high-precision reference voltage startup circuit. Background Technology

[0002] In analog integrated circuits, a high-precision reference is required to achieve high-precision analog-to-digital (ADC) / digital-to-analog (DAC) conversion. Achieving a reference temperature drift of ≤1mV within a temperature range of -40℃ to 125℃ is a fundamental requirement for high-precision converters. In industrial applications, first-order and second-order compensation methods have been proposed to achieve a temperature drift of ≤1mV. However, while achieving a high-precision reference, the reference's startup circuit typically introduces errors, causing the temperature drift to exceed 1mV. Furthermore, the reference's startup circuit often suffers from ringing, leading to instability during the startup process. Summary of the Invention

[0003] To solve the above-mentioned ringing problem, this invention proposes a high-precision reference voltage start-up circuit.

[0004] A high-precision reference voltage start-up circuit includes a start-up current ISTART, a control switch SW1, a current sensor MST, a reference current IREF, a filter circuit, and a comparator circuit. One end of the start-up current ISTART is connected to the drain of the current sensor MST, and the other end is connected to the control switch SW1. The output of the control switch SW1 is connected to the VA node.

[0005] Specifically, the source of the current sensing MST is connected to the filter circuit and the reference current IREF, with the connection point being the VN node, and the gate of the current sensing MST is connected to the output.

[0006] Specifically, the "+" input terminal of the comparator circuit is connected to the other end of the filter circuit, the "-" input terminal is connected to the positive terminal of VR, and the output terminal is connected to the control switch SW1.

[0007] Specifically, the control switch SW1 can be a transmission gate or a single tube.

[0008] Specifically, the current sensing MST is a current mirror, which can be implemented using a single tube or a Cascade structure mirror.

[0009] Specifically, the starting current ISTART is a constant current source.

[0010] Specifically, the filter circuit can adopt a resistor R-capacitor C structure, a capacitor C-resistor R-capacitor C structure, or an inductor L-capacitor C structure.

[0011] Specifically, when the circuit starts up, the starting current ISTART injects current into the VA node to eliminate base current error.

[0012] Specifically, the filter circuit and comparator circuit control the current injection switch in the startup circuit detection loop to eliminate ringing.

[0013] The beneficial effects of this invention are as follows: This invention proposes a high-precision reference voltage startup circuit, including a startup current ISTART, a control switch SW1, a current sensor MST, a reference current IREF, a filter circuit, and a comparator circuit. One end of the startup current ISTART is connected to the drain of the current sensor MST, and the other end is connected to the control switch SW1. The output of the control switch SW1 is connected to the VA node. This high-precision reference voltage startup circuit uses a current source to control the injection intensity of the current at the VA node. Furthermore, the filter circuit shapes and filters the voltage at the VN node, eliminating high-frequency glitches. The CMP1 further eliminates noise glitches, thereby eliminating ringing. This solves the error and ringing problems introduced by the reference startup circuit, ensuring that the reference temperature drift is ≤1mV within the temperature range of -40℃ to 125℃, and ensuring that there is no ringing problem during the startup process. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a high-precision reference voltage structure in existing technology;

[0015] Figure 2 This is a schematic diagram of a high-precision reference voltage structure in existing technology;

[0016] Figure 3 Temperature curve of existing high-precision reference voltage;

[0017] Figure 4 This is a schematic diagram of a high-precision reference voltage start-up circuit based on existing technology.

[0018] Figure 5 This is a schematic diagram of the high-precision reference voltage start-up circuit of the present invention;

[0019] Figure 6 This is a diagram illustrating an implementation of the high-precision reference voltage startup circuit of the present invention.

[0020] Figure 7 This is a schematic diagram of the transfer characteristics of an existing hysteresis comparator. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0022] This invention proposes a high-precision reference voltage startup circuit, including a startup current ISTART, a control switch SW1, a current sensor MST, a reference current IREF, a filter circuit, and a comparator circuit. One end of the startup current ISTART is connected to the drain of the current sensor MST, and the other end is connected to the control switch SW1. The output of the control switch SW1 is connected to the VA node. The source of the current sensor MST is connected to the filter circuit and the reference current IREF at the VN node, and the gate of the current sensor MST is connected to the output. Specifically, the "+" input of the comparator circuit is connected to the other end of the filter circuit, the "-" input is connected to the positive terminal of VR, and the output is connected to the control switch SW1. The control switch SW1 can be a transmission gate or a single transistor. The current sensor MST is a current mirror, which can be implemented using a single transistor or a Cascade structure. The startup current ISTART is a constant current source. The filter circuit can adopt a resistor R-capacitor C structure, a capacitor C-resistor R-capacitor C structure, or an inductor L-capacitor C structure.

[0023] like Figure 1 As shown, in the existing high-precision reference voltage structure, a zero-temperature current is obtained by adding a positive temperature coefficient current (PTAT) and a negative temperature coefficient current (NTAT); the zero-temperature current is then allowed to flow through a resistor to generate a zero-temperature coefficient voltage.

[0024] Generation of zero-temperature current: ;

[0025] in, For negative temperature coefficient current, This is the positive temperature coefficient current.

[0026] The reference voltage is generated through: ;

[0027] .

[0028] The mirror current can be set by adjusting the value of K (mirror ratio); the absolute value of the reference voltage can be set by adjusting the value of R3; and the zero-temperature current can be obtained by adjusting the ratio of R2 and R1. From the expression for VREF, it can be seen that when VREF is first-order compensated, it is difficult to meet the requirement of temperature drift ≤1mV.

[0029] refer to Figure 2 The high-precision reference voltage structure introduces R4 and R5, Q3 and M3, and allows Q3 to be biased in a zero-temperature current state to generate a second-order compensation voltage. The difference between Q3 and the voltage at the VA and VB nodes generates a second-order compensation current.

[0030] Through a detailed analysis of VBE, it can be seen that: ;

[0031] It is the bandgap voltage. The temperature is The BE junction voltage, This is a process-related constant, typically 4. Constants related to BJT bias current.

[0032] When the bias current is PTAT, it is close to 1;

[0033] When the bias current is the zero-temperature current, it is close to 0;

[0034] Because Q1 and Q2 are biased with PTAT current, therefore:

[0035] ;

[0036] Q3 is biased at zero temperature current, therefore: ;

[0037] The second-order compensation voltage is: A second-order compensation voltage is connected across resistors R4 and R5, generating a second-order compensation current. Therefore, the reference voltage after first-order and second-order compensation is: After second-order compensation, the reference voltage can achieve a temperature drift of ≤1mV.

[0038] Figure 3 As a high-precision reference voltage, the temperature curve after first-order and second-order compensation shows a voltage change of ≤0.4mV from -40℃ to 125℃, which can meet the requirements of high-precision analog-to-digital converters and digital-to-analog converters.

[0039] Figure 4 This is a schematic diagram of a high-precision reference voltage startup circuit. Assuming that the core circuits Q1 and QS1 are not started and there is no current, the gate of MS1 will be pulled to ground potential through resistor RS, thus injecting current into node VA. When the VA voltage exceeds VBE, the core circuit starts up and, through the current mirrors Q1-QS1-MS2-MS3, pulls the gate of MS1 to the power supply, thereby stopping the current injection into node VA and completing the startup process of the reference voltage circuit.

[0040] However, after the startup process is completed, the collector current of Q1 not only provides base current to Q1, but also provides base current to QS1, which causes the collector current of the core circuit BJT to be unbalanced, thus causing the reference voltage to be incorrect.

[0041] In addition, the existing startup circuit injects current directly into the VA node through the power supply via MS1. During startup, because there is no current limiting, the startup current is relatively large, which leads to ringing problems.

[0042] Therefore, the present invention improves upon the prior art, such as... Figure 5 As shown, the high-precision reference voltage start-up circuit of the present invention consists of a start-up current ISTART, a control switch SW1, a current sensor MST, a reference current IREF, a filter circuit, and a comparator circuit CMP1.

[0043] In this embodiment, assuming the high-precision reference voltage circuit is not started, there will be no current in MST. The VN node is pulled to ground by IREF. Through filtering and CMP1, VSC is ensured to be logic high, and SW1 is turned on. ISTART injects current into the VA node through SW1. When the VA node voltage exceeds VBE, the reference circuit starts. Through the current mirror MST, the VN node is pulled to logic high, and after filtering and CMP1, VSC is ensured to be logic high; thus turning off the switch. ISTART no longer injects current into the VA node, thereby completing the startup process of the reference circuit.

[0044] To prevent ringing during startup, a current source is used to control the injection intensity of the current at the VA node; in addition, a filter circuit is used to shape and filter the voltage at the VN node to eliminate high-frequency glitches; and CMP1 is used to further eliminate noise glitches, thereby eliminating ringing.

[0045] In one embodiment, such as Figure 6 The diagram shows an implementation of the high-precision reference voltage startup circuit of this invention. The current mirror is implemented using a single transistor, but a Cascade structure can also be used for mirroring. Switch SW1 uses a transmission gate, but a single transistor can also be used. The filter circuit uses an RC structure, but CRC, LC, or other structures can also be used. Comparator CMP1 is implemented using a hysteresis comparator. CMP1 has two toggling thresholds, VIL and VIH. As long as VIL ≥ VSS + Vnoise and VIH ≤ VDD - Vnoise, it is acceptable. Vnoise is the system noise. As long as VIL and VIH are identifiable, the hysteresis voltage Window = VIH - VIL should be as large as possible.

[0046] In this embodiment, the typical transfer characteristic curve of comparator CMP1 is as follows: Figure 7 As shown, this comparator protects against two toggling thresholds, VIL and VIH. When the input voltage is greater than or equal to VIH, the output logic is high; when the input voltage is less than or equal to VIL, the output logic is low.

[0047] This invention proposes a high-precision reference voltage startup circuit, including a startup current ISTART, a control switch SW1, a current sensor MST, a reference current IREF, a filter circuit, and a comparator circuit. One end of the startup current ISTART is connected to the drain of the current sensor MST, and the other end is connected to the control switch SW1. The output of the control switch SW1 is connected to the VA node. This high-precision reference voltage startup circuit uses a current source to control the injection intensity of the current at the VA node. Furthermore, the filter circuit shapes and filters the voltage at the VN node to eliminate high-frequency glitches. The CMP1 further eliminates noise glitches, thereby eliminating ringing. This solves the error and ringing problems introduced by the reference startup circuit, ensuring that the reference temperature drift is ≤1mV within the temperature range of -40℃ to 125℃, and guaranteeing that there is no ringing problem during the startup process.

[0048] The foregoing description and illustrations have shown and described the basic principles, main features, and advantages of this invention. Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A high-precision reference voltage start-up circuit, characterized in that, It includes a starting current ISTART, a control switch SW1, a current sensor MST, a reference current IREF, a filter circuit, and a comparator circuit. One end of the starting current ISTART is connected to the drain of the current sensor MST, and the other end is connected to the control switch SW1. The output of the control switch SW1 is connected to the VA node. The source of the current sensing MST is connected to the filter circuit and the reference current IREF, with the connection point being the VN node. The gate of the current sensing MST is connected to the output. The "+" input terminal of the comparator circuit is connected to the other end of the filter circuit, the "-" input terminal is connected to the positive terminal of VR, and the output terminal is connected to the control switch SW1. When the circuit starts, the starting current ISTART injects current into the VA node to eliminate the base current error; the filter circuit and comparator circuit control the current injection switch in the starting circuit detection loop to eliminate ringing. Assuming the high-precision reference voltage circuit is not started, there is no current in the current detection MST, and the VN node is pulled to ground potential by the reference current IREF. Through the filter circuit and comparator circuit, VSC is ensured to be logic high, and the control switch SW1 is turned on. The starting current ISTART injects current into node VA through control switch SW1. When the voltage of node VA exceeds VBE, the reference circuit starts. Through current detection MST, node VN is pulled to logic high, and after passing through the filter circuit and comparator circuit, VSC is ensured to be logic high, thereby turning off the switch. The starting current ISTART no longer injects current into the VA node, completing the startup process of the reference circuit.

2. The high-precision reference voltage start-up circuit according to claim 1, characterized in that, The control switch SW1 can be a transmission gate or a single tube.

3. The high-precision reference voltage start-up circuit according to claim 1, characterized in that, The current sensing MST is a current mirror, which can be implemented using a single tube or a Cascade structure.

4. The high-precision reference voltage start-up circuit according to claim 1, characterized in that, The starting current ISTART is a constant current source.

5. The high-precision reference voltage start-up circuit according to claim 1, characterized in that, The filter circuit can adopt a resistor R-capacitor C structure, a capacitor C-resistor R-capacitor C structure, or an inductor L-capacitor C structure.

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