Radiation hardening band-gap reference current source circuit

Abstract

The invention relates to a radiation hardening band-gap reference current source circuit, and belongs to the technical field of radiation resistance of integrated circuits. Over-degradation of the threshold in a high total dose environment is focused on a circuit design level, closed-loop adjustment of the threshold voltage is realized through total dose detection and a dynamic compensation mechanism, and reliability and stability of the circuit in the high dose radiation environment are remarkably improved. Through the embedded logic of the reinforced circuit, the anti-radiation performance of the reinforced circuit is ensured, and the reinforced circuit can work normally in a high-dose environment. Reliable triggering and system self-recovery in a full dose range can be realized through a bias closed-loop design provided by a reference circuit for a reinforced loop, and the application requirements of extreme environments such as spaceflight and nuclear energy are met. The method has the advantages of anti-radiation effect, good dynamic nature, strong transportability and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit radiation-hardening design, and particularly relates to a radiation-hardened bandgap reference current source circuit, especially for the hardening design against the total ionizing dose (TID) effect. Background Art

[0002] In radiation environments such as aerospace and nuclear energy, integrated circuits are vulnerable to radiation effects. Regarding the total ionizing dose effect: in a total dose environment, there will be MOS device threshold voltage degradation, carrier mobility degradation, increased leakage current, etc. In the prior art, the total dose resistance ability is often improved through layout design, material optimization, etc., and the focus is on the hardening of leakage current, but the influence caused by excessive threshold voltage drift still cannot be solved. Therefore, there is an urgent need for a hardening solution that can detect radiation effects in real time and dynamically adjust the threshold to improve the full-dose radiation resistance ability of the circuit.

[0003] The bandgap reference current source provides a reference current that is not affected by PVT (Process-Voltage-Temperature) for the circuit and is widely used in analog modules of circuits such as power management and mixed-signal. Its reliability determines the performance of the entire system. Therefore, in the field of radiation hardening, higher requirements are imposed on the design of the bandgap reference circuit. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention proposes a radiation-hardened bandgap reference current source circuit, which realizes the closed-loop regulation of the threshold voltage through a total dose detection and dynamic compensation mechanism to ensure the functional integrity of the circuit under high-dose radiation.

[0005] To achieve the above invention purpose, the technical solution of the present invention is as follows:

[0006] An anti-radiation hardened bandgap reference current source circuit includes a total dose detection circuit, a hardening circuit, and a bandgap reference circuit. The total dose detection circuit detects the change in the threshold voltage and provides a working signal for the hardening circuit. After the hardening circuit works, it provides a bias for some circuits in the bandgap reference circuit to compensate for the influence of threshold degradation, playing the role of anti-total dose hardening. The total dose detection circuit includes a resistor R and an NMOS transistor NM. The upper end of the resistor R is connected to the power supply VDD, and the lower end is connected to the drain of the NMOS transistor NM. The gate and drain of the NMOS transistor NM are short-circuited, the source is grounded at the ground potential GND, and the substrate is connected to the output terminal VB of the hardening circuit. The drain of the NMOS transistor NM is the output port VDOSE. The hardening circuit includes a comparison circuit, an oscillation circuit, and a negative voltage charge pump circuit. The positive input terminal of the comparison circuit has a reference voltage VREF,DOSE provided by the core reference circuit, and the negative input terminal is the output VDOSE of the total dose detection circuit. The oscillation circuit is controlled by the output of the comparison circuit. When the comparison circuit outputs a high-level signal, the oscillation circuit outputs a high-frequency oscillation signal. When the comparison circuit outputs a low-level signal, the oscillation circuit outputs a low-level signal. The negative voltage charge pump circuit is controlled by the oscillation circuit. When the oscillation circuit outputs an oscillation signal, the negative voltage charge pump circuit outputs a slowly decreasing negative voltage signal. When the oscillation circuit outputs a low-level signal, the output voltage of the negative voltage charge pump is stable and unchanged. The output of the hardening circuit is the output VB of the charge pump circuit. The bandgap reference circuit includes an adaptive startup circuit, a current-mode core circuit, an operational amplifier circuit, and an output circuit, where the current-mode core circuit is implemented by DTMOS. The NMOS substrate of the operational amplifier circuit is connected to the output terminal VB of the hardening circuit. The output circuit generates an output current IREF and generates an additional reference voltage VREF,DOSE to be provided to the hardening circuit.

[0007] The total dose detection circuit and the hardening circuit described above also need to output correct signals at a certain dose to achieve the hardening effect. In the present invention, both the total dose detection circuit and the hardening circuit adopt anti-radiation fault-tolerant designs to ensure that even if some modules fail at high doses, they can still output effective signals to drive the hardening circuit.

[0008] The present invention adopts a hardening method based on the substrate bias effect of MOS transistors, which solves the problem of the failure of the reference circuit caused by excessive degradation of the NMOS threshold voltage at high doses. On the basis that the hardening circuit provides a substrate bias for some devices in the reference circuit, the reference circuit then provides a reference current for the hardening module. This closed-loop design can achieve reliable triggering and system self-recovery within the full dose range.

[0009] In the present invention, all NMOS transistors adopt a ring-gate layout hardening structure to alleviate the leakage problem in the total dose environment.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: It can solve the problem of circuit failure caused by excessive degradation of the NMOS threshold voltage at high doses. It is not limited to this circuit and has strong portability. Description of the Drawings

[0011] Figure 1 It is the overall block diagram of the radiation-hardened bandgap reference current source circuit, showing the connection relationship of the total dose detection circuit, the reinforcement circuit, and the bandgap reference circuit;

[0012] Figure 2 It is the structural diagram of the total dose detection circuit, including the detection loop of resistor R and NMOS transistor NM;

[0013] Figure 3 It is the working flow chart of the reinforcement circuit, showing the cooperative control logic of the comparator, oscillator, and negative voltage charge pump;

[0014] Figure 4 It is the circuit diagram of the bandgap reference circuit, including an adaptive startup circuit, a current-mode core circuit, an operational amplifier circuit, and an output circuit;

[0015] Figure 5 It is the output of the bandgap reference circuit under different radiation doses, and the output reference current before and after reinforcement is compared. Detailed Embodiments

[0016] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0017] As Figure 1 shown, a radiation-hardened bandgap reference current source circuit includes a total dose detection circuit, a reinforcement circuit, and a core reference circuit. The total dose detection circuit detects the change in the threshold voltage and provides a working signal for the reinforcement circuit. After the reinforcement circuit works, it provides a bias for some circuits in the core reference circuit to compensate for the influence of threshold degradation, playing a role in radiation-hardening against total dose.

[0018] As Figure 2 shown, the total dose detection circuit includes resistor R and NMOS transistor NM; the upper end of resistor R is connected to power supply VDD, and the lower end is connected to the drain of NMOS transistor NM; the gate and drain of NMOS transistor NM are short-circuited, the source is grounded to ground potential GND, and the substrate is connected to the output terminal VB of the reinforcement circuit; the drain of NMOS transistor NM is the output port VDOSE.

[0019] As Figure 3As shown, the reinforced circuit includes a comparison circuit, an oscillation circuit, and a negative voltage charge pump circuit;

[0020] The positive input terminal of the comparison circuit is supplied with the reference voltage VREF,DOSE by the core reference circuit, and the negative input terminal is the output VDOSE of the total dose detection circuit;

[0021] The oscillation circuit is controlled by the output of the comparison circuit. When the comparison circuit outputs a high-level signal, the oscillation circuit outputs a high-frequency oscillation signal. When the comparison circuit outputs a low-level signal, the oscillation circuit outputs a low-level signal;

[0022] The negative voltage charge pump circuit is controlled by the oscillation circuit. When the oscillation circuit outputs an oscillation signal, the negative voltage charge pump circuit outputs a negative voltage signal that slowly decreases. When the oscillation circuit outputs a low-level signal, the negative voltage charge pump stably outputs a constant voltage. The output of the reinforced circuit is the output VB of the charge pump circuit.

[0023] The core reference circuit includes an adaptive startup circuit, a current-mode core circuit, an operational amplifier circuit, and an output circuit, where the current-mode core circuit is implemented by DTMOS; the NMOS substrate of the operational amplifier circuit is connected to the output terminal VB of the reinforced circuit; the output circuit generates an output current IREF and generates an additional reference voltage VREF,DOSE to be supplied to the reinforced circuit.

[0024] As Figure 4As shown, the core reference circuit includes: capacitor C0, resistors R0, R1, R2, R3, PMOS transistors PM0, PM1, PM2, PM3, PM4, PM5, PM6, PM7, PM8, PM9, PM10, PM11, PM12, PM13, PM14, PM15, PM16, PM17, PM18 and PM19, NMOS transistors NM0, NM1, NM2, NM3, NM4, NM5, NM6, NM7 and NM8, and DTMOS transistors MA and MB; the substrates of all PMOS are shorted to the source terminals, among which the source terminals of PM0, PM1, PM2, PM3, PM4, PM6, PM8, PM10, PM12, PM16, PM18 are connected to the power supply VDD; the substrates of NM0, NM1, NM2 are shorted to the source terminals and grounded to the ground terminal VSS; the substrates of NM3, NM4, NM6, NM7, NM8 are connected to the output terminal VB of the reinforcement circuit; the substrate of NM5 is grounded, and the source terminal is connected to the drain terminal of NM6, and the gate and drain of NM6 are shorted; the gate of PM0 is connected to the gate of NM0 and grounded to the ground terminal VSS; the drain of PM0 is connected to the drain of NM0 and at the same time connected to the gate of PM1, the drain of NM1, and the gate of NM2; the drain of PM1 is connected to the drain of NM2 and at the same time connected to the gate of PM2; the drain of PM2 is connected to the upper plate of capacitor C0 and the gates of NM3 and NM4; the gate and drain of PM3 are shorted and connected to the gates of PM3, PM5, PM7, PM9, PM11, PM13, PM17, PM19, and at the same time connected to the drain of NM3; the gate of PM4 is connected to the drain of PM5 and connected to the gates of PM6, PM8, PM10, PM12, PM17, PM18, and at the same time connected to the drain of NM4; the drain of PM4 is connected to the source of PM5; the drain of PM6 is connected to the source of PM7; the gate and drain of NM5 are shorted and connected to the drain of PM7 and the gate of NM1; the gate and drain of NM6 are shorted and connected to the source of PM5; the drain of PM8 is connected to the source of PM9, and the drain of PM9 is connected to the upper ends of resistor R1 and R0 and the gate of PM15; the lower end of R0 is connected to the source of MA, and the lower end of R1 is grounded to VSS; the drain of PM10 is connected to the source of PM11, and the drain of PM11 is connected to the upper end of resistor R2, the source of MB, and the gate of PM14; the lower end of R2 is grounded to the ground terminal VSS; the substrates and drains of MA and MB are shorted and both are grounded to the ground terminal VSS; the drain of PM12 is connected to the source of PM13, and the drain of PM13 is connected to the sources of PM14 and PM15; the drain of PM14 is connected to the drain and gate of NM7 and the gate of NM8; the drain of PM15 is connected to the drain of NM8 and connected to the gates of NM4 and NM3; the drain of PM16 is connected to the source of PM17, and the drain of PM17 is the output port of the reference current IREF;The drain terminal of PM16 is connected to the source terminal of PM19. The drain terminal of PM19 is connected to the upper end of resistor R3 and serves as VREF. DOSE is connected to the positive input terminal of the comparison circuit in the radiation-hardened circuit.

[0025] Embodiment 1: Circuit Connection and Working Process

[0026] This embodiment details the connection method and working process of a radiation-hardened bandgap reference current source circuit. The specific steps are as follows:

[0027] 1. Total Dose Detection Circuit: The total dose detection circuit consists of resistor R and NMOS transistor NM. Its core function is to detect the change in the threshold voltage with the total dose. Therefore, the output voltage of the detection circuit needs to accurately track the change of V th That is, it changes monotonically with V th The current of the detection circuit is jointly defined by the detection NMOS transistor NM and resistor R. The final output voltage is:

[0028]

[0029] Among them, V dose is the output voltage of the detection circuit, V dd is the power supply voltage, V th is the threshold voltage of the MOS transistor, K is the process parameter of the MOS transistor, and R is the resistor in the total dose detection circuit. The monotonicity of this voltage with respect to the threshold change is:

[0030]

[0031] In the actual circuit, V th < V dd Obviously, it always holds. So, > 2, then the above formula is always positive, and the detection voltage will decrease as the threshold voltage decreases. Therefore, in the total dose environment, as the dose increases, the detection voltage will decrease to reflect the decrease in the threshold voltage. Although it cannot correspond exactly in a 1:1 ratio, it can still play a detection role.

[0032] 2. Reinforcement Circuit: The reinforcement circuit includes a comparator, an oscillator, and a negative voltage charge pump, which are used to dynamically compensate for the threshold voltage degradation. The positive input terminal of the comparator is connected to the reference voltage VREF,DOSE generated by the core reference circuit, and the negative input terminal is connected to the output VDOSE of the total dose detection circuit. When VDOSE is lower than VREF,DOSE, the comparator outputs a high-level signal to trigger the oscillator to work. The oscillator adopts a ring oscillator structure and is composed of multiple cascaded inverters. When the comparator outputs a high level, the oscillator outputs a high-frequency clock signal to drive the negative voltage charge pump to work. The negative voltage charge pump is composed of diodes and capacitors and generates a negative voltage VB according to the clock signal output by the oscillator. This negative voltage signal is fed back to the substrate of the NMOS transistor, and the threshold voltage degradation is compensated through the body effect formula, enabling the NMOS transistor to re-enter the correct working state and restoring the circuit function:

[0033]

[0034] where V th0 is the threshold voltage when the source-substrate voltage is 0, γ is related to the body effect coefficient and doping concentration, etc., φ p is the substrate Fermi potential, and Vsb is the source-substrate potential difference.

[0035] 3. Core Reference Circuit: The core reference circuit includes an adaptive startup circuit, a current-mode core circuit, and an operational amplifier circuit; the adaptive startup circuit is used to ensure that the circuit quickly enters a stable working state when powered on, avoiding current fluctuations during the startup process; the current-mode core circuit is implemented using DTMOS (Dynamic Threshold MOS), replacing the traditional BJT structure, avoiding the increase in base current and decrease in current gain of the BJT under total dose conditions; the NMOS substrate of the operational amplifier circuit is connected to the output terminal of the reinforcement circuit to receive the dynamically generated negative voltage bias signal to compensate for the threshold voltage degradation caused by radiation.

[0036] Example 2: Radiation Tolerant and Fault Tolerant Mechanism of the Reinforcement Circuit

[0037] This example details the fault tolerance mechanism of the reinforcement circuit in a high-dose radiation environment to ensure the reliability of the circuit under extreme conditions:

[0038] 1. Fault Tolerance Design of Comparator: The comparator adopts a three-stage cascaded structure with a hysteresis window to ensure that even if some modules fail under high-dose radiation, it can still output an effective signal to drive the hardened circuit. When the radiation dose exceeds the set threshold, the comparator forcibly outputs a high-level signal to ensure that the hardened circuit remains activated. The positive input terminal of the comparator is biased by the reference circuit. Under high-dose conditions, the reference voltage will have a positive offset. However, when it serves as the signal of the non-inverting input terminal of the comparator, the offset direction is consistent with the logical direction of the threshold decrease, still ensuring that the comparator outputs the correct logical state. At the same time, the recovery of the threshold voltage during the hardening process can ensure that before the detection voltage VDOSE returns to the set value, the reference voltage VREF,DOSE has returned to the normal range through hardening, avoiding interference with the turn-off function of the hardened circuit.

[0039] 2. Radiation Resistance Optimization of Oscillator: The oscillator adopts a PMOS pull-up enhanced inverter to avoid lock-up failures caused by the negative threshold shift of NMOS. Under high-dose radiation, the oscillation frequency of the oscillator is adaptively adjusted according to the radiation dose to ensure that the output rate of the negative voltage charge pump matches the threshold degradation rate.

[0040] 3. Reliability Improvement of Negative Voltage Charge Pump: The negative voltage charge pump uses a diode structure to replace the traditional MOS switch to improve the radiation resistance. By optimizing the ratio of the charging capacitor to the load capacitor, the stability and response speed of the negative voltage signal are ensured.

[0041] Example 3: Circuit Performance Verification

[0042] In this example, the radiation resistance performance of the circuit is verified through simulation and experiment:

[0043] The threshold degradation at different doses is calibrated using the tape-out results. Due to the large threshold drift in this process, the unhardened circuit fails at 70 krad, while the hardened circuit can still work normally at 100 krad. At a radiation dose of 100 krad, the hardened circuit restores the reference current to the set value. In the temperature range from -40°C to 125°C, the output deviation is less than 2%, and it can be further calibrated by trimming the resistor.

[0044] Working Principle:

[0045] The main working principle is as follows: When VDOSE > VREF,DOSE, the hardened circuit does not work; when VDOSE < VREF,DOSE, the comparator outputs a high signal, which serves as the enable signal for the next-stage oscillator. The oscillator outputs a high-frequency clock signal to supply the charge pump to generate a negative voltage, which is fed back to the NMOS substrate to raise the threshold voltage using the body effect. After raising to the hysteresis window set in the circuit, the comparator will output a low signal again, and the voltage boosting stops.

[0046] In summary, the present invention proposes a radiation-hardened bandgap reference current source circuit, which focuses on the over-degradation of the threshold in a high total dose environment at the circuit design level. Through the total dose detection and dynamic compensation mechanism, the closed-loop regulation of the threshold voltage is achieved, significantly improving the reliability and stability of the circuit in a high-dose radiation environment. By embedding logic in the hardened circuit, the radiation resistance performance of the hardened circuit itself is ensured, and it can also work normally in a high-dose environment. The present invention has the advantages of anti-radiation effect, good dynamic performance, strong portability, etc.

Claims

1. A radiation hardened bandgap reference current source circuit, characterized in that: It includes a total dose detection circuit, a reinforcement circuit and a core reference circuit. The total dose detection circuit detects changes in the threshold voltage and provides a working signal for the reinforcement circuit. After the reinforcement circuit works, it provides bias for some circuits in the core reference circuit to compensate for the impact of threshold degradation and play a role in anti-total dose reinforcement.

2. The radiation hardened bandgap reference current source circuit according to claim 1, characterized in that: The total dose detection circuit includes a resistor R and an NMOS tube NM; the upper end of the resistor R is connected to a power supply VDD, and the lower end is connected to a drain end of the NMOS tube NM; the gate end and the drain end of the NMOS tube NM are short-circuited, the source end is grounded to a potential GND, and the substrate is connected to an output end VB of the reinforcement circuit; the drain end of the NMOS tube NM is an output port VDOSE.

3. The radiation hardened bandgap reference current source circuit according to claim 1, characterized in that: The reinforcement circuit includes a comparison circuit, an oscillation circuit, and a negative pressure charge pump circuit; The reference voltage VREF,DOSE at the positive input of the comparison circuit is provided by the core reference circuit, and the negative input is the output VDOSE of the total dose detection circuit; The oscillation circuit is controlled by the output of the comparison circuit. When the comparison circuit outputs a high-level signal, the oscillation circuit outputs a high-frequency oscillation signal. When the comparison circuit outputs a low-level signal, the oscillation circuit outputs a low-level signal. The negative voltage charge pump circuit is controlled by the oscillation circuit. When the oscillation circuit outputs an oscillation signal, the negative voltage charge pump circuit outputs a slowly decreasing negative voltage signal. When the oscillation circuit outputs a low level signal, the negative voltage charge pump outputs a stable voltage unchanged. The output of the reinforcement circuit is the output VB of the charge pump circuit.

4. The radiation hardened bandgap reference current source circuit according to claim 1, characterized in that: The core reference circuit includes an adaptive startup circuit, a current mode core circuit, an operational amplifier circuit, and an output circuit, wherein the current mode core circuit is implemented by DTMOS; the NMOS substrate of the operational amplifier circuit is connected to the output terminal VB of the reinforcement circuit; the output circuit generates an output current IREF and generates an additional reference voltage VREF, DOSE to provide to the reinforcement circuit.

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