Protection circuit and band-gap reference circuit

Abstract

The invention discloses a protection circuit and a band-gap reference circuit, the protection circuit is used for a to-be-protected circuit, the to-be-protected circuit comprises an input stage unit and an output stage unit, the output stage unit comprises a weak driving module, an auxiliary module and an output module, and the protection circuit comprises a first protection unit and a second protection unit. According to the protection circuit and the band-gap reference circuit, when the power supply generates negative noise interference, the first protection unit cuts off the path between the input stage unit and the power supply voltage, so that the power supply voltage of the input stage unit is maintained to be higher than the lowest working voltage required by the input stage unit in a short time; the input stage unit is ensured to be in a normal working state; for an output stage unit with an intermediate filtering node, the weak driving node is helped to be established to a correct level more quickly in the recovery process of the power supply voltage in a mode of locking the weak driving node charge by using a second protection unit.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit technology, specifically relating to a protection circuit and a bandgap reference circuit. Background Technology

[0002] In modern electronic devices, the integrity of the power network is the cornerstone of the stable operation of the entire system. However, the power signals in real-world applications are far from ideal DC, and various complex noise interferences are superimposed on them. These power noises have become key factors affecting the performance and reliability of the equipment.

[0003] Power supply noise mainly originates from the following two aspects:

[0004] External conducted interference: Noise introduced into the device from the external power grid through the power port, including surges, voltage dips, and electromagnetic interference from other devices.

[0005] Internal interference: generated by the operation of the equipment's own circuits, mainly including: (a) transient large current (ΔI / Δt) caused by the switching action of digital integrated circuits, which generates a voltage drop (IR Drop) on the parasitic impedance of the power distribution network; (b) the switching frequency of the high-frequency switching power supply and its harmonics; (c) coupling interference between various circuit modules through the power path (common impedance coupling).

[0006] These power supply noises can cause malfunctions in the logic of electronic devices, such as timing errors in digital circuits, data loss, and microcontroller crashes. They can also degrade signal integrity, worsening the performance of analog front-ends (AFEs) or mixed-signal circuits, such as reducing the signal-to-noise ratio (SNR), increasing measurement errors, and leading to a decrease in audio / video quality. More seriously, they can reduce system reliability, as continuous high-frequency noise can accelerate component wear and cause permanent hardware damage such as component breakdown.

[0007] To improve the circuit's immunity to power supply noise, large capacitors and resistors are typically added to the power input port during the design phase to ensure the correctness of the chip's signals. Adding large capacitors and resistors to the power input port can significantly improve the chip's immunity to power supply noise. However, to meet the circuit's power consumption requirements, it's not feasible to connect a large resistor in series in the filtering circuit. Therefore, a very large capacitor area is usually required, significantly increasing the chip's cost.

[0008] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to provide a protection circuit and a bandgap reference circuit that can reduce chip area and cost while resisting power supply noise interference.

[0010] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution: a protection circuit for a circuit to be protected, the circuit to be protected including an input stage unit and an output stage unit, the protection circuit including a first protection unit and a second protection unit, the first protection unit being connected between the input stage unit and the power supply voltage to cut off the path between the input stage unit and the power supply voltage when the power supply voltage changes.

[0011] The output stage unit includes a weak drive module, an auxiliary module, and an output module. The input terminal of the weak drive module is connected to the output terminal of the input stage unit, and the output terminal of the weak drive module is connected to the input terminal of the output module. The weak drive module outputs a drive signal based on the first characterization signal output by the input stage unit. The output module is powered by the power supply voltage and generates a second characterization signal based on the control of the drive signal.

[0012] The second protection unit and the auxiliary module are connected in series between the output terminal of the weak drive module and the power supply voltage. The auxiliary module is also connected to the input terminal of the weak drive module and the output terminal of the input stage unit. The auxiliary module is used to improve the driving capability of the drive signal based on the control of the first characterization signal. The second protection unit is also connected to the output terminal of the output module to control the on / off state of the branch between the output terminal of the weak drive module and the auxiliary module based on the second characterization signal.

[0013] In one or more embodiments of the present invention, the first protection unit includes: a first response control module, a switching unit, and a second response control unit. The first response control module is connected to a power supply voltage to be turned on based on the control of the power supply voltage. The first response control module is connected to the control terminal of the switching unit to control the switching unit to be turned on based on its own turn-on. The second terminal of the switching unit is connected to the power supply voltage, and the first terminal of the switching unit is connected to an input stage unit. The second response control unit is connected to the power supply voltage, the control terminal of the switching unit, and the first terminal of the switching unit. The second response control unit controls the voltage between the control terminal of the switching unit and the first terminal of the switching unit based on the power supply voltage.

[0014] In one or more embodiments of the present invention, the switching unit includes a first transistor, the control terminal of the first transistor is connected to a first response control module, the second terminal of the first transistor is connected to a power supply voltage, and the first terminal of the first transistor is connected to an input stage unit.

[0015] In one or more embodiments of the present invention, the first response control module includes a response unit and a first transistor. The response unit is connected to a power supply voltage to generate a control voltage that varies with the power supply voltage. The control terminal of the first transistor is connected to the response unit to receive the control voltage. A first terminal of the first transistor is connected to a reference voltage. A second terminal of the first transistor is connected to the control terminal of a switching unit to turn on the switching unit when the first transistor is turned on.

[0016] In one or more embodiments of the present invention, the response unit includes a first resistor and a first capacitor, a first terminal of the first resistor is connected to a power supply voltage, a second terminal of the first resistor is connected to a first terminal of the first capacitor and a control terminal of a first transistor, and a second terminal of the first capacitor is connected to a reference voltage.

[0017] In one or more embodiments of the present invention, the second response control unit includes a second transistor, the second terminal of the second transistor is connected to the control terminal of the switching unit, the first terminal of the second transistor is connected to the first terminal of the switching unit, and the control terminal of the second transistor is connected to the power supply voltage.

[0018] In one or more embodiments of the present invention, the first protection unit further includes an interlocking unit, which is connected to the power supply voltage, the first response control module, and the control terminal of the switching unit. The first response control module is used to control the interlocking unit to open based on the power supply voltage, and the interlocking unit maintains the opening of the first response control module based on its own opening.

[0019] In one or more embodiments of the present invention, the interlocking unit includes a third transistor, the first terminal of the third transistor is connected to the power supply voltage, the control terminal of the third transistor is connected to the control terminal of the switching unit and the first response control module, the second terminal of the third transistor is connected to the first response control module, and the third transistor is used to pull up the control voltage inside the first response control module when it is turned on to maintain the first response control module being turned on.

[0020] In one or more embodiments of the present invention, the second protection unit includes a second switch transistor, the control terminal of the second switch transistor is connected to the output terminal of the output module, the first terminal of the second switch transistor is connected to the output terminal of the weak drive module, and the second terminal of the second switch transistor is connected to the auxiliary module.

[0021] The present invention also discloses a bandgap reference circuit, including the protection circuit. The bandgap reference circuit further includes an input stage unit and an output stage unit. The input stage unit includes a BG module and a signal generation circuit. The first protection unit is connected between the BG module and the power supply voltage to cut off the path between the BG module and the power supply voltage when the power supply voltage changes. The signal generation circuit is connected to the BG module to generate a first characterization signal for characterizing whether the BG module is established.

[0022] The output stage unit includes a weak drive module, an auxiliary module, and an output module. The weak drive module includes a first inverter and a filter unit. The input terminal of the first inverter is connected to the output terminal of the input stage unit. The filter unit is located at the output terminal of the first inverter to filter the signal output by the first inverter and generate a drive signal.

[0023] The second protection unit and the auxiliary module are connected in series between the output terminal of the filter unit and the power supply voltage. The auxiliary module is also connected to the input terminal of the first inverter. The auxiliary module is used to improve the driving capability of the drive signal based on the control of the first characterization signal. The output module is powered by the power supply voltage and generates a second characterization signal based on the control of the drive signal. The second protection unit is also connected to the output terminal of the output module to control the on / off state of the branch between the output terminal of the filter unit and the auxiliary module based on the second characterization signal.

[0024] Compared with the prior art, the protection circuit and bandgap reference circuit of the present invention, when the power supply is subjected to negative noise interference, cut off the path between the input stage unit and the power supply voltage through the first protection unit, thereby maintaining the power supply voltage of the input stage unit higher than the minimum operating voltage required by the input stage unit for a short time, ensuring that the input stage unit is in normal working condition; for the output stage unit with intermediate filter nodes, the second protection unit locks the charge of the weak drive node, helping the weak drive node to establish to the correct level more quickly during the power supply voltage recovery process. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a circuit diagram of a bandgap reference circuit according to an embodiment of the present invention.

[0027] Figure 2This is a schematic diagram of the node waveforms of an output stage unit that does not have a second protection circuit and auxiliary circuit in the prior art.

[0028] Figure 3 This is a schematic diagram of the node waveforms of an output stage unit equipped with a second protection circuit and an auxiliary circuit in one embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the node waveforms of the input stage unit and the output stage unit in the prior art that do not have a first protection circuit.

[0030] Figure 5 This is a schematic diagram of the node waveforms of a first protection circuit, a second protection circuit, and an auxiliary circuit in one embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0032] The terms "coupled," "connected," or "linked" in the specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as an electrical conduction medium, which may have parasitic inductance or capacitance. Indirect connections may also include connections made through other active or passive devices to achieve the same or similar functional purpose, such as connections through switches, follower circuits, or other circuits or components. Furthermore, in the invention, terms such as "first" and "second" are primarily used to distinguish one technical feature from another, and do not necessarily require or imply any actual relationship, quantity, or order between these technical features.

[0033] In the detailed description of this specification, reference is made to the accompanying drawings, which form a part thereof, wherein like reference numerals always denote like parts, and wherein exemplary embodiments are shown by way of example that may be implemented. It should be understood that other embodiments may be utilized, and structural or logical changes may be made, without departing from the scope of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0034] The various operations in the specification may be described sequentially as multiple discrete actions or operations in a manner most conducive to understanding the claimed subject matter. However, the order of description should not be construed as implying that these operations must be sequentially related. Specifically, these operations may not be performed in the order presented. The described operations may be performed in a different order than in the described embodiments. Various additional operations may be performed in additional embodiments and / or the described operations may be omitted.

[0035] For the purposes of this disclosure, the phrase “A and / or B” means (A), (B), or (A and B). For the purposes of this disclosure, the phrase “A, B and / or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0036] Various components and devices may be referred to or shown in the singular (e.g., “transistor”, “transistor”, “switch”, etc.) in this document, but only for the convenience of discussion, and any element referred to in the singular may include multiple such elements as taught herein.

[0037] The description uses the phrases "in one embodiment," "in other embodiments," or "in some embodiments," each of which may refer to one or more of the same or different embodiments. Furthermore, the terms "comprising," "including," "having," etc., used with respect to embodiments of this disclosure are synonymous.

[0038] One embodiment of the present invention provides a protection circuit for a circuit to be protected. The circuit to be protected can be a circuit with different structures, including an input stage unit and an output stage unit.

[0039] The output stage unit includes a weak drive module, an auxiliary module, and an output module. The input terminal of the weak drive module is connected to the output terminal of the input stage unit, and the output terminal of the weak drive module is connected to the input terminal of the output module. The weak drive module outputs a drive signal based on the first characterization signal output by the input stage unit. The output module is powered by the power supply voltage and generates a second characterization signal based on the control of the drive signal. The auxiliary module is connected to the input terminal of the weak drive module, the output terminal of the weak drive module, and the output terminal of the input stage unit. The auxiliary module is used to improve the driving capability of the drive signal based on the control of the first characterization signal.

[0040] In one embodiment, the weak drive module has a weak drive node, which can be generated by an internal filtering unit. The auxiliary module can pull up the weak drive node to improve the driving capability of the drive signal on the weak drive node.

[0041] The protection circuit includes a first protection unit and a second protection unit. The first protection unit is connected between the input stage unit and the power supply voltage to cut off the path between the input stage unit and the power supply voltage when the power supply voltage changes. The second protection unit and the auxiliary module are connected in series between the output terminal of the weak drive module and the power supply voltage. The second protection unit is also connected to the output terminal of the output module to control the on / off state of the branch between the output terminal of the weak drive module and the auxiliary module based on the second characterization signal.

[0042] In one embodiment, such as Figure 1 As shown, taking the bandgap reference circuit as an example, the input stage of the bandgap reference circuit includes a BG module and a signal generation circuit 20; the output stage includes a weak drive module, an auxiliary module, and an output module. The signal generation circuit 20, the weak drive module, the auxiliary module, and the output module also constitute the BG_OK generation circuit. In other embodiments, the BG module can be other low-power analog circuits, and the signal generation circuit 20, the weak drive module, the auxiliary module, and the output module can be any logic circuit with filtering nodes or weak drive nodes.

[0043] The first protection unit is connected between the BG module and the power supply voltage AVCC to cut off the path between the BG module and the power supply voltage AVCC when the power supply voltage AVCC changes, thereby preventing the BG module from being affected by the power supply voltage AVCC change. The signal generation circuit 20 is connected to the BG module to generate a first characterization signal BG_PRE to characterize whether the BG module has established an output reference voltage. In one embodiment, when the BG module establishes an output reference voltage, the signal generation circuit 20 outputs the first characterization signal BG_PRE based on the control of the reference voltage.

[0044] like Figure 1 As shown, the first protection unit includes: a first response control module 11, a switching unit, a second response control unit 12, and an interlocking unit 13. The switching unit includes a first switching transistor MK1; in other embodiments, the switching unit may be a circuit with other structures.

[0045] The first response control module 11 is connected to the power supply voltage AVCC to turn on based on the control of the power supply voltage AVCC. The first response control module 11 is connected to the control terminal of the first switching transistor MK1 of the switching unit to control the first switching transistor MK1 to turn on based on its own turn-on. The second terminal of the first switching transistor MK1 of the switching unit is connected to the power supply voltage AVCC. The first terminal of the first switching transistor MK1 of the switching unit is connected to the BG module of the input stage unit. When the first switching transistor MK1 is turned on, the BG module of the input stage unit is powered by the power supply voltage AVCC.

[0046] The second response control unit 12 is connected to the power supply voltage AVCC, the control terminal of the first switch transistor MK1 of the switching unit, and the first terminal of the first switch transistor MK1 of the switching unit. The second response control unit 12 controls the voltage between the control terminal of the first switch transistor MK1 and the first terminal of the first switch transistor MK1 based on the power supply voltage AVCC. When the second response control unit 12 is turned on, the first switch transistor MK1 is turned off.

[0047] like Figure 1 As shown, the first response control module 11 includes a response unit and a first transistor M1. The response unit is connected to the power supply voltage AVCC to generate a control voltage that varies with the power supply voltage AVCC. The control terminal of the first transistor M1 is connected to the response unit to receive the control voltage. The first terminal of the first transistor M1 is connected to a reference voltage, and the second terminal of the first transistor M1 is connected to the control terminal of the first switching transistor MK1 to turn on the first switching transistor MK1 when the first transistor M1 is turned on. In one embodiment, the reference voltage is ground voltage.

[0048] The response unit includes a first resistor R1 and a first capacitor C1. The first end of the first resistor R1 is connected to the power supply voltage AVCC. The second end of the first resistor R1 is connected to the first end of the first capacitor C1 and the control terminal of the first transistor M1. The second end of the first capacitor C1 is connected to the reference voltage.

[0049] The second response control unit 12 includes a second transistor M2. The second terminal of the second transistor M2 is connected to the control terminal of the first switching transistor MK1, the first terminal of the second transistor M2 is connected to the first terminal of the first switching transistor MK1, and the control terminal of the second transistor M2 is connected to the power supply voltage AVCC.

[0050] like Figure 1 As shown, the interlock unit 13 is connected to the power supply voltage AVCC, the first response control module 11, and the control terminal of the first switching transistor. The first response control module 11 is used to control the interlock unit 13 to open based on the power supply voltage AVCC, and the interlock unit 13 maintains the opening of the first response control module 11 based on its own opening.

[0051] In one embodiment, the interlocking unit 13 includes a third transistor M3. The first terminal of the third transistor M3 is connected to the power supply voltage AVCC. The control terminal of the third transistor M3 is connected to the control terminal of the first switching transistor MK1 and the second terminal of the first transistor M1 of the first response control module 11. The second terminal of the third transistor M3 is connected to the control terminal of the first transistor M1 of the first response control module 11. The third transistor M3 is used to pull up the control voltage at the control terminal of the first transistor M1 of the first response control module 11 when it is turned on, so as to maintain the first response control module 11 being turned on.

[0052] like Figure 1 As shown, the signal generation circuit 20 includes a fourth transistor M4, a second resistor R2, and a Schmitt trigger N. The control terminal of the fourth transistor M4 is connected to the BG module, the second terminal of the fourth transistor M4 is connected to the first terminal of the second resistor R2 and the input terminal of the Schmitt trigger N, the second terminal of the second resistor R2 is connected to the power supply voltage AVCC, the first terminal of the fourth transistor M4 is connected to the reference voltage, and the output terminal of the Schmitt trigger N is connected to the input terminal of the weak drive module of the output stage unit. When the BG module establishes the output reference voltage, the fourth transistor M4, based on the control of the reference voltage, pulls down the voltage at the input terminal of the Schmitt trigger N to generate the first characterization signal BG_PRE through the Schmitt trigger N. In other embodiments, the Schmitt trigger N may not be included.

[0053] like Figure 1 As shown, the weak drive module includes a first inverter and a filtering unit. The input terminal of the first inverter is connected to the output terminal of the Schmitt trigger N of the input stage unit. The filtering unit is located at the output terminal of the first inverter to filter the signal output by the first inverter to generate a drive signal. In other embodiments, the first inverter can be a conversion circuit with other structures.

[0054] In one embodiment, the first inverter includes a fifth transistor M5 and a sixth transistor M6. The control terminals of the fifth transistor M5 and the sixth transistor M6 are connected to the output terminal of the Schmitt trigger N of the signal generation circuit 20. The first terminal of the fifth transistor M5 is connected to the power supply voltage AVCC, the first terminal of the sixth transistor M6 is connected to a reference voltage, and the second terminals of the fifth transistor M5 and the second terminals of the sixth transistor M6 are connected to a filtering unit. In one embodiment, the filtering unit is an RC filtering unit.

[0055] The filter unit includes a third resistor R3 and a second capacitor C2. The first end of the third resistor R3 is connected to the second end of the fifth transistor M5 of the first inverter. The second end of the third resistor R3 is connected to the second end of the sixth transistor M6 of the first inverter and the first end of the second capacitor C2. The second end of the second capacitor C2 is connected to the reference voltage.

[0056] In one embodiment, the second protection unit 30 and the auxiliary module are connected in series between the output terminal of the filter unit and the power supply voltage AVCC. The auxiliary module is also connected to the input terminal of the first inverter. The auxiliary module is used to improve the driving capability of the drive signal based on the control of the first characterization signal BG_PRE. The output module is powered by the power supply voltage AVCC and generates a second characterization signal based on the control of the drive signal. The second protection unit 30 is also connected to the output terminal of the output module to control the on / off state of the branch between the output terminal of the filter unit and the auxiliary module based on the second characterization signal.

[0057] like Figure 1 As shown, the auxiliary module includes a seventh transistor M7. The first terminal of the seventh transistor M7 is connected to the power supply voltage AVCC, the control terminal of the seventh transistor M7 is connected to the control terminal of the fifth transistor M5 of the first inverter, and the second terminal of the seventh transistor M7 is connected to the output terminal of the filter unit through the second protection unit 30. In other embodiments, the positions of the auxiliary module and the second protection unit 30 can be interchanged.

[0058] like Figure 1 As shown, the second protection unit 30 includes a second switch MK2. The control terminal of the second switch MK2 is connected to the output terminal of the output module to receive the second characterization signal BG_OK. The first terminal of the second switch MK2 is connected to the first terminal of the second capacitor C2 of the weak drive module. The second terminal of the second switch MK2 is connected to the second terminal of the seventh transistor M7 of the auxiliary module.

[0059] The output module includes a third inverter and a fourth inverter connected together. The input of the third inverter is connected to the output of the filter unit to receive the drive signal. The input of the fourth inverter is connected to the output of the third inverter, and the output of the fourth inverter is connected to the control terminal of the second switch MK2 of the second protection unit 30. The output of the fourth inverter is used to output the second characterization signal BG_OK. Both the third and fourth inverters are powered by the power supply voltage AVCC. In other embodiments, the output module can be a shaping circuit with other structures.

[0060] The third inverter includes an eighth transistor M8 and a ninth transistor M9. The first terminal of the eighth transistor M8 is connected to the power supply voltage AVCC. The control terminals of the eighth transistor M8 and the ninth transistor M9 are connected to the first terminal of the second capacitor C2 of the filter unit. The second terminal of the eighth transistor M8 is connected to the second terminal of the ninth transistor M9. The first terminal of the ninth transistor M9 is connected to the reference voltage.

[0061] The fourth inverter includes a tenth transistor M10 and an eleventh transistor M11. The first terminal of the tenth transistor M10 is connected to the power supply voltage AVCC, and the first terminal of the eleventh transistor M11 is connected to the reference voltage. The control terminals of the tenth transistor M10 and the eleventh transistor M11 are connected to the second terminal of the eighth transistor M8. The second terminal of the tenth transistor M10 is connected to the second terminal of the eleventh transistor M11 to output the second characterization signal BG_OK.

[0062] The first transistor M1, the fourth transistor M4, the sixth transistor M6, the second switch MK2, the ninth transistor M9, and the eleventh transistor M11 are N-channel MOSFETs. The first switch MK1, the second transistor M2, the third transistor M3, the fifth transistor M5, the seventh transistor M7, the eighth transistor M8, and the tenth transistor M10 are P-channel MOSFETs. In other embodiments, the first transistor M1, the fourth transistor M4, the sixth transistor M6, the second switch MK2, the ninth transistor M9, and the eleventh transistor M11 are P-channel MOSFETs. The first switch MK1, the second transistor M2, the third transistor M3, the fifth transistor M5, the seventh transistor M7, the eighth transistor M8, and the tenth transistor M10 are N-channel MOSFETs.

[0063] The first terminal of the first transistor M1, the first terminal of the first switch MK1, the first terminal of the second transistor M2, the first terminal of the third transistor M3, the first terminal of the fourth transistor M4, the first terminal of the fifth transistor M5, the first terminal of the sixth transistor M6, the first terminal of the seventh transistor M7, the first terminal of the second switch MK2, the first terminal of the eighth transistor M8, the first terminal of the ninth transistor M9, the first terminal of the tenth transistor M10, and the first terminal of the eleventh transistor M11 are the sources; the second terminal of the first transistor M1, the second terminal of the first switch MK1, the second terminal of the second transistor M2, the second terminal of the third transistor M3, the second terminal of the fourth transistor M4, the second terminal of the fifth transistor M5, and the first terminal of the sixth transistor M6 are the sources. The second terminal of the seventh transistor M7, the second terminal of the second switch MK2, the second terminal of the eighth transistor M8, the second terminal of the ninth transistor M9, the second terminal of the tenth transistor M10, and the second terminal of the eleventh transistor M11 are the drains; the control terminals of the first transistor M1, the first switch MK1, the second transistor M2, the third transistor M3, the fourth transistor M4, the fifth transistor M5, the sixth transistor M6, the seventh transistor M7, the second switch MK2, the eighth transistor M8, the ninth transistor M9, the tenth transistor M10, and the eleventh transistor M11 are the gates.

[0064] The first protection unit is suitable for use in some low-power analog circuits. When the power supply voltage AVCC is interrupted and changes, the first protection unit can maintain the normal operation of the low-power analog circuit for a short time. The second protection unit is suitable for logic circuits with intermediate filtering nodes (such as the weak drive circuit in this embodiment, which has an intermediate filtering node because it is equipped with a filtering unit, i.e., the output terminal of the filtering unit).

[0065] In one embodiment, when the power supply voltage AVCC is established, the control voltage at the control terminal of the first transistor M1 gradually rises under the response of the response unit. After reaching a certain voltage, the first transistor M1 is turned on. At this time, the voltages at the control terminals of the first switch transistor MK1 and the third transistor M3 are pulled down, and the first switch transistor MK1 and the third transistor M3 are turned on. At the same time, the turning on of the third transistor M3 further pulls the control voltage at the control terminal of the first transistor M1 up to the power supply voltage AVCC, strengthening the driving capability of the control terminal of the first transistor M1. The third transistor M3 and the first transistor M1 form a positive feedback interlock. The first switch transistor MK1, as a driving transistor, supplies power to the BG module when it is turned on.

[0066] When positive noise interference occurs in the power supply voltage AVCC (AVCC jumps upward), the control voltage at the control terminal of the first transistor M1 is pulled up to a high level by the first resistor R1. The first switch MK1 and the third transistor M3 remain in the on state, and this will not affect the normal operation of the BG module. In other embodiments, the path between the BG module and the power supply voltage AVCC can also be cut off when positive noise interference occurs in the power supply voltage AVCC.

[0067] When negative noise interference occurs in the power supply voltage AVCC (AVCC drops downwards), the voltage at the control terminal of the second transistor M2 decreases accordingly. There is a certain time lag between the decrease in the power supply voltage AVCC and the voltage at the first terminal of the first switch MK1. When the voltage difference between the two reaches a certain magnitude, the second transistor M2 turns on. This is equivalent to short-circuiting the control terminal and the first terminal of the first switch MK1, turning off the first switch MK1 and preventing the interference from the power supply voltage AVCC from affecting the BG module. Furthermore, connecting the second terminal of the first switch MK1 to the power supply voltage AVCC and connecting the first terminal of the first switch MK1 to the BG module makes the positive terminal of the body diode of the first switch MK1 connected to the power supply voltage AVCC, and the negative terminal of the body diode connected to the BG module. Therefore, when the power supply voltage AVCC drops downwards, the body diode of the first switch MK1 will not conduct, thus not affecting the input voltage of the BG module.

[0068] In one embodiment, the discharge time of the first capacitor C1 can be adjusted by adjusting the values ​​of the first resistor R1 and the first capacitor C1. This can increase the discharge speed of the first capacitor C1, causing the voltage at the control terminal of the first transistor M1 to drop rapidly to zero as the power supply voltage AVCC jumps downward, thereby further strengthening the turn-off of the first switching transistor MK1.

[0069] like Figure 1As shown, there is a large third resistor R3 between the second terminal of the sixth transistor M6 and the power supply voltage AVCC, which is a weak drive node. When the BG module is established, the voltage signal at the control terminal of the seventh transistor M7 is low, and the seventh transistor M7 is in the turn-on state. At the same time, the second characterization signal BG_OK is in the high level state. The second switch MK2 is controlled by the high level second characterization signal BG_OK and is also in the turn-on state. The seventh transistor M7 and the second switch MK2 form an auxiliary pull-up path to help the voltage of the weak drive node (output terminal of the filter unit) build up to the power supply voltage AVCC more quickly.

[0070] Both the fifth transistor M5 and the seventh transistor M7 are in the on state when stable. When the power supply voltage AVCC drops, causing the second characteristic signal BG_OK to go low, the second switch MK2 turns off, thus preventing the body diode of the seventh transistor M7 from conducting and discharging the charge on the upper plate of the second capacitor C2 (the third resistor R3 discharges the charge on the second capacitor C2 more slowly and can be ignored in the short term). When the power supply voltage AVCC is re-established, since the second capacitor C2 still stores some charge, the node voltage settling time is reduced, and the voltage of the filter node also follows the re-established power supply voltage AVCC well.

[0071] refer to Figure 2 As shown, if the seventh transistor M7 and the second switch MK2 are not set, when positive noise interference occurs in the power supply voltage AVCC, the voltage signal BG_OK_PRE at the first end of the first capacitor C1 cannot quickly follow the power supply voltage AVCC to pull up because the first end of the second capacitor C2 is a weak drive node.

[0072] For example Figure 3 As shown, by setting the seventh transistor M7 and the second switch MK2, when the power supply voltage AVCC is subjected to positive noise interference, the voltage signal BG_OK_PRE at the first end of the second capacitor C2 can quickly follow the power supply voltage AVCC and be pulled up.

[0073] refer to Figure 4 As shown, if the first protection unit is not set, when the power supply voltage AVCC is subjected to negative noise interference, when the power supply voltage AVCC is used to directly power the BG module, the output voltage VBG of the BG module and the second characterization signal BG_OK will drop to a very low level completely following the power supply voltage AVCC. When the power supply voltage AVCC is re-established, the establishment speed of the second characterization signal BG_OK is also very slow.

[0074] For example Figure 5As shown, by setting the first protection unit, when the power supply voltage AVCC experiences negative noise interference, the voltage VCC supplied to the BG module at the first terminal of the first switching transistor MK1 stabilizes after a certain voltage drop, still meeting the minimum operating voltage of the analog circuit. The voltage VBG output by the BG module fluctuates less, maintaining a relatively stable bias voltage. By setting the second protection unit, when the power supply voltage AVCC is powered on again, the second characteristic signal BG_OK quickly establishes itself to the normal state.

[0075] The present invention also discloses a bandgap reference circuit, including the above-described protection circuit, input stage unit and output stage unit.

[0076] The protection circuit includes a first protection unit and a second protection unit; the input stage unit includes a BG module and a signal generation circuit 20; the output stage unit of the bandgap reference circuit includes a weak drive module, an auxiliary module and an output module.

[0077] The first protection unit is connected between the BG module and the power supply voltage AVCC to cut off the path between the BG module and the power supply voltage AVCC when the power supply voltage AVCC changes, so as to prevent the BG module from being affected by the power supply voltage AVCC change.

[0078] The BG module generates a voltage VBG. A signal generation circuit 20 is connected to the BG module to generate a first characteristic signal BG_PRE based on the voltage VBG, indicating whether the BG module has been established. A weak drive module inverts the first characteristic signal BG_PRE to generate a voltage signal BG_OK_PRE. An auxiliary module is connected to the output of the weak drive module to enhance the pull-up capability of the output of the weak drive module and accelerate the rise speed of the voltage signal BG_OK_PRE when it transitions to a high level. The output module shapes the voltage signal BG_OK_PRE to generate a second characteristic signal BG_OK.

[0079] The second protection unit is connected to the branch where the auxiliary module is located. When the second characterization signal BG_OK jumps downward under the influence of the power supply voltage AVCC, the second protection unit cuts off the branch where the auxiliary module is located based on the control of the second characterization signal BG_OK, slows down the discharge of charge on the weak drive module, and thus uses the charge stored in the weak drive module to speed up the establishment of the second characterization signal BG_OK when the power supply voltage AVCC is established.

[0080] The protection circuit proposed in this application is also applicable to other functional modules that generate level signals based on the AVCC power supply voltage.

[0081] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0082] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A protection circuit, characterized by, The application relates to a protection circuit for a circuit to be protected, the circuit to be protected comprising an input stage unit and an output stage unit, the protection circuit comprising a first protection unit and a second protection unit, the first protection unit being connected between the input stage unit and a power supply voltage to cut off a path between the input stage unit and the power supply voltage when the power supply voltage jumps; the output stage unit comprising a weak drive module, an auxiliary module and an output module, an input end of the weak drive module being connected to an output end of the input stage unit, an output end of the weak drive module being connected to an input end of the output module, the weak drive module outputting a drive signal based on a first characteristic signal output by the input stage unit, the output module being powered by the power supply voltage and generating a second characteristic signal based on control of the drive signal; the second protection unit and the auxiliary module being connected in series between the output end of the weak drive module and the power supply voltage, the auxiliary module being connected to the input end of the weak drive module and the output end of the input stage unit at the same time, the auxiliary module being used to improve a driving capability of the drive signal based on control of the first characteristic signal, the second protection unit being connected to the output end of the output module to control a branch between the output end of the weak drive module and the auxiliary module based on the second characteristic signal.

2. The protection circuit of claim 1, wherein, the first protection unit comprising a first response control module, a switch unit and a second response control unit, the first response control module being connected to the power supply voltage to be turned on based on control of the power supply voltage, the first response control module being connected to a control end of the switch unit to control the switch unit to be turned on based on turning on of the first response control module, a second end of the switch unit being connected to the power supply voltage, a first end of the switch unit being connected to the input stage unit, the second response control unit being connected to the power supply voltage, the control end of the switch unit and the first end of the switch unit, the second response control unit controlling a voltage between the control end of the switch unit and the first end of the switch unit based on the power supply voltage.

3. The protection circuit of claim 2, wherein, the switch unit comprising a first transistor, a control end of the first transistor being connected to the first response control module, a second end of the first transistor being connected to the power supply voltage, a first end of the first transistor being connected to the input stage unit.

4. The protection circuit of claim 2, wherein, the first response control module comprising a response unit and a first transistor, the response unit being connected to the power supply voltage to generate a control voltage varying with the power supply voltage based on the power supply voltage, a control end of the first transistor being connected to the response unit to receive the control voltage, a first end of the first transistor being connected to a reference voltage, a second end of the first transistor being connected to the control end of the switch unit to turn on the switch unit when the first transistor is turned on.

5. The protection circuit of claim 4, wherein, the response unit comprising a first resistor and a first capacitor, a first end of the first resistor being connected to the power supply voltage, a second end of the first resistor being connected to a first end of the first capacitor and the control end of the first transistor, a second end of the first capacitor being connected to the reference voltage.

6. The protection circuit of claim 2, wherein, the second response control unit comprising a second transistor, a second end of the second transistor being connected to the control end of the switch unit, a first end of the second transistor being connected to the first end of the switch unit, a control end of the second transistor being connected to the power supply voltage.

7. The protection circuit of claim 2, wherein, The first protection unit further comprises an interlocking unit connected with the power supply voltage, the first response control module and the control end of the switch unit, the first response control module being configured to control the interlocking unit to be turned on based on the power supply voltage, and the interlocking unit being configured to maintain the first response control module to be turned on based on the turning on of the interlocking unit.

8. The protection circuit of claim 7, wherein, The interlocking unit comprises a third transistor, a first end of the third transistor being connected with the power supply voltage, a control end of the third transistor being connected with the control end of the switch unit and the first response control module, and a second end of the third transistor being connected with the first response control module, the third transistor being configured to pull up the control voltage inside the first response control module to maintain the first response control module to be turned on when the third transistor is turned on.

9. The protection circuit of claim 1, wherein, The second protection unit comprises a second switch tube, a control end of the second switch tube being connected with the output end of the output module, a first end of the second switch tube being connected with the output end of the weak drive module, and a second end of the second switch tube being connected with the auxiliary module.

10. A bandgap reference circuit, characterized by The bandgap reference circuit comprises the protection circuit according to any one of claims 1 to 9, and further comprises an input stage unit and an output stage unit, the input stage unit comprising a BG module and a signal generation circuit, the first protection unit being connected between the BG module and the power supply voltage to cut off the path between the BG module and the power supply voltage when the power supply voltage jumps, and the signal generation circuit being connected with the BG module to generate a first representation signal representing whether the BG module is established. The output stage unit comprises a weak drive module, an auxiliary module and an output module, the weak drive module comprising a first inverter and a filter unit, an input end of the first inverter being connected with an output end of the input stage unit, and the filter unit being arranged at an output end of the first inverter to filter the signal output by the first inverter to generate a drive signal. The second protection unit and the auxiliary module are connected in series between the output end of the filter unit and the power supply voltage, the auxiliary module being further connected with an input end of the first inverter, the auxiliary module being configured to improve the driving capability of the drive signal based on the control of the first representation signal, the output module being powered by the power supply voltage and generating a second representation signal based on the control of the drive signal, and the second protection unit being further connected with an output end of the output module to control the on-off of the branch between the output end of the filter unit and the auxiliary module based on the second representation signal.

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