CN216215876U

CN216215876U - Electrostatic surge protection circuit of signal port and electronic equipment

Info

Publication number: CN216215876U
Application number: CN202122473422.9U
Authority: CN
Inventors: 蔡锦波; 黄正春
Original assignee: Shenzhen Penang Electronics Co ltd
Current assignee: Shenzhen Penang Electronics Co ltd
Priority date: 2021-10-13
Filing date: 2021-10-13
Publication date: 2022-04-05
Anticipated expiration: 2031-10-13

Abstract

The utility model discloses an electrostatic surge protection circuit of a signal port and electronic equipment. The electrostatic surge protection circuit of the signal port comprises: the device comprises a protection module and a level conversion module. The input end of the protection module is used as the input end of the electrostatic surge protection circuit of the signal port, and the grounding end is connected with a ground signal; the protection module is used for conducting a transmission path between the input end and the grounding end of the protection module when static electricity and/or surge occur; the control end of the level conversion module is electrically connected with the output end of the protection module, the first input end is connected with a power signal, the second input end is connected with a ground signal, and the output end is electrically connected with a signal port of the integrated circuit chip; the level conversion module is used for converting a power supply signal into a first control signal to be output or converting a ground signal into a second control signal to be output under the control of an output signal of the protection module. The embodiment of the utility model can improve the electrostatic surge protection effect on the signal port and improve the communication reliability of the integrated circuit chip.

Description

Electrostatic surge protection circuit of signal port and electronic equipment

Technical Field

The embodiment of the utility model relates to the technical field of protection circuits, in particular to an electrostatic surge protection circuit of a signal port and electronic equipment.

Background

The wired communication between the electronic device and the external device is established through a signal port of an Integrated Circuit (IC) chip (IC) built in the electronic device, for example, through an IO port (input/output port). If the signal port is exposed outside the electronic device, the signal port is easily subjected to ESD (Electro-Static Discharge) and surge impact from a charged body such as a human body, and the integrated circuit chip may be damaged. Therefore, electrostatic surge protection is required for signal ports of integrated circuit chips.

In the prior art, an electrostatic surge protection circuit is usually connected in parallel with an integrated circuit chip as a leakage module of peak voltage caused by surge or static electricity; however, the interference signal caused by surge or static electricity is usually a transient effect, and if the protection circuit cannot respond in time, the transient spike is still applied to the signal port of the integrated circuit chip, which affects the protection effect. Even if the guard circuit includes a portion connected in series between the signal transmitting terminal and the signal port of the integrated circuit chip, since the signal transmitted to the signal port must satisfy the voltage threshold value of the signal port to be correctly recognized, the impedance of the series portion cannot be set too high in order to reduce the attenuation of the input signal in the guard circuit. Generally speaking, then, there is a low impedance path between the signal output port and the signal port of the integrated circuit chip, and the spike voltage still causes impact to the integrated circuit chip before the protection circuit acts in response to static electricity or surge. Therefore, the electrostatic surge protection circuit of the signal port of the integrated circuit chip in the prior art has the problem of low protection reliability.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides an electrostatic surge protection circuit of a signal port and electronic equipment, which are used for improving the electrostatic surge protection effect of the signal port and improving the communication reliability of an integrated circuit chip.

In a first aspect, an embodiment of the present invention provides an electrostatic surge protection circuit for a signal port. The electrostatic surge protection circuit of the signal port comprises:

the protection module comprises an input end, a grounding end and an output end; the input end of the protection module is used as the input end of the electrostatic surge protection circuit of the signal port, and the grounding end of the protection module is connected with a ground signal; the protection module is used for conducting a transmission path between an input end and a ground end of the protection module when static electricity and/or surge occur;

the level conversion module comprises a control end, a first input end, a second input end and an output end; the control end of the level conversion module is electrically connected with the output end of the protection module, the first input end of the level conversion module is connected with a power supply signal, the second input end of the level conversion module is connected with a ground signal, and the output end of the level conversion module is electrically connected with a signal port of the integrated circuit chip; the level conversion module is used for converting the power supply signal into a first control signal to be output or converting the ground signal into a second control signal to be output under the control of the output signal of the protection module.

Optionally, the protection module comprises:

the protection unit comprises an input end, an output end and a grounding end; the first end of the protection unit is used as the input end of the protection module, and the grounding end of the protection unit is used as the grounding end of the protection module;

the high impedance unit comprises an input end, an output end and a grounding end; the input end of the high-impedance unit is electrically connected with the output end of the protection unit, the grounding end of the high-impedance unit is connected to the ground signal, and the output end of the high-impedance unit serves as the output end of the protection module.

Optionally, the guard unit comprises: a first protective element and a reactive element; the first end of the first protection element is electrically connected with the first end of the reactive element and serves as the input end of the protection unit; the second end of the first protection element is used as the grounding end of the protection unit; the second end of the reactive element serves as an output end of the protection unit.

Optionally, the protection unit further comprises: a second protection element; the first end of the second protection element is electrically connected with the second end of the reactive element, and the second end of the second protection element is connected to the ground signal.

Optionally, the high impedance unit includes: a first resistor and a second resistor; a first end of the first resistor is used as an input end of the high impedance unit; the second end of the first resistor is electrically connected with the first end of the second resistor and serves as the output end of the high-impedance unit; and the second end of the second resistor is used as the grounding end of the high-impedance unit.

Optionally, the resistance value of the first resistor is greater than or equal to 20k Ω.

Optionally, the level conversion module includes:

the first conversion unit comprises a control end, a first input end, a second input end and an output end; the control end of the first conversion unit is used as the control end of the level conversion module, the first input end of the first conversion unit is connected with the power signal, and the second input end of the first conversion unit is connected with the ground signal;

the second conversion unit comprises a control end, a first input end, a second control end and an output end; the control end of the second conversion unit is electrically connected with the output end of the first conversion unit, the first input end of the second conversion unit is connected with the power signal, the second input end of the second conversion unit is connected with the ground signal, and the output end of the second conversion unit is used as the output end of the level conversion module.

Optionally, the first conversion unit comprises: a first transistor and a third resistor; a control electrode of the first transistor is used as a control end of the first conversion unit, and a first electrode of the first transistor is used as a second input end of the first conversion unit; a second pole of the first transistor is electrically connected with a second end of the third resistor and is used as an output end of the first conversion unit; a first end of the third resistor is used as a first input end of the first conversion unit;

the second conversion unit includes: a second transistor, a fourth resistor, and a fifth resistor; a first end of the fourth resistor is used as a control end of the second conversion unit, and a second end of the fourth resistor is electrically connected with a control electrode of the second transistor; a first pole of the second transistor is used as a second input end of the second conversion unit; a second pole of the second transistor is electrically connected with a second end of the fifth resistor and is used as an output end of the second conversion unit; and a first end of the fifth resistor is used as a first input end of the second conversion unit.

In a second aspect, an embodiment of the present invention further provides an electronic device. The electronic device includes: an integrated circuit chip and a signal port electrostatic surge protection circuit as provided in any of the embodiments of the present invention.

Optionally, the electronic device further comprises: a main board; the main board includes: an input interface; the integrated circuit chip and the electrostatic surge protection circuit of the signal port are integrated on the mainboard; and the input end of the electrostatic surge protection circuit of the signal port is electrically connected with the input interface.

The electrostatic surge protection circuit of the signal port provided by the embodiment of the utility model is provided with a protection module and a level conversion module. The protection module can provide a leakage path for an interference signal generated when static electricity or surge occurs in the input signal, so that an effective signal in the input signal is transmitted to a post-stage circuit. The level conversion module can convert the signal transmitted to the control end of the level conversion module into a first control signal or a second control signal for output, namely, the attenuation of the effective signal in the transmission process is effectively compensated and restored, more attenuation allowance is provided for the effective signal, and a transmission path between the input end and the output end of the protection module can be set to be higher impedance. Therefore, even if the conduction between the input end of the protection module and the ground end has time delay, the interference signal can be attenuated more before reaching the control end of the level conversion module, and the electrostatic surge protection capability is further improved. And, there is not the transmission path of direct intercommunication between the control end of level transition module and the output, therefore, level transition module can play the effect of blockking to interference signal, makes interference signal can't transmit to the signal port, provides further protection. Therefore, the embodiment of the utility model can improve the electrostatic surge protection effect on the signal port and improve the communication reliability of the integrated circuit chip.

Drawings

Fig. 1 is a schematic structural diagram of an electrostatic surge protection circuit of a signal port in the prior art;

fig. 2 is a schematic diagram of a connection relationship between an electrostatic surge protection circuit of a signal port and an integrated circuit chip according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an electrostatic surge protection circuit of a signal port according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a connection relationship between an electronic device and an external device according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the utility model and are not limiting of the utility model. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

As described in the background art, the electrostatic surge protection circuit of the signal port of the integrated circuit chip in the prior art has the problem of low protection reliability. The inventor researches the following reasons:

the electrostatic surge protection circuit of the signal port of the integrated circuit chip is mainly formed by stacking components such as transistors. The higher the required protection grade is, the more components are required by the protection circuit, and the larger the volume and the cost of the protection circuit are; the excessive volume is not beneficial to flexible placement and routing of component positions in the design of a downstream company PCBA (Printed Circuit Board Assembly), so that the protection structure provided by the signal port (e.g., IO port) of most integrated Circuit chips cannot meet the standard requirements of surge and ESD of the finished product of electronic equipment, and an additional protection Circuit needs to be added to the PCBA designed by the downstream company.

Fig. 1 is a schematic structural diagram of an electrostatic surge protection circuit of a conventional signal port. Referring to fig. 1, an electrostatic surge protection circuit 100 of a signal port in the prior art exemplarily includes a protection module 101, a resistor R01, a resistor R02, and a capacitor C01. Wherein, the protection module 101 and the integrated circuit chip U01 are in parallel connection; the resistor R01, the capacitor C01 and the resistor R02 are connected in series between the interface J01 and the signal port 01 of the integrated circuit chip U01. The electrostatic surge protection circuit has the following defects:

1) the protection module 101 is connected in parallel with the protected integrated circuit chip U01, and when a surge or ESD event occurs, the protection module 101 needs a response time, and a spike voltage before the response is applied to the protection module 101 and the signal port 01 at the same time, the spike voltage still causes an impact on the signal port 01.

2) The integrated circuit chip U01 needs to establish a correct communication logic 0 or 1 by recognizing the high and low levels of the signal from the transmitter, and the signal transmitted to the signal port 01 must satisfy the voltage threshold value to be correctly recognized. In the prior art, the resistor R01 and the resistor R02 are connected in series in the communication loop, which inevitably limits the resistance value not to be too large, inevitably divides the voltage too large to cause signal loss, and cannot satisfy the threshold voltage value of the signal port 01, thereby affecting communication.

In summary, a low impedance path is still provided from the interface J01 to the signal port 01, and before the protection module 101 responds, the signal port 01 of the integrated circuit chip U01 will break down and burn out when it cannot withstand a surge or ESD spike. Secondly, surge and ESD events can also generate oscillation and Electromagnetic Interference (EMI), and the low impedance path in the prior art provides a friendly conduction path for the Interference source, so that the Interference source can easily enter the signal port 01, and then the Interference source is coupled into an internal system of the integrated circuit chip U01, which may cause a timing disorder of some units of the system to cause the signal port 01 to fail to communicate, and the recovery can be performed after power-off and restart.

The circuit configuration of single-ended communication is exemplarily shown in fig. 1, but the above-described problem does not exist only in the single-ended communication configuration. For a differential communication circuit, a buffer path formed by a capacitor and a resistor and a protection module are added between an interface and an integrated circuit chip. However, in order to ensure the communication correctness, a low impedance path is still formed between the interface and the communication port, before the protection module acts, the peak voltage caused by static electricity or surge still impacts the communication port, and an interference source still easily enters the communication port.

Moreover, for the protection circuit for power protection in the prior art, the protection concept is similar to that in fig. 1, the interface J01 is replaced by a power supply port, and the integrated circuit chip U01 is replaced by a power consumption device, that is, the power protection circuit. Since the protection circuit is arranged in the power supply path of the power supply, in order to ensure the power supply efficiency and reduce the loss, the part of the protection circuit connected in series in the current transmission path also needs to be a low-impedance path, and the protection effect is difficult to ensure.

On the basis, no matter any one protection element of a thermistor, an electronic fuse and a transistor is adopted as the protection module 101, a certain response time is required, and the nanosecond-level surge and the nanosecond-level or microsecond-level high-energy signal of ESD are difficult to react in time.

Based on the above research, the embodiment of the utility model provides an electrostatic surge protection circuit for a signal port, which can be arranged between an input structure of a mainboard and the signal port of an integrated circuit chip to realize effective protection of static electricity and surge. Fig. 2 is a schematic diagram of a connection relationship between an electrostatic surge protection circuit of a signal port and an integrated circuit chip according to an embodiment of the present invention. Referring to fig. 2, the electrostatic surge protection circuit 10 of the signal port includes: a guard module 110 and a level shift module 120.

The protection module 110 includes an input terminal 11, a ground terminal 13, and an output terminal 12; an input end 11 of the protection module 110 is used as an input end of the electrostatic surge protection circuit 10 of the signal port, and a ground end 13 is connected to a ground signal GND; the protection module 110 is used to conduct a transmission path between its input terminal 11 and the ground terminal 13 when static electricity and/or surge occurs. The level shift module 120 includes a control terminal 23, a first input terminal 21, a second input terminal 22, and an output terminal 24; the control terminal 23 of the level shift module 120 is electrically connected to the output terminal 12 of the protection module 110, the first input terminal 21 is connected to the power signal VCC, the second input terminal 22 is connected to the ground signal GND, and the output terminal 24 is electrically connected to the signal port 31 of the integrated circuit chip U1; the level converting module 120 is configured to convert the power signal VCC into a first control signal output or convert the ground signal GND into a second control signal output under the control of the output signal of the guarding module 110.

Exemplarily, the power supply signal VCC may be a direct current voltage signal; the signal port 31 may be an IO port. The electrostatic surge protection circuit 10 and the integrated circuit chip U1 of the signal port can be integrated on a main board of the electronic device; the input signal VIN may be a communication signal output by an external device and transmitted to the integrated circuit chip U1 via an input interface on the motherboard.

Illustratively, the operation process of the electrostatic surge protection circuit 10 of the signal port includes:

when there is no static electricity or surge, the input signal VIN is a valid signal and does not include an interference signal. The transmission path between the input terminal 11 and the output terminal 12 of the protection module 110 is turned on, and the transmission path between the input terminal 11 and the ground terminal 13 of the protection module 110 is turned off; the input signal VIN is transmitted to the control terminal 23 of the level shift module 120 via the input terminal 11 and the output terminal 12 of the protection module 110. The output signal (denoted as the intermediate signal) of the guard module 110 controls the operation state of the level shift module 120. For example, when the intermediate signal is at a high level, the transmission path between the first input terminal 21 and the output terminal 24 of the level shift module 120 is controlled to be turned on, so as to convert the power signal VCC into a first control signal, and output the first control signal, which is, for example, at a higher high level; when the intermediate signal is at a low level, the transmission path between the second input terminal 22 and the output terminal 24 of the level shift module 120 is controlled to be turned on, and the ground signal GND is converted into a second control signal, which is, for example, at a lower low level, and is output. The above process is only exemplary and not limiting to the present invention, and the switching logic inside the level shifting module 120 can be set according to actual requirements.

When static electricity or surge occurs, phenomena such as short-time overvoltage, overcurrent or oscillation can be caused, and the phenomena are reflected in an input signal VIN as follows: the input signal VIN includes two portions, i.e., a valid signal and an interference signal. At this time, the transmission path between the input terminal 11 of the protection module 110 and the ground terminal 13 is turned on, and a leakage path of the interference signal is provided, so that the interference signal is leaked to the ground through the input terminal 11 of the protection module 110 and the ground terminal 13, and is not transmitted to the subsequent circuit; meanwhile, the transmission path between the input terminal 11 and the output terminal 12 of the protection module 110 is kept on, so that the valid signal is normally transmitted backward. Through the protection effect of the protection module 110, the working process of the level conversion module 120 is not affected by static electricity or surge, and the normal working state is maintained.

The level recognition range of the control terminal 23 of the level shift module 120 may be greater than the level recognition range of the signal port 31; the first control signal and the second control signal may be set within a range of level discrimination capability of the signal port. In this way, the level shift module 120 outputs the first control signal or the second control signal according to the signal transmitted to the control terminal 23 thereof, which is equivalent to compensate and restore the attenuation of the valid signal in the input signal VIN during the transmission process, so that the first control signal and the second control signal can indicate the level represented by the valid signal to be correctly and effectively identified by the signal port 31. That is, the level shift module 120 is configured to provide more attenuation margins for the effective signals in the input signal VIN, so that compared with the prior art, on the basis of ensuring the accuracy of signal identification, the transmission path between the input end 11 and the output end 12 of the protection module 110 can be configured to have higher impedance; even if there is a delay in the conduction between the input terminal 11 of the protection module 110 and the ground terminal 13, the interference signal is attenuated more in the transmission path between the input terminal 11 and the output terminal 12 of the protection module 110, and will not impact the signal port 31, and will not affect the signal identification of the signal port 31.

Specifically, the lower limit of the high level identification of the control terminal 23 of the level shift module 120 may be lower than the lower limit of the high level identification of the signal port 31, and the upper limit of the low level identification of the control terminal 23 of the level shift module 120 may be higher than the upper limit of the low level identification of the signal port 31; and the first control signal may be higher than the lower limit of the high level recognition of the signal port 31 and the second control signal may be lower than the upper limit of the low level recognition of the signal port 31. For example, the control terminal 23 of the level shift module 120 may recognize a level greater than 1V as a high level and recognize a level lower than 0.7V as a low level; the signal port 31 may recognize a level greater than 1.5V as a high level and a level lower than 0.3V as a low level. The first control signal is 2V and the second control signal is 0.1V. Assuming that the effective signal is 1.8V, the effective signal is attenuated to 1.2V by the protection module 110, and cannot be effectively identified if the effective signal is directly transmitted to the signal port 31; however, the control terminal 23 of the level shift module 120 can recognize 1.2V as a high level, so as to control the conduction of the transmission path between the first input terminal 21 and the output terminal 24, and control the output of the first control signal of 2V; the signal port 31 can recognize the first control signal of 2V as high level, thereby completing the correct recognition of the signal. Therefore, the level shift module 120 can effectively compensate, restore and even amplify the attenuated effective signal.

The electrostatic surge protection circuit 10 of the signal port according to the embodiment of the present invention is provided with a protection module 110 and a level conversion module 120. The protection module 110 may provide a leakage path for an interference signal generated when static electricity or surge occurs in the input signal VIN, so that a valid signal in the input signal VIN is transmitted to a subsequent circuit. The level shift module 120 may convert the signal transmitted to the control terminal 23 thereof into the first control signal or the second control signal for outputting, that is, effectively compensate and restore the attenuation of the effective signal during the transmission process, so as to provide more attenuation margin for the effective signal, so that the transmission path between the input terminal 11 and the output terminal 12 of the protection module 110 may be set to have higher impedance. Even if there is a delay in the conduction between the input terminal 11 of the protection module 110 and the ground terminal 13, the interference signal is attenuated more before reaching the control terminal of the level shift module 120, thereby further improving the protection against electrostatic surge. Moreover, there is no transmission path directly connected between the control terminal 23 and the output terminal 24 of the level shift module 120, so that the level shift module 120 can block the interference signal, so that the interference signal cannot be transmitted to the signal port 31, thereby providing further protection. Therefore, the embodiment of the utility model can improve the electrostatic surge protection effect on the signal port 31 and improve the communication reliability of the integrated circuit chip U1.

Fig. 3 is a schematic structural diagram of an electrostatic surge protection circuit of a signal port according to an embodiment of the present invention. Referring to fig. 3, in one embodiment, optionally, the protection module comprises: a guard unit 111 and a high impedance unit 112. A first end of the protection unit 111 is used as an input end of the protection module 110, and is accessed with an input signal VIN; the ground terminal of the protection unit 111 is used as the ground terminal of the protection module and is connected to the ground signal GND. The input end of the high impedance unit 112 is electrically connected to the output end of the protection unit 111, the ground end of the high impedance unit 112 is connected to the ground signal GND, and the output end of the high impedance unit 112 serves as the output end of the protection module 110.

The protection unit 111 is used for providing a leakage path of an interference signal when static electricity or surge occurs; the high impedance unit 112 provides a high impedance transmission path from the protection unit 110 to the level shift module 120, and can attenuate the interference signal as much as possible before the protection unit 111 responds on the basis of ensuring the identification capability of the level shift module 120.

With continued reference to fig. 3, on the basis of the foregoing embodiments, optionally, the level conversion module 120 includes: a first conversion unit 121 and a second conversion unit 122. The control end of the first converting unit 121 serves as the control end of the level converting module 120, and is electrically connected to the output end of the protection module 110; a first input terminal of the first converting unit 121 is connected to the power signal VCC, and a second input terminal of the first converting unit 121 is connected to the ground signal GND. The control terminal of the second converting unit 122 is electrically connected to the output terminal of the first converting unit 121, the first input terminal of the second converting unit 122 is connected to the power signal VCC, the second input terminal of the second converting unit 122 is connected to the ground signal GND, and the output terminal of the second converting unit 122 is used as the output terminal of the level shifting module 120.

In this embodiment, the first converting unit 121 is configured to convert the output signal of the protection module 110 into an intermediate control signal, and the second converting unit 122 is configured to convert the intermediate control signal into the output signal VOUT. The output signal VOUT is a first control signal or a second control signal according to the level of the intermediate control signal. For example, according to actual requirements such as signal transmission and wiring, the first input terminal of the first converting unit 121 and the first input terminal of the second converting unit 122 may also be connected to different power source terminals to receive different power source signals.

The above embodiments exemplarily show the functional unit structure of the electrostatic surge protection circuit 10 of the signal port, and the following description is provided for a specific structure that the electrostatic surge protection circuit 10 of the signal port may have, but is not intended to limit the present invention.

With continued reference to fig. 3, on the basis of the above embodiments, optionally, the protection unit 111 includes: a first protective element T1 and a reactive element B1; a first end of the first protection element T1 is electrically connected with a first end of the reactive element B1 and serves as an input end of the protection unit 111; the second end of the first protection element T1 serves as the ground terminal of the protection unit 111; the second end of the reactive element B1 serves as the output end of the guard unit 111.

Illustratively, the first protection element T1 may be a Voltage dependent resistor, a zener diode, or a Transient Voltage Super (TVS) for clamping a Voltage; the reactive element B1 may be an inductor for suppressing current jumps. Wherein, the reactive element B1 can be selected according to different protection levels; the reactive element B1 may not be provided when the protection level is low; when the protection level is high, the magnetic beads can be arranged, so that ESD shock can be better inhibited.

With continued reference to fig. 3, on the basis of the foregoing embodiments, optionally, the protection unit 111 further includes: a second protection element T2; the first terminal of the second protection element T2 is electrically connected to the second terminal of the reactive element B1, and the second terminal of the second protection element T2 is connected to the ground signal GND.

The second protection element T2 is used to discharge the residual energy transmitted after passing through the first protection element T1, and forms a double protection with the first protection element T1. By such an arrangement, the protection level of the protection circuit can be increased, or the requirement for the voltage endurance capability of the control terminal of the level shift module 120 can be reduced. The second protection element T2 may be a voltage dependent resistor, a zener diode, or a transient diode, for example.

With continued reference to fig. 3, in one embodiment, the high impedance unit 112 optionally includes: a first resistor R1 and a second resistor R2; a first terminal of the first resistor R1 serves as an input terminal of the high impedance unit 112; the second end of the first resistor R1 is electrically connected with the first end of the second resistor R2 and serves as the output end of the high impedance unit 112; the second terminal of the second resistor R2 serves as the ground terminal of the high impedance unit 112.

Wherein, the resistance value of the first resistor R1 is greater than or equal to 20k omega. The resistance of the second resistor R2 may be selected according to practical requirements, for example, the resistance of the second resistor R2 is greater than or equal to 20k Ω, or the second resistor R2 may not be provided.

With continued reference to fig. 3, on the basis of the above embodiments, optionally, the first conversion unit 121 includes: a first transistor Q1 and a third resistor R3; a control electrode of the first transistor Q1 serves as a control terminal of the first conversion unit 121; a first pole of the first transistor Q1 is used as a second input terminal of the first conversion unit 121, and is connected to the ground signal GND; a second pole of the first transistor Q1 is electrically connected to a second end of the third resistor R3 and serves as an output terminal of the first switching unit 121; a first end of the third resistor R1 is used as a first input end of the first converting unit 121, and is connected to the power signal VCC.

Alternatively, the first resistor R1 and the second resistor R2 in the high impedance unit 112 may be multiplexed as a voltage dividing circuit of the control electrode of the first transistor Q1. The resistance values of the first resistor R1 and the second resistor R2 can be adjusted according to the level of the input signal VIN and the withstand voltage value of the control electrode of the first transistor Q1, so that the voltage transmitted to the control electrode of the first transistor Q1 can be controlled, and the switching state of the first transistor Q1 can be controlled.

With continued reference to fig. 3, on the basis of the above embodiments, optionally, the second conversion unit 122 includes: a second transistor Q2, a fourth resistor R4, and a fifth resistor R5; a first terminal of the fourth resistor R4 serves as a control terminal of the second switching unit 122, and a second terminal of the fourth resistor R4 is electrically connected to a control electrode of the second transistor Q2; a first pole of the second transistor Q2 is used as a second input terminal of the second conversion unit 122, and is connected to the ground signal GND; a second pole of the second transistor Q2 is electrically connected to a second terminal of the fifth resistor R5 and serves as an output terminal of the second switching unit 122; a first end of the fifth resistor R5 is used as a first input end of the second conversion unit, and is connected to the power supply signal VCC. If a pull-up resistor is provided inside the integrated circuit chip, the fifth resistor R5 may not be provided.

The working principle of the protection circuit is described below with reference to the specific structure of fig. 3:

illustratively, the resistances of the first resistor R1 and the second resistor R2 can reach 20k Ω and above, the resistances of the third resistor R3 and the fifth resistor R5 can reach 50k Ω and above, and the resistance of the fourth resistor R4 can reach 10k Ω and above. The first transistor Q1 and the second transistor Q2 may be NMOS transistors or NPN transistors; then, the control electrode of the transistor may be a base electrode of the NPN transistor or a gate electrode of the NMOS transistor, the first electrode of the transistor may be a source electrode of the NMOS transistor or an emitter electrode of the NPN transistor, and the first electrode of the transistor may be a drain electrode of the NMOS transistor or a collector electrode of the NPN transistor. The second pole of the first transistor Q1 is defined as node N1, and the second pole of the second transistor Q2 is defined as node N2.

For the level translation module 120: when the input signal VIN is at a high level, the first transistor Q1 is turned on in response to the high level, a low-resistance state of several ohms is present between the node N1 and the second input terminal of the first switching unit 121, the power signal VCC is mainly applied to the third resistor R3, the node N1 is at a low level, the control electrode of the second transistor Q2 is pulled low, the second transistor Q2 is turned off, the node N2 is at a high-resistance state of megohms at the second input terminal of the second switching unit 122, and the node N2 outputs a high level. When the input signal VIN is at a low level, the first transistor Q1 is turned off in response to the low level, a high-impedance mega-ohm level is present between the node N1 and the second input terminal of the first switching unit 121, the power signal VCC is mainly applied to the first transistor Q1, and the control electrode of the second transistor Q2 is pulled high; the second transistor Q2 turns on, assumes a low impedance state of several ohms, and the node N2 outputs a low level. The level conversion module 120 performs the level conversion through the above process.

For the guard module 110: when a surge or ESD event occurs at the input port of the input signal VIN, the first protection element T1 discharges a main current to the ground, the second protection element T2 discharges a residual current to the ground, and the energy remaining after the surge or ESD is discharged through the first protection element T1 and the second protection element T2 is weak. The first protection element T1, the second protection element T2 and the high impedance unit 112 are in a parallel relationship as seen from the input port to ground; when the applied voltages (denoted as U) of the three branches are equal, the current on the communication path (i.e., the current of the branch in which the first resistor R1 is located, denoted as I) is calculated by the following formula: and I is U/Rt1+ U/Rt2+ U/(R1+ R2). Where Rt1 is an equivalent resistance value of the first protection element T1, and Rt1 is an equivalent resistance value of the second protection element T2. When a surge or an ESD event occurs, the Rt1 and the Rt2 present a low impedance milliohm level, the resistance value of the first resistor R1 is 20k Ω or more, and it can be known that the first resistor R1 blocks and forces the current I to be discharged to the ground through the first protection element T1 and the second protection element T2; the surge or ESD voltage can be regarded as being short-circuited to the ground by the first protection element T1 and the second protection element T2, so that the voltage current of the surge or ESD hardly enters the control electrode of the first transistor Q1, so that the control electrode of the first transistor Q1 is well protected from being burned by the surge or ESD breakdown.

Moreover, the input signal VIN is transmitted through the high impedance path, and no matter how fast the surge and ESD are generated or whether the response of the two protection elements is delayed, the high impedance path will block the transmission of the interference signal, and the signal port 31 will not be impacted because the response of the protection unit 111 is slow. Specifically, assuming that interference signals such as oscillation generated by surge or ESD, EMI interference sources, etc. are transmitted backward before the protection unit 111 acts, the transmission path is: to the signal port 31 via the reactive element B1, the first resistor R1, the first transistor Q1, the third resistor R3, and the fifth resistor R5; or to the signal port 31 via the reactive element B1, the first resistor R1, the first transistor Q1, the fourth resistor R4, and the second transistor Q2. Then, the series impedance of the transmission path of the interference signal to the signal port 31 reaches at least 30k Ω, and the interference signal is mainly consumed and blocked by the series resistor, so that the signal port 31 of the integrated circuit chip U1 is well prevented from being interfered, and is further coupled to the system, so that the system can stably work and normal communication is ensured.

In summary, the electrostatic surge protection circuit 10 of the signal port has the following advantages:

1) the attenuation of the effective signal in the input signal VIN is well compensated. Examples are as follows: the attenuation of the signal transmitted to the control electrode of the first transistor Q1 is too low (e.g., from 1.8V to 1V), and if the signal port is directly transmitted, the signal port may not be able to identify whether it is high or low; however, in this embodiment, the first transistor Q1 and the second transistor Q2 are selected as devices with lower turn-on voltages (for example, NMOS transistor is selected, the gate voltage is 1V turned on, and the base voltage of NPN transistor is 0.7V turned on), so that the attenuated signal can be normally reacted, and the signal port is restored to the original level, thereby improving the reliability of communication.

2) The protection circuit has extremely high input impedance, can provide excellent ESD protection by matching with two protection elements, is equivalent to patch a signal port when an integrated circuit chip with a weak ESD resistance of the signal port is selected by mistake in the process of designing a product, does not need to evaluate other integrated circuit chips again to design the product, and greatly saves the product development time. Or, the protection circuit provides more selection ranges for users (such as electronic product design companies), so that the users can select the integrated circuit chip with weak signal port ESD resistance, the cost of the integrated circuit is saved, and the product has higher competitiveness; at the same time, the produced integrated circuit chips can be better sold without worry.

3) The protection circuit has extremely high input impedance, can well resist the interference generated by surge and ESD, can well inhibit the oscillation and EMI interference source generated by the surge and the ESD, avoids the signal port of the integrated circuit chip from being interfered and then coupled to a system, can ensure that the system stably works and ensures normal communication. The high-impedance matched protection element can provide extremely high protection level for a signal port of the integrated circuit chip and prevent the signal port from being burnt by surge and ESD events; providing the necessary condition for the stable operation of the signal port of the integrated circuit chip.

The embodiment of the utility model also provides electronic equipment which comprises an integrated circuit chip and the electrostatic surge protection circuit of the signal port, and the electronic equipment has corresponding beneficial effects. In the electrostatic surge protection circuit of the signal port, the output end of the level conversion module is electrically connected with the signal port of the integrated circuit chip, and the signal port can be an IO port.

Fig. 4 is a schematic diagram of a connection relationship between an electronic device and an external device according to an embodiment of the present invention. Referring to fig. 4, in an embodiment, optionally, the electronic device further includes: a main board 1; the motherboard 1 includes an input interface J1. The integrated circuit chip U1 and the electrostatic surge protection circuit 10 of the signal port are integrated on the mainboard 1; the input terminal of the electrostatic surge protection circuit 10 of the signal port is electrically connected to the input interface J1. An input signal transmitted from the outside is transmitted to the electrostatic surge protection circuit 10 of the signal port through the interface J1.

Illustratively, the external device U2 includes an output terminal 41 and a ground terminal 42, the output terminal 41 of the external device U2 is electrically connected to the interface J1 for providing an input signal to the interface J1; the ground terminal 42 of the external device U2 is connected to the ground signal GND.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the utility model. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An electrostatic surge protection circuit of a signal port, comprising:

2. The electrostatic surge protection circuit for a signal port of claim 1, wherein the protection module comprises:

3. The electrostatic surge protection circuit for a signal port according to claim 2, wherein the protection unit comprises: a first protective element and a reactive element; the first end of the first protection element is electrically connected with the first end of the reactive element and serves as the input end of the protection unit; the second end of the first protection element is used as the grounding end of the protection unit; the second end of the reactive element serves as an output end of the protection unit.

4. The electrostatic surge protection circuit for a signal port of claim 3, wherein the protection unit further comprises: a second protection element; the first end of the second protection element is electrically connected with the second end of the reactive element, and the second end of the second protection element is connected to the ground signal.

5. The electrostatic surge protection circuit for a signal port according to claim 2, wherein the high impedance unit comprises: a first resistor and a second resistor; a first end of the first resistor is used as an input end of the high impedance unit; the second end of the first resistor is electrically connected with the first end of the second resistor and serves as the output end of the high-impedance unit; and the second end of the second resistor is used as the grounding end of the high-impedance unit.

6. The circuit of claim 5, wherein the first resistor has a resistance greater than or equal to 20k Ω.

7. The electrostatic surge protection circuit for a signal port of claim 1, wherein the level conversion module comprises:

8. The electrostatic surge protection circuit for a signal port of claim 7,

the first conversion unit includes: a first transistor and a third resistor; a control electrode of the first transistor is used as a control end of the first conversion unit, and a first electrode of the first transistor is used as a second input end of the first conversion unit; a second pole of the first transistor is electrically connected with a second end of the third resistor and is used as an output end of the first conversion unit; a first end of the third resistor is used as a first input end of the first conversion unit;

9. An electronic device, comprising: an integrated circuit chip and a signal port electrostatic surge protection circuit as claimed in any one of claims 1 to 8.

10. The electronic device of claim 9, further comprising: a main board; the main board includes: an input interface; the integrated circuit chip and the electrostatic surge protection circuit of the signal port are integrated on the mainboard; and the input end of the electrostatic surge protection circuit of the signal port is electrically connected with the input interface.