Disclosure of Invention
In view of the above, an objective of the present invention is to provide an electrostatic protection circuit, which further reduces the design cost of the circuit and improves the design efficiency of the circuit.
According to the present invention, there is provided an electrostatic protection circuit comprising: the release unit is connected with the signal end and used for releasing energy to the signal end according to the trigger signal; a trigger unit for providing the trigger signal; the trigger unit comprises a first transistor, the first transistor is conducted under the action of parasitic capacitance coupling between a first end and a control end of the first transistor to provide starting current, the first end of the first transistor is connected with the signal end, and when the first transistor is conducted, the trigger unit provides the trigger signal according to the starting current.
Preferably, the trigger unit further includes a first resistor connected between the second terminal and the control terminal of the first transistor.
Preferably, the trigger unit further includes: the 1 st to N-stage trigger circuits, the 1 st stage trigger circuit generates the 1 st stage output current according to the starting current, the 2 nd to N-stage trigger circuits generate the 2 nd to N-stage output currents according to the 1 st to N-1 stage output currents respectively, and N is a non-zero natural number; and a conversion circuit generating the trigger signal according to the output current of the nth stage.
Preferably, at least one stage of the trigger circuit is used for amplifying the starting current or the output current of the trigger circuit of the previous stage.
Preferably, each stage of the flip-flop circuit includes: the input end receives the starting current or the corresponding output current; the output end provides the output current of the current stage; a control end of the second transistor is connected with the input end, a first end of the second transistor is connected with the signal end, and a second end of the second transistor is connected with the output end; and a second resistor connected between the input terminal and the output terminal.
Preferably, the conversion circuit includes a third resistor, a first terminal of the third resistor is connected to the output terminal of the nth stage trigger circuit to provide the trigger signal, and a second terminal of the third resistor receives a reference ground voltage.
Preferably, the bleeding unit includes a third transistor, a first terminal of the third transistor is connected to the signal terminal, a second terminal of the third transistor receives the reference ground voltage, and a control terminal of the third transistor receives the trigger signal.
Preferably, the electrostatic protection circuit further includes a diode, an anode of the diode is connected to the control terminal of the third transistor, and a cathode of the diode is connected to the first terminal of the third transistor.
Preferably, the first transistor is a triode and/or a field effect transistor.
Preferably, the second transistor is a triode and/or a field effect transistor.
Preferably, the signal terminal is used for receiving a high level voltage.
The electrostatic protection circuit provided by the invention has the beneficial effects that: the ESD circuit comprises a trigger unit, a signal end, a base electrode, a field effect transistor and a coupling capacitor, wherein the coupling capacitor between the collector electrode and the base electrode of the triode or between the drain electrode and the grid electrode of the field effect transistor is used for replacing a high-voltage capacitor to generate starting current, the trigger unit generates a trigger signal according to the starting current, and when the trigger signal is effective, the discharge unit is started to form an energy discharge path from the signal end to the ground so as to discharge ESD energy. The electrostatic protection circuit provided by the invention can be quickly started when ESD pulse occurs at the signal end, so that the internal circuit of the chip is prevented from being damaged. Meanwhile, the high-voltage capacitor is replaced by the coupling capacitor between the collector and the base of the triode or between the drain and the grid of the field effect transistor, and a mask layer arranged aiming at the high-voltage capacitor can be omitted during device design, so that the number of masks is reduced, the design cost of the circuit is further reduced, and the design efficiency of the circuit is improved.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.
It should be understood that in the following description, a "circuit" refers to a conductive loop formed by at least one element or sub-circuit through an electrical or electromagnetic connection. When an element or circuit is "connected to" another element or element/circuit is "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that no intervening elements are present between the two.
Fig. 2 is a schematic structural diagram of an electrostatic protection circuit according to an embodiment of the present invention. As shown in fig. 2, the electrostatic protection circuit 200 includes a trigger unit 230 and a bleeding unit 220 connected between the signal terminal 210 and ground.
Specifically, the trigger unit 230 includes at least one stage of a trigger circuit 231, a conversion circuit 232, and a first transistor 233. As shown in fig. 2, the first transistor 233 has a first terminal connected to the signal terminal 210 and a second terminal connected to an input terminal of the flip-flop circuit 231 connected thereto. The first transistor 233 is turned on by a parasitic capacitive coupling between a first terminal and a control terminal thereof to supply a start-up current to the trigger circuit 231. The trigger unit 230 further includes a first resistor R1, and the first resistor R1 is connected between the second terminal and the control terminal of the first transistor 233.
In addition, the trigger unit 230 includes stage 1 trigger circuits 231 to nth trigger circuits 231, N being a non-zero natural number. Each stage of the trigger circuit 231 includes an input terminal for receiving the start-up current or the output current of the previous stage of the trigger circuit 231, and an output terminal for providing the output current of the current stage. For example, the input terminal of the 1 st stage trigger circuit 231 receives the start current to generate the output current of the 1 st stage according to the start current, and the 2 nd to N th stage trigger circuits 231 generate the output currents of the 2 nd to N th stages according to the output currents of the 1 st to N-1 stage trigger circuits 231, respectively. The converting circuit 232 is connected to the nth stage trigger circuit 231, generates a trigger signal according to the output current of the nth stage, and the bleeding unit 220 bleeds energy from the signal terminal 210 according to the trigger signal.
In addition, in the embodiment of the present invention, the specific number N of stages of the trigger circuit 231 included in the trigger unit 230 is determined according to the starting current output by the first transistor and the starting voltage required by the bleeder unit, and when N is higher, the circuit is more complex, which increases the layout area and increases the cost, so that a person skilled in the art can select the number N of stages of the trigger circuit 231 included in the trigger unit 230 according to the specific circuit condition. In some implementations, the number of stages N is preferably 1 or 2.
In the following embodiments, the principle of the electrostatic protection circuit according to the present invention will be described by taking N equal to 1 as an example.
Fig. 3 shows a circuit diagram of an electrostatic protection circuit according to a first embodiment of the present invention. As shown in fig. 3, the first transistor 233 may be implemented by a transistor NPN1, a collector of the transistor NPN1 is connected to the signal terminal 210, a base is connected to a first terminal of the first resistor R1, an emitter is connected to a second terminal of the first resistor R1, and a node between the emitter of the transistor NPN1 and the first resistor R1 is used to provide a start-up current.
The trigger circuit 231 includes a transistor NPN2 and a second resistor R2, a collector of the transistor NPN2 is connected to the signal terminal 210, a base is connected to a node between an emitter of the transistor NPN1 and the first resistor R1 to receive the start-up current, and the emitter is used for providing the output current of the stage. A second resistor R2 is connected between the base and emitter of the transistor NPN 2.
In addition, the switching circuit 232 in fig. 1 may be implemented by a third resistor R3, a first end of the third resistor R3 is connected to a node between the emitter of the transistor NPN2 and the second resistor R2, and a second end of the third resistor R3 is grounded.
As shown in fig. 3, the bleeder unit 220 comprises a third transistor N3, a first terminal of the third transistor N3 is connected to the signal terminal 210, a second terminal thereof is grounded, and a control terminal thereof is connected to a first terminal of a third resistor for receiving the trigger signal.
When an ESD pulse occurs at the signal terminal 210, the voltage between the base and the emitter of the transistor NPN1 is raised by the first resistor R1 due to the parasitic capacitance coupling between the collector and the base of the transistor NPN1, so that the transistor NPN1 is turned on and provides a start-up current. The start-up current flows through the second resistor R2 in the trigger circuit 231, so that the voltage between the base and the emitter of the transistor NPN2 is higher than the turn-on voltage of the transistor NPN2, and the transistor NPN2 turns on and generates the output current of this stage. The output current provided by the transistor NPN2 flows through the third resistor R3, thereby generating a trigger signal at the first terminal of the third resistor R3, which raises the voltage of the control terminal of the third transistor N3, so that the third transistor N3 is turned on to form an energy discharge path from the signal terminal 210 to ground, thereby discharging the ESD energy from the signal terminal 210.
In addition, a diode D1 may be further included between the control terminal and the first terminal of the third transistor N3, an anode of the diode D1 is connected to the control terminal of the third transistor N3, and a cathode is connected to the first terminal of the third transistor N3, so as to prevent an overvoltage between the first terminal of the third transistor N1 and the ground.
Specifically, the third transistor N3 may be implemented by an N-type MOS transistor, where a control terminal of the third transistor N3 is a gate of the MOS transistor, a first terminal is a drain of the MOS transistor, and a second terminal is a source of the MOS transistor.
Fig. 4 is a schematic circuit diagram of an electrostatic protection circuit according to a second embodiment of the present invention, which is different from the electrostatic protection circuit according to the first embodiment shown in fig. 3 in that: the first transistor 233 is an N-type fet N1, a drain of the fet N1 is connected to the signal terminal 210, a gate thereof is connected to a first terminal of the first resistor R1, and a source thereof is connected to a second terminal of the first resistor R1 for providing a start-up current.
In addition, the structures and connection relations of the trigger circuit 231, the converting circuit 232, the diode D1 and the bleeding unit 220 are the same as those of the first embodiment shown in fig. 3, and are not described herein again.
In the second embodiment as shown in fig. 4, when the ESD pulse occurs at the signal terminal 210, the voltage between the gate and the source of the fet N1 is raised by the first resistor R1 due to the parasitic capacitance coupling between the drain and the gate of the fet N1, so that the fet N1 is turned on and provides the starting current. Then, a start current flows through the second resistor R2, so that the voltage between the base and the emitter of the transistor NPN2 is higher than the turn-on voltage of the transistor NPN2, and the transistor NPN2 turns on and provides the output current of the present stage. The output current provided by the transistor NPN2 flows through the third resistor R3, thereby generating a trigger signal at the first end of the third resistor R3, which raises the voltage of the gate of the third transistor N3, so that the third transistor N3 is turned on to form an energy discharge path from the signal terminal 210 to ground, thereby discharging the ESD energy from the signal terminal 210.
Fig. 5 shows a circuit schematic diagram of an electrostatic protection circuit according to a third embodiment of the present invention, and compared with the second embodiment shown in fig. 4, the electrostatic protection circuit according to the third embodiment of the present invention is different in that the trigger circuit 231 includes an N-type fet N2 and a second resistor R2, a first end and a second end of the second resistor R2 are respectively connected to the gate and the source of the fet N2, the drain of the fet N2 is connected to the signal terminal 210, a first end of the second resistor R2 is connected to a second end of the first resistor R1 to receive the start current, so that the second resistor R2 can provide the gate-source voltage of the fet N2 to control the on and off of the fet N2 according to the start current, and the source of the fet N2 provides the output current of this stage.
In addition, the structures and connection relations of the first transistor 233, the first resistor R1, the converting circuit 232, the diode D1 and the bleeding unit 220 are the same as those of the second embodiment shown in fig. 4, and are not repeated herein.
In the third embodiment as shown in fig. 5, when the ESD pulse occurs at the signal terminal 210, the gate-source voltage of the fet N1 is raised by the first resistor R1 due to the parasitic capacitance coupling between the drain and the gate of the fet N1, so that the fet N1 is turned on and generates a start-up current. The starting current flows through the second resistor R2, so that the gate-source voltage of the fet N2 is raised to the turn-on voltage of the fet N2, and the fet N2 turns on and generates the output current of the stage. The output current provided by the fet N2 flows through the third resistor R3, thereby generating a trigger signal at the first end of the third resistor R3, which raises the gate voltage of the third transistor N3, so that the third transistor N3 is turned on to form an energy discharge path from the signal terminal 210 to ground, thereby discharging the ESD energy from the signal terminal 210.
In summary, the ESD protection circuit provided by the present invention utilizes a coupling capacitor between a collector and a base of a triode or a drain and a gate of a field effect transistor to replace a high voltage capacitor to generate a start current, the trigger unit generates a trigger signal according to the start current, and when the trigger signal is valid, the discharge unit is turned on to form an energy discharge path from a signal terminal to ground, so as to discharge ESD energy. The electrostatic protection circuit provided by the invention can be quickly started when ESD pulse occurs at the signal end, so that the internal circuit of the chip is prevented from being damaged. Meanwhile, the high-voltage capacitor is replaced by the coupling capacitor between the collector and the base of the triode or between the drain and the grid of the field effect transistor, and a mask layer arranged aiming at the high-voltage capacitor can be omitted during device design, so that the number of masks is reduced, the design cost of the circuit is further reduced, and the design efficiency of the circuit is improved.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.