Electrostatic discharge circuit

Abstract

The invention provides an electrostatic discharge circuit. The electrostatic discharge circuit comprises a discharge switch, a first trigger circuit and a second trigger circuit, the discharge switch comprises a first end, a second end and a control end. The first end is coupled to a first power domain of the integrated circuit, and the second end is coupled to a second power domain of the integrated circuit, so that the first end is at a high level relative to the second end. The first trigger circuit is coupled between the first end and the control end and comprises a capacitor. The second trigger circuit is coupled between the second end and the control end, and when electrostatic discharge voltage occurs in the first power domain, the second trigger circuit is used for forming conduction voltage between the second end and the control end to conduct the discharge switch. When the electrostatic discharge voltage occurs in the second power domain, the second trigger circuit is used for short-circuiting the second end and the control end so as to turn on the discharge switch through the electrostatic discharge voltage.

Description

Technical Field

[0001] The present disclosure relates to electrostatic discharge protection technology, and more particularly to an electrostatic discharge circuit. Background Art

[0002] In the design of integrated circuits, due to the factors of human body discharge or machine discharge, the voltage and current caused by electrostatic discharge (ElectroStatic Discharge) can easily cause damage to the internal circuit. Therefore, an electrostatic discharge circuit needs to be set in the integrated circuit to achieve the purpose of electrostatic protection. Summary of the invention

[0003] The present disclosure relates to an electrostatic discharge circuit, comprising a discharge switch, a first trigger circuit and a second trigger circuit. The discharge switch comprises a first end, a second end and a control end. The first end is coupled to a first power domain of an integrated circuit, and the second end is coupled to a second power domain of the integrated circuit, so that the first end is at a high level relative to the second end. The first trigger circuit is coupled between the first end and the control end, and comprises a capacitor. The second trigger circuit is coupled between the second end and the control end, wherein when an electrostatic discharge voltage appears in the first power domain, the second trigger circuit is used to form a conduction voltage between the second end and the control end to turn on the discharge switch. When an electrostatic discharge voltage appears in the second power domain, the second trigger circuit is used to short-circuit the second end and the control end to turn on the discharge switch through the electrostatic discharge voltage.

[0004] The present disclosure also relates to an electrostatic discharge circuit, comprising a discharge switch, a first trigger circuit and a second trigger circuit. The discharge switch comprises a first end, a second end and a control end. The first end is coupled to a first power domain of an integrated circuit, and the second end is coupled to a second power domain of the integrated circuit, so that the first end is at a high level relative to the second end. The first trigger circuit is coupled between the first end and the control end, and comprises a capacitor. The second trigger circuit is coupled between the second end and the control end, and comprises a trigger switch. When the levels of the first power domain and the second power domain do not exceed a preset range, the trigger switch is used to turn on according to the gate voltage to turn off the discharge switch. The trigger switch also comprises a unidirectional switch, and when an electrostatic discharge voltage appears in the second power domain, the second trigger circuit is used to short-circuit the second end and the control end through the unidirectional switch to turn on the discharge switch.

[0005] Depending on the location where the electrostatic discharge voltage is generated, the second trigger circuit will have different operating characteristics. When the electrostatic discharge voltage is generated in the first power domain, the second trigger circuit can use its own impedance to form a conduction voltage to turn on the discharge switch. When the electrostatic discharge voltage is generated in the second power domain, the second trigger circuit is used to form a short circuit and use the electrostatic discharge voltage to turn on the discharge switch in real time. Accordingly, the electrostatic discharge circuit will be able to have a bidirectional protection function. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 FIG. 4 is a schematic diagram of an application of an electrostatic discharge circuit according to some embodiments of the present disclosure.

[0007] Figure 2 is a schematic diagram of an electrostatic discharge circuit according to some embodiments of the present disclosure.

[0008] Figures 3A to 3C is a schematic diagram of an electrostatic discharge circuit according to some embodiments of the present disclosure.

[0009] Description of reference numerals:

[0010] 100: Electrostatic Discharge Circuit

[0011] 110: First trigger circuit

[0012] 120: Second trigger circuit

[0013] 121: Trigger switch

[0014] 122: One-way switch

[0015] 123: Trigger switch

[0016] 124: One-way switch

[0017] 130: Discharge switch

[0018] CX: Integrated Circuit

[0019] CA: First Circuit

[0020] CB: Second Circuit

[0021] VD: Control level

[0022] VS: Reference level

[0023] VC1: First power domain

[0024] VC2: Second power domain

[0025] C1: Capacitor

[0026] R1: Impedance element

[0027] D1: One-way switch DETAILED DESCRIPTION

[0028] The following will disclose multiple embodiments of the present invention with the accompanying drawings. For the purpose of clear description, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. That is, in some embodiments of the present invention, these practical details are not necessary. In addition, in order to simplify the drawings, some conventional structures and elements will be illustrated in a simple schematic manner in the drawings.

[0029] In this document, when an element is referred to as "connected" or "coupled", it may refer to "electrical connection" or "electrical coupling". "Connected" or "coupled" may also be used to indicate the coordinated operation or interaction between two or more elements. In addition, although the terms "first", "second", etc. are used in this document to describe different elements, the terms are only used to distinguish between elements or operations described in the same technical terms. Unless the context clearly indicates otherwise, the terms do not specifically refer to or imply an order or sequence, nor are they used to limit the present invention.

[0030] Figure 1 The application diagram of the electrostatic discharge circuit 100 according to some embodiments of the present disclosure is shown. In one embodiment, the electrostatic discharge circuit 100 is applied to the integrated circuit CX to eliminate the electrostatic discharge phenomenon. For example, when an electrostatic discharge voltage appears in the integrated circuit CX, the electrostatic discharge voltage will preferentially pass through the electrostatic discharge circuit 100 and will not be conducted to the computing circuit in the integrated circuit CX to prevent the computing function of the integrated circuit CX from being damaged. Since the principle of electrostatic discharge (Electro Static Discharge) can be understood by people in this field, it will not be further described here.

[0031] The integrated circuit CX has a plurality of different power domains, that is, a plurality of different circuits in the integrated circuit CX may operate at different voltages. Figure 1 As shown, the operating voltage of the first circuit CA during operation may be 20 volts, and the operating voltage of the second circuit CB during operation may be 10 volts. In this case, the first circuit CA and the second circuit CB belong to different power domains in the integrated circuit CX. When an electrostatic discharge phenomenon occurs, the electrostatic discharge circuit 100 needs to be used as a path for discharging voltage or current. In a normal state (i.e., no electrostatic discharge phenomenon occurs), the electrostatic discharge circuit 100 cannot be turned on due to the voltage difference between different power domains, otherwise it will cause signal errors between the circuits CA and CB.

[0032] Figure 2 FIG. 1 is a schematic diagram of an electrostatic discharge circuit 100 according to some embodiments of the present disclosure. The electrostatic discharge circuit 100 includes a first trigger circuit 110, a second trigger circuit 120, and a discharge switch 130. The electrostatic discharge circuit 100 is disposed in an integrated circuit CX (such as Figure 1 When an electrostatic discharge voltage is generated in the first power domain VC1 or the second power domain VC2, the discharge switch 130 is turned on by the first trigger circuit 110 or the second trigger circuit 120 to form a path for discharging voltage or current.

[0033] The discharge switch 130 includes a first terminal, a second terminal, and a control terminal. The first terminal of the discharge switch 130 is coupled to the first power domain VC1, and the second terminal of the discharge switch 130 is coupled to the second power domain VC2, so that the first terminal of the discharge switch 130 is at a high level relative to the second terminal of the discharge switch 130. In other words, when the integrated circuit CX operates normally (i.e., when no electrostatic discharge voltage is generated), the voltage on the first terminal of the discharge switch 130 is greater than the voltage on the second terminal of the discharge switch 130. In some embodiments, the discharge switch 130 is a metal oxide semiconductor field effect transistor, and its base is coupled to a reference level VS (e.g., a ground level), but the present disclosure is not limited thereto.

[0034] The first trigger circuit 110 is coupled between the first end (i.e., the node coupled to the first power domain VC1) and the control end (e.g., the gate) of the discharge switch 130, and includes at least a capacitor C1. The first trigger circuit 110 is used to turn on the discharge switch 130 when an electrostatic discharge voltage appears in the first power domain VC1, so that an electrostatic discharge path is formed on the discharge switch 130.

[0035] The second trigger circuit 120 is coupled between the second end (i.e., the node coupled to the second power domain VC2) and the control end (e.g., the gate) of the discharge switch 130. The second trigger circuit 120 is used to turn on the discharge switch 130 when an electrostatic discharge voltage appears in the second power domain VC2, so that an electrostatic discharge path is formed on the discharge switch 130.

[0036] Here, the operation of the electrostatic discharge circuit 100 is described: when the circuits in the first power domain VC1 and the second power domain VC2 operate normally, the levels of the first power domain VC1 and the second power domain VC2 will not exceed the preset range. Since the first power domain VC1 is at a high level relative to the second power domain VC2, the capacitor C1 will be gradually charged until the stored electrical energy is equal to the level difference between the first power domain VC1 and the second power domain VC2. At the same time, the second trigger circuit 120 is used to control the voltage of the control end so that the discharge switch 130 remains turned off. Specifically, the second trigger circuit 120 will continue to pull down (pull low) the voltage of the control end of the discharge switch 130 to ensure that the voltage of the control end of the discharge switch 130 is a disable level (e.g., a low level). Therefore, the discharge switch 130 will remain in the off state to ensure that there is no leakage between the first power domain VC1 and the second power domain VC2.

[0037] When an electrostatic discharge voltage appears in the first power domain VC1, the first trigger circuit 110 will instantly raise the control terminal of the discharge switch 130 to a high level due to the capacitive coupling effect of the capacitor C1. At this time, because the second trigger circuit 120 does not have time to pull down the voltage of the control terminal of the discharge switch 130, the equivalent impedance of the second trigger circuit 120 itself will form a conduction voltage between the second terminal and the control terminal of the discharge switch 130. In other words, the voltage difference between the control terminal and the second terminal of the discharge switch 130 will be greater than the threshold voltage value of the discharge switch 130, so the discharge switch 130 will be turned on.

[0038] On the other hand, when an electrostatic discharge voltage appears in the second power domain VC2, the second trigger circuit 120 is used to short-circuit the second end and the control end of the discharge switch 130. At this time, because the voltage of the control end of the discharge switch 130 will be instantly pulled up to the high level of the electrostatic discharge voltage (i.e., the enabling level), the discharge switch 130 will be turned on.

[0039] Figures 3A to 3C is a schematic diagram of an electrostatic discharge circuit 100 according to some embodiments of the present disclosure. Figures 3A to 3C In the figure, different implementations of the second trigger circuit 120 are described respectively. Figures 3A to 3C In, with Figure 2 Similar elements related to the embodiments of the present invention are denoted by the same reference numerals for easy understanding, and the specific principles of similar elements have been described in detail in the previous paragraphs. Figures 3A to 3C The components have a cooperative operation relationship and need to be introduced, which will not be repeated here.

[0040] like Figure 3A As shown, in one embodiment, the second trigger circuit 120 includes an impedance element R1 and a unidirectional switch D1. The impedance element R1 and the unidirectional switch D1 are connected in parallel. When an electrostatic discharge voltage appears in the first power domain VC1, causing the control end of the discharge switch 130 to be instantly pulled up to a high level, the equivalent impedance of the impedance element R1 will form a turn-on voltage between the second end and the control end of the discharge switch 130 (that is, the cross voltage of the impedance element R1 will be greater than the threshold voltage of the discharge switch 130) to turn on the discharge switch 130.

[0041] When an ESD voltage appears in the second power domain VC2, the unidirectional switch D1 will be turned on to form a short circuit, so that the voltage at the control end of the discharge switch 130 is instantly pulled up to the high level of the ESD voltage to turn on the discharge switch 130. In some embodiments, the unidirectional switch D1 can be a diode.

[0042] Depending on the location where the electrostatic discharge voltage is generated, the second trigger circuit 120 will have different operating characteristics. When the electrostatic discharge voltage appears in the first power domain VC1, the second trigger circuit 120 will form a turn-on voltage due to its own equivalent impedance, so that the discharge switch 130 is turned on. Conversely, when the electrostatic discharge voltage appears in the second power domain VC2, the second trigger circuit 120 can form a short circuit to use the electrostatic discharge voltage to turn on the discharge switch 130 in real time. Accordingly, the electrostatic discharge circuit 100 will have a bidirectional protection function.

[0043] Figure 3B FIG. 1 is another embodiment of the second trigger circuit 120. In one embodiment, the second trigger circuit 120 includes a trigger switch 121, which may be an N-type metal oxide semiconductor field effect transistor, but the present disclosure is not limited thereto. The control end of the trigger switch 121 is coupled to the control level VD. When the integrated circuit CX does not have an electrostatic discharge voltage (i.e., the levels of the first power domain VC1 and the second power domain VC2 do not exceed a preset range), the trigger switch 121 will be turned on according to the gate voltage formed on the gate of the trigger switch 121 by the control level VD. At this time, the trigger switch 121 can be regarded as Figure 3A The impedance element R1 is thus reduced, and thus the discharge switch 130 remains in the off state.

[0044] The gate voltage provided by the control level VD is an enabling level for the trigger switch 121. In some embodiments, the control end of the trigger switch 121 can be connected to the first end of the discharge switch 130 to use the high level of the first power domain VC1 as the gate voltage.

[0045] In one embodiment, the trigger switch 121 further includes a unidirectional switch 122. When an electrostatic discharge voltage appears in the second power domain VC2, the second trigger circuit 120 is used to short-circuit the second end and the control end of the discharge switch 130 through the unidirectional switch 122 to turn on the discharge switch 130.

[0046] In this embodiment, the unidirectional switch 122 may be a parasitic diode in the trigger switch 121. For example, the trigger switch 121 is an N-type metal oxide semiconductor field effect transistor, and the source is coupled to the second end of the discharge switch 130. The source of the trigger switch 121 is also short-circuited with the base to form a parasitic diode (unidirectional switch 122) between the source and the drain. However, the present disclosure is not limited to this. In other embodiments, the unidirectional switch 122 may also be a diode connected in parallel with the trigger switch 121.

[0047] When the first power domain VC1 has an electrostatic discharge voltage, the unidirectional switch 122 will not be turned on, and the equivalent impedance of the trigger switch 121 will form a turn-on voltage between the second end and the control end of the discharge switch 130 (i.e., the voltage across the trigger switch 121 will be greater than the threshold voltage of the discharge switch 130) to turn on the discharge switch 130. At this time, the trigger switch 121 operates as follows: Figure 3A The impedance element R1.

[0048] When the second power domain VC2 has an electrostatic discharge voltage, the unidirectional switch 122 of the second trigger circuit 120 will be turned on to form a short circuit, so that the voltage at the control end of the discharge switch 130 is instantly pulled up to the high level of the electrostatic discharge voltage to turn on the discharge switch 130. At this time, the second trigger circuit 120 operates as follows: Figure 3A The one-way switch D1.

[0049] In some embodiments, the trigger switch 121 is always kept in an off state according to the gate voltage provided by the control level VD. However, in other embodiments, the trigger switch 121 may also receive a disable signal to form an off state when an abnormal situation occurs in the integrated circuit, so as to increase the equivalent impedance of the second trigger circuit 120.

[0050] Figure 3C FIG. 1 is another embodiment of the second trigger circuit 120. In one embodiment, the second trigger circuit 120 also includes a trigger switch 123, but the trigger switch 123 is a P-type metal oxide semiconductor field effect transistor. The control end of the trigger switch 123 is coupled to the reference level VS (e.g., a low level) to keep the trigger switch 123 in the on state. In other embodiments, the control end of the trigger switch 123 can also be connected to the second end of the discharge switch 130 to use the level of the second power domain VC2 as the gate voltage of the control end of the trigger switch 123.

[0051] The drain of the trigger switch 123 is coupled to the second end of the discharge switch 130, and the source and base of the trigger switch 123 are short-circuited to form a parasitic diode between the source and the drain, namely, the unidirectional switch 124. Figure 3B The embodiments are the same as those of the present invention, so they will not be described in detail here.

[0052] In addition, in some embodiments, the threshold voltage value of the trigger switch 123 is smaller than the threshold voltage value of the discharge switch 130, so as to ensure that when the levels of the first power domain VC1 and the second power domain VC2 are within a preset range, the trigger switch 123 is turned on, but the voltage at the control end of the discharge switch 130 does not cause the discharge switch 130 to be turned on.

[0053] The various elements, method steps or technical features in the aforementioned embodiments may be combined with each other without being limited to the order of textual description or the order of presentation of the drawings in the present disclosure.

[0054] Although the present disclosure has been disclosed in the above-mentioned implementation mode, it is not intended to limit the present disclosure. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the scope of the attached claims.

Claims

1. An electrostatic discharge circuit, comprising: A discharge switch, comprising a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to a first power domain of an integrated circuit, and the second terminal is coupled to a second power domain of the integrated circuit, so that the first terminal is at a high level relative to the second terminal; a first trigger circuit coupled between the first terminal and the control terminal and comprising a capacitor; and a second trigger circuit coupled between the second terminal and the control terminal, wherein when an electrostatic discharge voltage appears in the first power domain, the second trigger circuit is used to form a conduction voltage between the second terminal and the control terminal to turn on the discharge switch; When an electrostatic discharge voltage appears in the second power domain, the second trigger circuit is used to short-circuit the second terminal and the control terminal so as to turn on the discharge switch through the electrostatic discharge voltage. 2 . The electrostatic discharge circuit according to claim 1 , wherein the second trigger circuit comprises an impedance element and a unidirectional switch, and the impedance element and the unidirectional switch are connected in parallel. The electrostatic discharge circuit according to claim 2 , wherein the unidirectional switch is a diode.

4. The electrostatic discharge circuit according to claim 1, wherein when the levels of the first power domain and the second power domain do not exceed a preset range, the second trigger circuit is used to control the voltage of the control terminal so that the discharge switch remains turned off.

5. An electrostatic discharge circuit, comprising: A discharge switch, comprising a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to a first power domain of an integrated circuit, and the second terminal is coupled to a second power domain of the integrated circuit, so that the first terminal is at a high level relative to the second terminal; a first trigger circuit coupled between the first terminal and the control terminal and comprising a capacitor; and a second trigger circuit coupled between the second terminal and the control terminal, and comprising a trigger switch, wherein when the levels of the first power domain and the second power domain do not exceed a preset range, the trigger switch is used to be turned on according to a gate voltage to turn off the discharge switch; The trigger switch further includes a unidirectional switch. When an electrostatic discharge voltage appears in the second power domain, the second trigger circuit is used to short-circuit the second end and the control end through the unidirectional switch to turn on the discharge switch. 6 . The electrostatic discharge circuit as claimed in claim 5 , wherein the unidirectional switch is a parasitic diode in the trigger switch.

7. The electrostatic discharge circuit according to claim 6, wherein the trigger switch is a metal oxide semiconductor field effect transistor, a source of the trigger switch is coupled to the second end, and the source and a base of the trigger switch are short-circuited to form the unidirectional switch in the trigger switch.

8. The electrostatic discharge circuit according to claim 6, wherein the trigger switch is a metal oxide semiconductor field effect transistor, a drain of the trigger switch is coupled to the second end, and a source and a base of the trigger switch are short-circuited to form the unidirectional switch in the trigger switch. 9 . The electrostatic discharge circuit as claimed in claim 8 , wherein a threshold voltage value of the trigger switch is smaller than a threshold voltage value of the discharge switch. 10 . The electrostatic discharge circuit of claim 5 , wherein when an electrostatic discharge voltage appears in the first power domain, an equivalent impedance of the trigger switch is used to form a turn-on voltage between the second terminal and the control terminal to turn on the discharge switch.

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