# Patent

## Title
ESD detection circuit

## Abstract

An ESD detection circuit which includes: a triggering circuit for generating an ESD trigger signal when the ESD detection circuit is in ESD mode; a bias circuit for providing at least a first bias voltage and a second bias voltage for controlling the operation of the triggering circuit; a trigger controlling circuit for decreasing a voltage difference between the first bias voltage and the second bias voltage when the ESD detection circuit is in the ESD mode, and for controlling a duration of the ESD trigger signal that is generated by the triggering circuit; and an activating control circuit for activating the trigger controlling circuit and the triggering circuit to enter the ESD mode according to a voltage level at a first node.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ESD (electrostatic discharge) detection circuit and related method, and more particularly, to an ESD detection circuit and related method capable of reducing a size of the ESD detection circuit itself and extending a duration of discharge.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram of a prior art ESD protection circuit 10. The ESD protection circuit 10 includes a low-pass filter 11 having a resistor R and a capacitor C, an inverter 12, and an ESD Clamp Circuit 13. The inverter 12 is composed of a P-type field effect transistor (FET) MP and a N-type FET MN. When an electrostatic signal Sesd rises at a first node Na of the ESD protection circuit 10, a voltage level at a second node Nb is temporarily maintained at a lower level because of the low-pass filter 11. The P-type FET MP is turned on and the N-type FET MN is turned off. Accordingly, through the P-type FET MP, the electrostatic signal Sesd is converted into a current signal I_trig, which is utilized for triggering the ESD clamp circuit 13 to perform a discharge operation upon the electrostatic signal Sesd at the first node Na. However, when the voltage level at the first node Na is higher than that of a normal supply voltage VDD (e.g. the voltage level at the first node Na equals 3*VDD), gate-oxide layers of the capacitor C, the P-type FET MP, and the N-type FET MN will be damaged since voltage drops across the gate-oxide layers will become much larger. In summary, the ESD protection circuit 10 cannot absorb the electrostatic signal Sesd which has greater voltage amplitudes. Further description is detailed in US patent application pub. No. 20030076636A1.
In addition, according to U.S. Pat. No. 5,956,219, another ESD protection circuit is disclosed. Although the ESD protection circuit is able to absorb an electrostatic signal having greater voltage amplitudes, this ESD protection circuit implemented by a triple well process has some disadvantages. The ESD protection circuit increases cost of production and complicates the gate-driven technique, especially when an advanced nano-scale CMOS (Complementary Metal-Oxide-Semiconductor) process is applied.
Additionally, according to U.S. Pat. No. 6,954,098, an ESD protection circuit is further disclosed. Similarly, the ESD protection circuit is also capable of absorbing an electrostatic signal having greater voltage amplitudes. In addition to a normal supply voltage, however, this ESD protection circuit further requires a lower supply voltage for proper operation. If either one of the normal or lower supply voltages is not provided, gate-oxide layers of FETs within the ESD protection circuit could be damaged. Consequently, in order to avoid the above-mentioned problems, the ESD protection circuit disclosed by U.S. Pat. No. 6,954,098 is usually implemented by the thicker gate-oxide layer process technique, subsequently increasing cost of production.
SUMMARY OF THE INVENTION
It is therefore one of the objectives of the present invention to provide an ESD detection circuit and related method, to solve the above-mentioned problems.
According to an embodiment of the claimed invention, an ESD detection circuit is disclosed. The ESD detection circuit is coupled between a first node and a second node, and the ESD detection circuit comprises a triggering circuit, a bias circuit, a trigger controlling circuit, and an activating control circuit. The triggering circuit is utilized for generating an ESD trigger signal when the ESD detection circuit is in ESD mode. The bias circuit is coupled to the triggering circuit and utilized for providing at least a first bias voltage and a second bias voltage to control the operation of the triggering circuit. The trigger controlling circuit is coupled to the bias circuit and the triggering circuit, and the trigger controlling circuit is utilized for decreasing a voltage difference between the first bias voltage and the second bias voltage when the ESD detection circuit is in the ESD mode, to control a duration of the ESD trigger signal generated by the triggering circuit. The activating control circuit is coupled to the trigger controlling circuit and the trigger circuit, and it is utilized for activating the trigger controlling circuit and the triggering circuit to enter the ESD mode according to a voltage level at the first node.
According to another embodiment of the claimed invention, a method for generating an ESD trigger signal corresponding to a first node and a second node is disclosed. The method comprises: activating an ESD mode according to a voltage level at the first node; providing a trigger circuit and utilizing the trigger circuit to generate the ESD trigger signal in the ESD mode; providing at least a first bias voltage and a second bias voltage to control an operation of the trigger circuit; and decreasing a voltage difference between the first bias voltage and the second bias voltage in the ESD mode, for controlling a duration of the ESD trigger signal.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a prior art ESD protection circuit.
FIG. 2 is a diagram of an ESD detection circuit according to an embodiment of the present invention.
FIG. 3 is a chart showing the electrostatic signal SESD, the first bias voltage V1, the second bias voltage V2, and voltage levels at the nodes Nb, N3, N4, N5, and N6 when the ESD detection circuit shown in FIG. 2 operates in the ESD mode.
FIG. 4 is a flowchart illustrating an operation of the ESD detection circuit shown in FIG. 2.



DETAILED DESCRIPTION
Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.
Please refer to FIG. 2. FIG. 2 is a diagram of an ESD detection circuit 100 according to an embodiment of the present invention. The ESD detection circuit 100 includes a triggering circuit 101, a bias circuit 102, a trigger controlling circuit 103, and an activating control circuit 104. The ESD detection circuit 100 is coupled between a first node NVDD and a second node NGND. The triggering circuit 101 is utilized for generating an ESD trigger signal Strigger when the ESD detection circuit 100 is in ESD mode. The bias circuit 102 is coupled to the triggering circuit 101 and utilized for providing a first bias voltage V1, a second bias voltage V2, and a third bias voltage V3, for controlling the operation of the triggering circuit 101. The trigger controlling circuit 103 is coupled to the bias circuit 102 and the triggering circuit 01 ; the trigger controlling circuit 103 is utilized for decreasing a voltage difference Vdiff between the first bias voltage V1 and the second bias voltage V2 in the ESD mode, to control a duration Ttrigger of the ESD trigger signal Strigger, which is generated by the triggering circuit 101. The activating control circuit 104 is coupled to the trigger controlling circuit 103 and the triggering circuit 101. The activating control circuit 104 is utilized for activating the trigger controlling circuit 103 and triggering circuit 101 to enter the ESD mode according to a voltage level VDD at the first node NVDD. Please note that, in order to describe the spirit of the ESD detection circuit 100 disclosed in this embodiment more clearly, an ESD clamp circuit 105 is further coupled to the first node NVDD, the second node NGND, and the triggering circuit 101. The ESD clamp circuit 105 is used for performing a discharge operation upon the voltage at the first node NVDD according to the ESD trigger signal Strigger. Specifically, the ESD clamp circuit 105 includes a PNP BJT (bipolar junction transistor) 1051, an NPN BJT 1052, a N-well resistor 1053, a P-well resistor 1054, and a plurality of diodes 1055. The configuration of the ESD clamp circuit 105 is shown in FIG. 2 but is not detailed for the sake of brevity.
As shown in FIG. 2, the bias circuit 102 is coupled between the first node NVDD and the second node NGND. The bias circuit 102 includes a plurality of P-type FETs Md1, Md2, Md3, Md4, Md5, and Md6 with a first, second, third, fourth, fifth, and sixth diode-connected configurations, respectively. These diode-connected P-type FETs Md1, Md2, Md3, Md4, Md5, and Md6 are connected between the first node NVDD and the second node NGND in a cascading arrangement, and they are utilized for generating the first bias voltage V1, the second bias voltage V2, and the third bias voltage V3, according to the voltage levels (i.e. VDD and VGND) at the first node NVDD and second node NGND. In the bias circuit 102, not all base terminals of the diode-connected FETs are coupled to source terminals of the same diode-connected FETs: the base terminals of the first and second P-type FETs Md1 and Md2 are coupled to the first node NVDD, the base terminals of the third and fourth P-type FETs Md3 and Md4 are coupled to the first bias voltage V1, and the base terminals of the fifth and sixth P-type FETs Md5 and Md6 are coupled to the second bias voltage V2. The activating control circuit 104 includes a resistor R1 and a capacitor MC1. The resistor R1 is serially connected to the first node NVDD and a first terminal Nb of the capacitor MC1.
The trigger controlling circuit 103 includes a first P-type FET M1, a second P-type FET M2, a third P-type FET M3, a first switching FET Ms1, a second switching FET Ms2, and a voltage level controlling circuit 1031. The P-type FET M1 has a source terminal coupled to the first node NVDD and a gate terminal coupled to the first terminal Nb of the capacitor Mc1. The second P-type FET M2 has a source terminal coupled to a drain terminal (i.e. N1) of the first P-type FET M1 and a gate terminal (i.e. N2) coupled to the first bias voltage V1. The third P-type FET M3 has a source terminal coupled to a drain terminal (i.e. N3) of the second FET M2, a gate terminal (i.e. a node N4) coupled to the second bias voltage V2, and a drain terminal Ndm3 coupled to the second node NGND. The first switching P-type FET Ms1 has a drain terminal (i.e. N2) coupled to the bias voltage V1 and the activating control circuit 104, a source terminal coupled to the triggering circuit 101 (i.e. N5), and a gate terminal coupled to the drain terminal (i.e. N3) of the second P-type FET M2. The second switching P-type FET Ms2 has a drain terminal (i.e. N4) coupled to the second bias voltage V2, a source terminal coupled to a node N6 of the triggering circuit 101, and a gate terminal (i.e. N7) coupled to the third bias voltage. Additionally, the voltage level controlling circuit 1031 is coupled between the drain terminals of the first switching P-type FET Ms1 and second switching P-type FET Ms2. The voltage level controlling circuit 1031 is utilized for decreasing the voltage difference Vdiff between the first bias voltage V1 and second bias voltage V2 according to a voltage level Vr at the drain terminal of the second P-type FET M2 when the ESD detection circuit 100 is in the ESD mode. In this embodiment, the voltage level controlling circuit 1031 includes a first inverter 10311 and a fourth P-type FET M4; the first inverter 10311 is comprised of a P-type FET and a N-type FET (as shown in FIG. 2). The first inverter 10311 has a first reference node coupled to the gate terminal (i.e. N2) of the second P-type FET M2, a second reference node coupled to the gate terminal (i.e. N4) of the third P-type FET M3, and an input node coupled to the drain terminal of the second P-type FET M2. The fourth P-type FET M4 has a source terminal coupled to the gate terminal of the second P-type FET M2, a drain terminal coupled to the gate terminal of the third P-type FET M3, and a gate terminal coupled to an output node N8 of the first inverter 10311.
The triggering circuit 101 includes a fifth P-type FET M5, a sixth P-type FET M6, and a second inverter 1011. The fifth P-type FET M5 has a source terminal coupled to the first node NVDD, a gate terminal coupled to the first terminal Nb of the capacitor Mc1, and a drain terminal coupled to the source terminal (i.e. N5) of the first switching P-type FET Ms1. The sixth P-type FET M6 has a source terminal coupled to the drain terminal of the fifth P-type FET M5 and source terminal of the first switching P-type FET Ms1, a gate terminal coupled to the drain terminal (i.e. N2) of the first switching p-type FET Ms1, and a drain terminal (i.e. N6) coupled to the source terminal of the second switching P-type FET Ms2. The second inverter 1011 is comprised of a P-type FET and a N-type FET (as shown in FIG. 2). The second inverter 1011 has a first reference node coupled to the drain terminal of the sixth P-type FET M6, a second reference node coupled to the second node NGND, an input node coupled to the drain terminal of the second switching P-type FET Ms2, and an output node N10 utilized for outputting the ESD trigger signal Strigger.
In this embodiment, the ESD detection circuit 100 can operate under two modes (the ESD mode and a normal mode). When the ESD detection circuit 100 operates in the normal mode, the N-type FET in the second inverter 1011 is utilized for maintaining a voltage level of the output node N10 at the ground level VGND, and the first node NVDD is coupled to a supply voltage VDD. In order to describe the spirit of the present invention more clearly, it is assumed that the ground level VGND and the supply voltage VDD equal zero and 3.3 volts respectively. Therefore, in normal mode, the first bias voltage V1, the second bias voltage V2, and the third bias voltage V3 are respectively equal to 2.2 volts, 1.1 volts, and 0.6 volts. Please note that, since the base terminal of the P-type FET Md6 is coupled to the node N4, there exists a body effect in the P-type FET Md6. The third bias voltage V3 thus becomes 0.6 volts, and the second switching FET Ms2 is turned on because of the third bias voltage V3. As shown in FIG. 2, due to the second bias voltage V2, a voltage level at the node N6 is charged through the second switching FET Ms2 until the voltage level at the node N6 equals 1.1 volts. Since a voltage difference across the source-drain terminals of the P-type FET in the second inverter 1011 is zero, this P-type FET is turned off. Accordingly, in normal mode, the ESD detection circuit 100 does not generate the ESD trigger signal Strigger, and the ESD clamp circuit 105 is not enabled. Additionally, the N-type FET in the second inverter 1011 is turned on, so the phase margin of the ESD detection circuit 100 is widened for ensuring that the trigger controlling circuit 103 does not trigger the ESD clamp circuit 105 in normal mode.
Moreover, since the first P-type FET M1 and fifth P-type FET M5 are biased by the supply voltage VDD equaling 3.3 volts, the first P-type FET M1 and fifth P-type FET M5 are turned off. In other words, in normal mode, a current path composed of the P-type FETs M1, M2, and M3 is not conductive, and the P-type FET M2 is turned off. That is to say, a voltage drop across the source-gate terminals of the P-type FET M2 is lower than the threshold voltage |Vtp| (i.e. 1.2 volts) of a common P-type FET. Therefore, the voltage level at the node N1 is maintained between 2.2 volts and 2.2 volts plus the threshold voltage |Vtp|. Similarly, the P-type FET M3 is also turned off, and the voltage level at the node N3 is maintained between 1.1 volts and 1.1 volts plus the threshold voltage |Vtp|. When the P-type FET of the first inverter 10311 and the first switching FET Ms1 are turned on, the voltage levels at the nodes N2 and N5 are equal to 2.2 volts. The voltage drops at the source-gate terminals of the N-type FET of the first inverter 10311, the fourth P-type FET M4, and the sixth P-type FET M6 are approximately equal to zero so that they are turned off. As mentioned above, in this embodiment, when the ESD detection circuit 100 operates in normal mode and the supply voltage VDD is equal to 3.3 volts, all FETs having voltage drops equal to 1.2 volts across their gate-oxide layers can operate correctly.
On the other hand, when the ESD protection circuit 100 is not in normal mode, the supply voltage VDD at the first node NVDD is equal to zero. However, when the electrostatic signal SDD is introduced at the first node NVDD (e.g. the power of the supply voltage VDD is enabled instantaneously), an impulse signal will occur immediately at the voltage level of the first node NVDD. A peak value of the impulse signal is usually higher than the supply voltage VDD (i.e. 3.3 volts) in normal mode. This will cause a circuitry coupled to the supply voltage VDD to be damaged. In order to describe the spirit of the present invention more clearly, in this embodiment, a peak value of the electrostatic signal SESD is assumed to equal 6 volts for illustrative purposes. That is, when the power of the supply voltage VDD is enabled instantaneously, the voltage level of the electrostatic signal SESD at the first node NVDD rises from zero to 6 volts rapidly (as shown in FIG. 3). FIG. 3 is a chart showing the electrostatic signal SESD, the first bias voltage V1, the second bias voltage V2, and voltage levels (i.e. Vnb, Vn3, Vn4, Vn5, and Vn6) at the nodes Nb, N3, N4, N5, and N6 when the ESD detection circuit 100 shown in FIG. 2 operates in the ESD mode. When the electrostatic signal SESD rises and reaches 6 volts at timing t1, the voltage level Vnb at the first node Nb rises more slowly than the electrostatic signal SESD since the activating control circuit 104 is an RC low-pass filter. This will cause a voltage drop across the first node NVDD and the first node Nb. The P-type FET M1 and M5 are therefore turned on, and the nodes N1 and N5 are charged so that the voltage levels Vn1 and Vn5 at the nodes N1 and N5 raise rapidly. Since the first bias voltage V1, the second bias voltage V2, and the third bias voltage V3 at the nodes N2, N4, and N7 in the timing t0 are approximately equal to zero, the P-type FETs M2 and M3 are also turned on and the nodes N3 and N6 are charged when the electrostatic signal SESD is introduced. Rising values of the voltage levels Vn3 and Vn6 at the nodes N3 and N6 are substantially equal to those at the nodes N1 and N5. The second switching FET Ms2 is subsequently turned on. This is because the voltage level at node N7 still remains at a lower level than the voltage level Vn6 at node N6 even as the voltage level Vn6 is rising. Accordingly, the voltage level Vn4 at the node N4 is charged and then rises to equal voltage level Vn6. In practice, however, an RC delay caused by the turned-on resistance of the second switching FET Ms2 and parasitic capacitance at the node N4 will maintain the voltage level Vn4 of the node N4 at a lower voltage level, as shown in FIG. 3. Because of the lower voltage level, the second switching FET Ms2 will be continuously turned on when the electrostatic signal SESD occurs. Additionally, the voltage level Vn3 at the gate terminal (i.e. the node N3) of the P-type FET in the first inverter 10311 is higher that that (i.e. the voltage level Vn4) at the node N4. The N-type FET is therefore turned on so that the voltage level Vn8 at the node N8 is approximately equal to that (i.e. the voltage level Vn4) at the node N4. The P-type FET M4 is then turned on so that the first bias voltage V1 at the node N2 is forced to be near the second bias voltage V2 at the node N4. The voltage difference Vdiff between the first bias voltage V1 and second bias voltage V2 equals the threshold voltage |Vtp| of the P-type FET M4.
Additionally, when the ESD detection circuit 100 operates in the ESD mode, since a difference between the voltage levels at the gate and source terminals (i.e. the nodes N3 and N5) of the second switching FET Ms2 is very small so that the second switching FET Ms2 will be turned off. The first bias voltage V1 comes to a voltage level which is lower than the voltage level Vn5. As mentioned above, the voltage levels at the gate terminals (i.e. Nb and N2) of the P-type FETs M5 and M6 in the triggering circuit 101 and the voltage level at the gate terminal (i.e. N4) of the P-type FET in the second inverter 1011 can be maintained at lower levels. Thus, the electrostatic signal SESD is rapidly converted into the ESD trigger signal Strigger, which is transmitted to the node N10. It should be noted that those skilled in this art should understand that the ESD trigger signal Strigger is a current signal. Moreover, since the voltage level controlling circuit 1031 of the trigger controlling circuit 103 is a digital control circuit, a size of the trigger controlling circuit 103 can be considerably reduced and the leakage of electricity can also be decreased when the ESD detection circuit 100 operates in the normal mode. The operation of the ESD clamp circuit 105 should be understood by those skilled in this art; further description is not detailed for the sake of the brevity. Furthermore, it should be noted that the triggering circuit 101, the bias circuit 102, the trigger controlling circuit 103 and the activating control circuit 104 can be implemented by transistors having gate dielectrics where thickness of the gate dielectrics is substantially identical. This design modification also falls within the scope of the present invention.
Please refer to FIG. 4. FIG. 4 is a flowchart illustrating a method for generating an ESD trigger signal corresponding to a first node and a second node according to a second embodiment of the present invention. Since the method for generating the ESD trigger signal can be implemented with the ESD detection circuit 100 shown in FIG. 2, the flowchart in the following is detailed in conjunction with the ESD detection circuit 100 for describing the spirit of the method more clearly. Provided that substantially the same result is achieved, the steps of the flowchart shown in FIG. 4 need not be in the exact order shown and need not be contiguous; that is, other steps can be intermediate. The method includes the following steps:
Step 401: Start.
Step 402: Determine whether the ESD detection circuit 100 is in normal mode or in ESD mode. When the ESD detection circuit 100 operates under the normal mode, go to Step 403; otherwise, go to Step 406 when the ESD detection circuit 100 operates under the ESD mode.
Step 403: Utilize the bias circuit 102 to generate the first bias voltage V1, the second bias voltage V2, and the third bias voltage V3 according to the supply voltage VDD at the first node NVDD.
Step 404: Use the trigger controlling circuit 103 and activating control circuit 104 to disable the triggering circuit 101 according to the first bias voltage V1, the second bias voltage V2, and the third bias voltage V3.
Step 405: Disable the ESD clamp circuit 105.
Step 406: Use the activating control circuit 104 to enable the triggering circuit 101 for generating the ESD trigger signal Strigger to trigger the ESD clamp circuit 105.
Step 407: Utilize the trigger controlling circuit 103 to force the first bias voltage V1 at the node N2 to be near to the second bias voltage V2 at the node N4 for extending the duration Ttrigger of the ESD trigger signal Strigger.
Step 408: Use the ESD clamp circuit 105 to rapidly discharge the electrostatic signal SESD at the first node NVDD.
It should be noted that in Step 402, the supply voltage VDD at the first node NVDD is equal to zero while the ESD detection circuit 100 in not the normal mode. In other words, when the electrostatic signal SESD rises at the first node NVDD, the voltage level at the first node NVDD is initially also equal to zero. Therefore, in Step 407, the trigger controlling circuit 103 will force the first bias voltage V1 at node N2 to be near zero (at node N4). Additionally, the trigger controlling circuit 103 also utilizes the voltage level controlling circuit 1031 to control the P-type FET M4 for forcing the first bias voltage V1 at the node N2 to be near the second bias voltage V2 at the node N4.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.

## Claims

1. An ESD (electrostatic discharge) detection circuit, coupled between a first node and a second node, the ESD detection circuit comprising:
a triggering circuit, for generating an ESD trigger signal when the ESD detection circuit is in an ESD mode;
a bias circuit, coupled to the triggering circuit, for providing at least a first bias voltage and a second bias voltage to control an operation of the triggering circuit;
a trigger controlling circuit, coupled to the bias circuit and the triggering circuit, for decreasing a voltage difference between the first bias voltage and the second bias voltage to control a duration of the ESD trigger signal generated by the triggering circuit when the ESD detection circuit is in the ESD mode; and
an activating control circuit, coupled to the trigger controlling circuit and the triggering circuit, for activating the trigger controlling circuit and the triggering circuit to enter the ESD mode according to a voltage level at the first node.

2. The ESD detection circuit of claim 1, wherein the bias circuit is coupled between the first node and the second node; and the bias circuit comprises:
a plurality of diode-connected field-effect transistors (FETs), for generating a plurality of voltage dividing signals as the first bias voltage and the second bias voltage according to voltage levels at the first node and the second node;
wherein not all base terminals of the diode-connected FETs are coupled to source terminals of the diode-connected FETs respectively.

3. The ESD detection circuit of claim 1, wherein the bias circuit is further utilized for providing a third bias voltage; the activating control circuit comprises a resistor and a capacitor where the resistor is serially connected to the first node and a first terminal of the capacitor; and the trigger controlling circuit comprises:
a first FET having a first terminal coupled to the first node and a control terminal coupled to the first terminal of the capacitor;
a second FET having a first terminal coupled to a second terminal of the first FET and a control terminal coupled to the first bias voltage;
a third FET having a first terminal coupled to the second terminal of the second FET, a control terminal coupled to the second bias voltage, and a second terminal coupled to the second node;
a first switching FET having a first terminal coupled to the first bias voltage and the activating control circuit, a second terminal coupled to the triggering circuit, and a control terminal coupled to the second terminal of the second FET;
a second switching FET having a first terminal coupled to the second bias voltage, a second terminal coupled to the triggering circuit, and a control terminal coupled to the third bias voltage; and
a voltage level controlling circuit, coupled between the first terminal of the first switching FET and the first terminal of the second switching FET, for decreasing the voltage difference between the first bias voltage and the second bias voltage according to a voltage level at the second terminal of the second FET when the ESD detection circuit is in the ESD mode.

4. The ESD detection circuit of claim 3, wherein the voltage level controlling circuit comprises:
a first inverter having a first reference node coupled to the control terminal of the second FET, a second reference node coupled to the control terminal of the third FET, an input node coupled to the second terminal of the second FET; and
a fourth FET having a first terminal coupled to the control terminal of the second FET, a second terminal coupled to the control terminal of the third FET, and a control terminal coupled to an output node of the first inverter.

5. The ESD detection circuit of claim 3, wherein the triggering circuit comprises:
a fifth FET having a first terminal coupled to the first node, a control terminal coupled to the first terminal of the capacitor, and a second terminal coupled to the second terminal of the first switching FET;
a sixth FET having a first terminal coupled to the second terminal of the fifth FET and the second terminal of the first switching FET, a control terminal coupled to the first terminal of the first switching FET, and a second terminal coupled to the second terminal of the second switching FET; and
a second inverter having a first reference node coupled to the second terminal of the sixth FET, a second reference node coupled to the second node, an input node coupled to the first terminal of the second switching FET, and an output node for outputting the ESD trigger signal.

6. The ESD detection circuit of claim 1, wherein the triggering circuit, the bias circuit, the trigger controlling circuit and the activating control circuit are implemented by transistors having gate dielectrics where thickness of the gate dielectrics is substantially identical.

7. A method for generating an ESD trigger signal corresponding to a first node and a second node, comprising:
activating an ESD mode according to a voltage level at the first node;
providing a triggering circuit, and utilizing the triggering circuit to generate the ESD trigger signal in the ESD mode;
providing at least a first bias voltage and a second bias voltage to control an operation of the triggering circuit; and
decreasing a voltage difference between the first bias voltage and the second bias voltage to control a duration of the ESD trigger signal in the ESD mode.