ESD protection circuit with active triggering
An ESD protection circuit is provided. The circuit includes a discharging component, a diode, and an ESD detection circuit. The discharging component is coupled between an input/output pad and a first power line of an IC. The diode is coupled between the input/output pad and a second power line of the IC in a forward direction toward the second power line. The ESD detection circuit includes a capacitor, a resistor, and a triggering component. The capacitor and the resistor are formed in series and coupled between the first power line and the second power line. The triggering component has a positive power end coupled to the input/output pad and a negative power end coupled to the first power line. An input of the triggering component is coupled to a node between the capacitor and the resistor.
1. An electrostatic discharge (ESD) protection circuit, comprising:
a first discharging component, coupled between an input/output pad and a first power line of an IC;
a second discharging component, coupled between the input/output pad and a second power line of the IC;
a first diode coupled between the input/output pad and a first ESD bus in a forward direction toward the first ESD bus; a second diode coupled between the first ESD bus and the second power line in a forward direction toward the first ESD bus;
a third diode coupled between the input/output pad and a second ESD bus in a forward direction toward the input/output pad;
a fourth diode coupled between the second ESD bus and the first power line in a forward direction toward the first power line; and
an ESD detection circuit, comprising:
a capacitor and a resistor formed in series, and coupled between the first power line and the second power line;
a first triggering component, having a first positive power end coupled to the first ESD bus and a first negative power end coupled to the first power line; a first input of the first triggering component being coupled to a node between the capacitor and the resistor; and
a second triggering component, having a second positive power end coupled to the second power line and a second negative power end coupled to the second ESD bus, a second input of the second triggering component being coupled to the node between the capacitor and the resistor;
wherein the first and the second discharging components are turned off during normal power operations; the first discharging component is triggered by a first output of the first triggering component in a first ESD event, and the second discharging component is triggered by a second output of the second triggering component in a second ESD event.
2. The ESD protection circuit of claim 1 , wherein the first discharging component is a gate-driven NMOS, a gate-grounded NMOS, an NMOS with its gate terminal coupled to a pre-buffer, an NPN BJT, or a P-type substrate-triggered SCR.
3. The ESD protection circuit of claim 1 , wherein the second discharging component is a gate-driven PMOS, a gate-VDD PMOS, a PMOS with its gate terminal coupled to a pre-buffer, a PNP BJT, or a N-type substrate-triggered SCR.
4. The ESD protection circuit of claim 1 , wherein the first triggering component is an inverter, an M-input NAND with all inputs coupled together, or an N-input NOR with all inputs coupled together, M and N are positive integers larger than 1, respectively.
5. The ESD protection circuit of claim 1 , wherein the second triggering component comprises one selected from the group consisting of: two inverters coupled in series, an M-input NAND coupled in series with an N-input NAND, and an M-input NOR coupled in series with an N-input NOR, an M-input NAND coupled in series with an N-input NOR, wherein the M inputs are coupled with each other, the N inputs are coupled with each other, M and N are positive integers larger than 1, respectively.