Electrostatic discharge (ESD) protection circuit including an avalanche semiconductor controlled rectifier (SCR) with parallel connected static trigger control circuit (TCC)
A two terminal semiconductor controlled rectifier (SCR) device has an anode terminal coupled to a first node and a cathode terminal coupled to a second node. Neither of the cathode gate or anode gate of the SCR device are connected to a triggering circuit for controlling turn on of the SCR device. The SCR device has an avalanche breakdown voltage for turn on, where that avalanche breakdown voltage is set by a breakdown avalanche of a PN junction of the SCR device. A circuit path includes a series connected chain of M Zener diodes with a blocking diode that are coupled between the first node and the second node. The circuit path has an activation voltage for turn on, where that activation voltage is dependent on N times a Zener diode reverse breakdown voltage. The activation voltage is less than the avalanche breakdown voltage.
1 . An electrostatic discharge (ESD) protection circuit, comprising:
a first semiconductor controlled rectifier (SCR) device of two terminal, self-turn on, type consisting of an anode terminal and a cathode terminal, and wherein said first SCR device has an avalanche breakdown voltage for self-turn on;
wherein said avalanche breakdown voltage is set by a breakdown avalanche of a PN junction of the first SCR device;
wherein the first SCR device includes an NPN-type bipolar transistor coupled to a PNP-type bipolar transistor, and wherein said PN junction of the first SCR device is a junction between a collector and base of the NPN-type bipolar transistor;
a first circuit path having a first node and a second node, and wherein said first circuit path has an activation voltage for turn on;
wherein the first SCR device and first circuit path are connected in parallel with the anode terminal and the first node coupled to a first pin and with the cathode terminal and the second node coupled to a second pin;
wherein said activation voltage is less than the avalanche breakdown voltage;
wherein the first circuit path comprises a series connected chain of M Zener diodes that are coupled between the anode terminal and the cathode terminal of the first SCR device, with each Zener diode has a size N greater than or equal to 20, where N is a number of diode structures connected in parallel for each Zener diode.
2 . The ESD protection circuit of claim 1 , wherein both a cathode gate node and an anode gate node of the first SCR device are not connected to a triggering circuit for controlling turn on of the first SCR device.
3 . The ESD protection circuit of claim 1 , wherein said activation voltage of the first circuit path is dependent on M times a reverse breakdown voltage of the Zener diode.
4 . The ESD protection circuit of claim 3 , wherein said first circuit path further includes a diode directly connected in series with the series connected chain of M Zener diodes.
5 . The ESD protection circuit of claim 4 , wherein a cathode of the diode faces the cathode of the Zener diode in said series connected chain of M Zener diodes to which said diode is directly connected.
6 . The ESD protection circuit of claim 1 , further comprising a second SCR device of two terminal type consisting of an anode terminal and a cathode terminal, and wherein the anode terminal of the second SCR device is coupled to the anode terminal of the first SCR device, and wherein the cathode terminal of the second SCR device is coupled to the first pin.
7 . The ESD protection circuit of claim 6 , wherein the first pin is a signal pin for input/output of an integrated circuit and the second pin is a reference pin for a ground reference of the integrated circuit.
8 . The ESD protection circuit of claim 6 , wherein the first pin is a reference pin for a ground reference of an integrated circuit signal and the second pin is a signal pin for input/output of the integrated circuit.
9 . The ESD protection circuit of claim 6 , wherein said second SCR device has an avalanche breakdown voltage for self-turn on.
10 . The ESD protection circuit of claim 9 , wherein both a cathode gate node and an anode gate node of the second SCR device are not connected to a triggering circuit for controlling turn on of the second SCR device.
11 . The ESD protection circuit of claim 9 , further comprising:
a second circuit path having a first node and a second node, and wherein said second circuit path has an activation voltage for turn on;
wherein the second SCR device and second circuit path are connected in parallel; and
wherein said activation voltage of the second circuit path is less than the avalanche breakdown voltage of the second SCR device.
12 . D) The ESD protection circuit of claim 11 , wherein:
said activation voltage of the first circuit path is dependent on M times a reverse breakdown voltage of the first Zener diode; and
the second circuit path comprises a series connected chain of Mb second Zener diodes that are coupled between the anode terminal and the cathode terminal of the second SCR device, wherein said activation voltage of the second circuit path is dependent on Mb times a reverse breakdown voltage of the second Zener diode.
13 . The ESD protection circuit of claim 12 , wherein the number M of first Zener diodes in the first circuit path and the number Mb of second Zener diodes in the second circuit path are equal.
14 . The ESD protection circuit of claim 12 , wherein the number M of first Zener diodes in the first circuit path and the number Mb of second Zener diodes in the second circuit path are not equal.
15 . The ESD protection circuit of claim 12 , wherein said second circuit path further includes a diode directly connected in series with the series connected chain of Mb second Zener diodes.