US 2014/0197450 A1 · ESD PROTECTION CIRCUIT

Abstract

An electrostatic discharge (ESD) protection circuit is coupled between first and second pads to protect an internal circuit therebetween. Under a normal operating condition, a voltage on the first pad is higher than that on the second pad. The ESD protection circuit includes a substrate of a first conductivity type; first well of a second conductivity type in the substrate, wherein the first well is coupled to the first pad; a snapback device housed in the first well; and a diode string in the substrate, connected in series with the snapback device and separated from the first well, wherein the serially connected diode string and snapback device is connected between the first pad and the second pad. With the isolation from the first well, the holding voltage of the ESD protection circuit can be tuned by adjusting the number of diodes in the diode string without using a guard ring.

Claims22

Dependent claims

An electrostatic discharge (ESD) protection circuit coupled between a first pad and a second pad, a voltage on the first pad being higher than a voltage on the second pad under a normal operating condition, wherein the ESD protection circuit comprises:

a substrate of a first conductivity type;
a first well of a second conductivity type in the substrate, wherein the first well is coupled to the first pad;
a snapback device housed in the first well;
and
a diode string in the substrate, connected in series with the snapback device and separated from the first well, wherein the first well is coupled to the first pad or a cathode of the diode string.

2 more elements

a substrate of a first conductivity type;
a first well of a second conductivity type in the substrate and coupled to the first pad;
a device well of the first conductivity type in the first well and coupled to the second pad;
a first doped region of the second conductivity type in the device well;
a second doped region of the second conductivity type in the device well and coupled to the second pad;
a first gate between the first and second doped regions and over the device well and coupled to the second pad;
and
at least one diode region, wherein each diode region comprises:
a diode well within the substrate;
a third doped region of the first conductivity type in the diode well;
and
a fourth doped region of the second conductivity type in the diode well, wherein the at least one diode region is connected in series with the first doped region and couples the first doped region to the first pad,
wherein the first well is coupled to the first pad by directly coupling to the first pad or by coupling to a fourth doped region of any diode region.

10 more elements

a substrate of a first conductivity type;
a first well of a second conductivity type in the substrate and coupled to the first pad;
a first device well of the first conductivity type in the first well and coupled to the second pad;
a second device well of the second conductivity type in the first device well and coupled to the first pad;
a first doped region of the first conductivity type in the second device well and coupled to the first pad;
a second doped region of the second conductivity type in the first device well;
at least one diode region, wherein each diode region comprises:
a diode well within the substrate;
a third doped region of the first conductivity type in the diode well;
a fourth doped region of the second conductivity type in the diode well, wherein the at least one diode region is connected in series with the second doped region and couples the second doped region to the second pad, and
a second well of the second conductivity type in the substrate, wherein the second well is coupled to the first pad by directly coupling to the first pad or by coupling to the second doped region.

8 more elements

Dependencies are inferred from the claim text.

Esd protection circuit

Life of this patent

Esd protection circuit

Life of this patent

Abstract

Claims22