Abstract: An ESD structure, including a first conductive type substrate, a second conductive type well region in the substrate, first/second doped regions (the first type), fourth to sixth doped regions (second conductive type), and first/second gates, is provided. The first/second doped regions are respectively disposed in the well region and the substrate. The first/second gates are on the substrate surface with no well region below. A third doped region is between the first and second gates in the substrate. The fourth doped region is in the substrate and on one side of the first/second gates. The fifth doped region is in the substrate, extends into the well region, and on another side of the first/second gates. The first doped region is located between the fifth and sixth doped region. The first/sixth doped regions and the first gate are connected. The fourth/second doped region and the second gate are connected.

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.

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.

Abstract: An electrostatic discharge (ESD) protection circuit connecting to an input pad is configured to dissipate an ESD current. The circuit has a substrate of a first conductivity type, a first well of a second conductivity type in the substrate, and a second well of the first conductivity type in the first well. The circuit further has a diode device having a first end of the first conductivity type electrically coupled to the input pad and a second end of the second conductivity type in the second well. Moreover, the protection circuit has a first doped region of the second conductivity type in the first well electrically connecting to the input pad, and a second doped region of the first conductivity type in the substrate electrically coupled to the ground. The circuit also has a channel formed between the input pad and the second doped region to provide an ESD current discharge.