ESD - SCR, npn, PN diode type question

There are some kinds of ESD devices.
In my PDK, there are SCR-type ESD-diode, NPN-type(diode connected) ESD-diode, P+/NW diode.
what's the difference of these three ESD??

So what kind of type can I use with various circuit??

Thanks in advance.
Regards.

Very wide field to aswer on all questions in one post. Try to read something there are a lot of books on EDABoard.

All ESD protection elements can be divided by 2 category:
1) Breakdown: e.g. TFO (thick field oxide), GGNMOS (gate grounded NMOS), GCNMOS (gate coupled NMOS), LV/MV/HV SCR (low/mwdium/high voltage silicon controlled rectifier) etc.
2) Non-breakdown: e.g. diodes in forward direction, RC-timed clamps etc.

All of them are differentiate by breakdown voltage, snapback voltage (Vt1) etc.

The first of all don't use diode in reverse direction as protection element. It always has low current capability.

NPN device (snapback action) is often used. It has moderate current capability per area unit. TFO, GGNMOS and GCNMOS also can be called as NPN device.

SCR device (also snapback action) is very sensitive to process, can be triggered by rapid change of voltage, usually HV. But it has the best current capabily per area unit. If u don't sure in this device it's better don't use it.

Recommend you a book related this subject
Nano-CMOS Circuit and Physical Design Wiley 2005
It is available in this forum.

DenisMark said:

The first of all don't use diode in reverse direction as protection element. It always has low current capability.

Click to expand...

I think, that this statement is too categorical. Majority DAC and ADC known firms have pure diode ESD protection (except for clamp circuits on a supply/bias/reference pads).
It seems to me, that at a choice of the circuit of protection it is necessary to start with the requirements incorporated in the specification to parameters of input/output signals and requirements to a level of ESD protection.

There are lots of books describe the three kinds,just as the Art of Layout