powerclamp is used between vdd and vss, it provide a path for esd discharge, for mutliple power chip, there must be a power rail to rail for providing the esd discharge path.
normal , powerclamp circuit can be diode or ggnmos and rail to rail(someone call powercut )circuit can use at least two diode (anti parrallel).
P mos device can also be used as clamp based on the fact that if the gate drive is 0, it is default as on, so it can serve as a path from VDD to ground, but of course a lot of supporting circuit are required to make sure it does not impact normal circuit function.
P mos device can also be used as clamp based on the fact that if the gate drive is 0, it is default as on, so it can serve as a path from VDD to ground, but of course a lot of supporting circuit are required to make sure it does not impact normal circuit function.
The following book has a section in chapter 4 about power clamps. You can download it here via the link. Hope that this helps you for the better understanding of power clamps.
On-Chip ESD Protection for IC - An IC Design Perspective, Albert Z. H. Wang
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Power clamp is used for ESD protection.
There are 2 blocks, one is ESD detection block and other one is big mos transistor between power and ground and it's gate should be connected to ESD detection block.
The idea of ESD detection block is that ESD surge is faster rising time than normal power up time.