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ASIC

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Hi,

I have a chip design that can only be driven by AC power. I can do a diode bridge on the die, but how do I connect the substrate? Anyone has any experience with this?


ASIC
 

napong

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Hi,

Usually I connect the substrate to the VDD after rectification. But the substrate junction which normally reversed will be forworded at each peak of AC input. So try to make AC peak to VDD drop as small as possible to make small forwarded substrate junction and check your substrate current will not exceed limit.

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ASIC

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Thanks napong for your reply. Could you explain further:

What is the process you use? BiCMOS? P+ Substrate right?

Why do you connect VDD to the substrate and not GND? Normally the substrate is connected to the lowest potential to prevent the substrate junction from conducting.

What happenes to the remaining circuit when the substrate junction conducts on the negative half-period of the cycle?

Any software available to simulate this scenario?

Some (known working) example layout would be useful if you have it?

ASIC
 

napong

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I use CMOS process. But I made a diode from PMOS with drain-gate connected so my diode is in a Nwell and I connected Nwell to VDD.
For substrate, I also connected to GND.

Sorry for my wrong information.
napong.
 

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