sharing nwell of of device and guarding

[deepak242003]

n-well shielding

hello all,

Is there any issue if we share nwell of PMOS wiht that of guardring ?..??

or is it better to maintaing minimum well spacing between them.??

all kind of view are welcome...

deepak

 

[erikl]

Is there any issue if we share nwell of PMOS with that of guardring ?..?? or is it better to maintain minimum well spacing between them.??

Sharing an n-guardring with the nwell practically is (nearly) the same as putting nwell-taps with minimum spacing at the periphery of the nwell, which is a smart practice anyway and very much recommended for good shielding. If you want even better shielding, put a p-guardring around the nwell with (at least) minimum spacing.
An extra (minimum spacing) n-guardring around the nwell doesn't make sense, in contrary could be detrimental as to build another parasitic npn BJT with the nwell.

 

[deepak242003]

thanks for a convincing explanation



cheers