[SOLVED] boost pmos nwell body switch layout design

[analogicrd]

i am doing a body switch circuit for boost power pmos nwell voltage level selection switching.
but when boost system enter DCM operation, the power pmos nmos switching node (SW/LX) voltage will higher than the nwell voltage,
so the current follow from SW to nwell,
the average current will be up to 10mA, and the peak is up to 200mA,
anybody does this before?

thanks

 

[dick_freebird]

You will need to float the NWell and probably use a
diode pair, to make NWell (and associated gate drive)
follow the higher of VIN or SW. Now this adds a foot-
race between diode Vf and PMOS VT to the mix. You
might look into synchronous rectifier schemes. Body-
blocked PMOS switches have been a common thing
in analog MUXes. But those days also had VT > Vf.

 

[analogicrd]

ok, thanks a lot.