symmetric and asymmetric LDMOS

[prcken]

what's the reason to use asymmetric type instead of symmetric one for LDMOS ESD device?
only for save layout area?

 

[dick_freebird]

If you don't need the pin to swing below ground or can
stand to forward bias the body when it does, you could
use asymmetric and have more functional density (better
ESD for area, or less area for equal clamping quality).