If there's no setup margin, how to fix hold?

o   If setup and hold both are critical on same path, check if it is exact same path or if there is any diversion from combo logic in setup and hold timing path.

o   If there is any diversion, add delay at that point so hold can be fixed without touching setup critical path.

o   If timing path is exactly same and having setup and hold violations, there could be two reasons,

o   Crosstalk impact – crosstalk will add delay in setup and reduce it in hold. Impacting adversely both setup and hold. Fixing crosstalk should give margin to fix setup and hold.

o   If there is no crosstalk, there can be very high setup and hold time requirement from endpoint. (may happen with reg2mem paths)

§  Check if such cells can be replaced with less access time cell.

§  To get margin in setup and hold both, you need to use cell with less delay variation across SS-FF corners.

§  Use LVT cells in data path instead of SVT/HVT. Use low drive strength cells and reduce net legth so that OCV impact can be reduced giving margin for setup and hold.