What the reasons that I can get A negative IR Drop ?. Is it acceptable ?

[Usha GM]

What the reasons that I can get A negative IR Drop ?. Is it acceptable ?

 

[artmalik]

well negative IR drop would be mean the circuit has inductive properties... it is usually seen in package and power grid simulations. this package inductance usually causes the power bumps which cause vdd surge in the chip power network. this is not acceptable because it causes a ringing effect on the power network. As the voltage goes more than VDD it will have hold time implications which has to be analyzed. the same thing is applicable to VSS network.

This will not be seen on block level analysis because the inductive effects are negligible. the block level is only dependant on resistance and capacitance...