This post is about characterizing or calculating pin average toggling power for any on chip module, using SPICE simulations, Toggling power or Dynamic power is the power dissipated during the transition of any input signal from low to high or high to low. During this time certain amount of current is drawn from the supply voltage, which again eventually gets settled to its leakage value or static value after the operation is done. The condition being that it should be a relaxed timing operation so that the current is settled.
The power dissipated from the starting of the operation till the current settles down to its final value give the dynamic pin power.
How to calculate
1. All the timing signals should be relaxed so that all the current gets settled after switching of the signal
2. In Fig.2 I(A1) shows the current waveform for the current drawn from the source driving A1.
3. Lkgppt1 and Lkgpt2 are the time point where leakage current should be calculated as here the current is perfectly settled
4. Rise window is the time where average current from the source driving A1 is calculated, this gives the Average Rise Dynamic Current
5. Fall window is the time where average current from the source driving A1 is calculated, this gives the Average Fall Dynamic Current
6. Leakage component of the system is max (Leakage at Lkgpt1 and Leakage at Lkgpt2)
7. Dynamic Rise current = Average Rise Dynamic Current – max (Leakage at Lkgpt1 and Leakage at Lkgpt2)
8. Dynamic Fall current = Average Fall Dynamic Current – max (Leakage at Lkgpt1 and Leakage at Lkgpt2)
9. RISE POWER = Dynamic Rise Current X Supply Voltage
10. FALL POWER = Dynamic Fall Current X Supply Voltage