How to extract the output impedance R_out of the NMOS and PMOS from IBIS model?
For the R_on of NMOS: in the IBIS model, find the [pulldown] data in the model_type output or model_type 3-state, calculate the R_out by using the [pulldown] voltage data at 0.5V, but also at Vdd 0.5V, both divided by their current data I(typ), then, averaging the R_out at 0.5V and at Vdd-0.5V for the final R_out. For example, for the R_out of PI6C2510-133EL, download the IBIS model 6c2510el.ibs from Pericom’s website, using the data in model_type output (Model 2510E_OUT1), the R_out at 0.5V and at 2.8V (Vdd-0.5V = 2.8V) is: At 0.5V: 0.49841V / 0.0211535A = 23.56-ohm. At 2.8V: 2.79932V / 0.0855804A = 32.71-ohm. The average output impedance R-on for the NMOS is: (23.56-ohm + 32.71-ohm)/2 = 28.13-ohm. The calculation of the PMOS is the same with the NMOS, but using the [pullup] data in the same model of a model_type output. . At 0.5V: |0.498471V / -0.0208299A| = 23.93-ohm. At 2.8V: | 2.79934V / -0.0901073A| = 31.06-ohm. The average output impedance R_on for PMOS is (23.93-ohm + 31.06-ohm
