Dear Group Members,
I have been attempting to use the following commands to calculate the output rise and fall times of an inverter and the propagation delay with the following voltage source:
PULSE(0 3.3 1n 1.5n 1.5n 5n 10n)
.MEAS TRAN fall_delay
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
.MEAS TRAN rise_delay
+ TRIG V(Vout) VAL=3.3*0.1 TD=0NS RISE=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0NS RISE=1
.MEAS TRAN propagation_fall
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 RISE=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 FALL=1
.MEAS TRAN propagation_rise
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 RISE=1
Unfortunately the results from the .MEAS text do not agree with manual plotting and reading of the waveforms.
i.e.
From Waveform, Rise time = 118ps, Fall time = 152ps
From text, Rise time = 6.7ns, Fall time = 1.6ns
Clearly, I am doing something fundamentally wrong with the .MEAS command but I have been unable to resolve this further. I would really appreciatte some feedback and can supply the circuit schematic and inverter model if required.
Many thank, Ken Potter.
