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HSPICE measure absolute value

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Albertll

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Hi, I want to measure the delay of my comparator.

The delay is defined from the rising moment of Clkc to comparator's output differential voltage(Outp-Outn) reaching 0.8v.

Because Outp may be bigger or smaller than Outn, I want to measure the absolute value of (Outp-Outn)

So I enter the code:
.param abs_vout= 'abs(v(Outp)-v(Outn))'
.measure tran delay when 'v(abs_vout)' ='0.8' from='t1' rise=1 (t1 us the rising moment of Clkc)

And there has a waring:Unable to find reference node abs_vout

If I enter:
.measure tran delay when 'v(abs(Outp-Outn))' ='0.8' from='t1' rise=1
Then there has a syntax error

How should I modify my HSPICE code ? Thanks very much !!!
 

Albertll said:
So I enter the code:
.param abs_vout= 'abs(v(Outp)-v(Outn))'
.measure tran delay when 'v(abs_vout)' ='0.8' from='t1' rise=1 (t1 us the rising moment of Clkc)
Click to expand...
And there has a waring:Unable to find reference node abs_vout
Click to expand...
I think HSPICE here expects a node voltage, not a parameter.

Albertll said:
If I enter:
.measure tran delay when 'v(abs(Outp-Outn))' ='0.8' from='t1' rise=1
Click to expand...
Then there has a syntax error
Click to expand...
Did you try:
.measure tran delay when 'v(abs(V(Outp)-V(Outn)))' ='0.8' from='t1' rise=1
Click to expand...
?

You could also try:
.MEASURE TRAN delay TRIG AT=’t1’ TARG V=’abs(V(Outp)-V(Outn))' VAL=0.8 [RISE=1]
Click to expand...
 

.param declares and assigns a value to a variable.

v(outp) is a vector.

You are trying to then .measure abs_vout (a variable)
when .measure operates on vectors (by name).

I think what you want is two .measure statements to
find the delays separately of v(outp) and v(outn), and
then do the .param abs() math on those two delay values.
 

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