How to use spectre calculator to return x value of a given y? Thanks.

Given that crossMethod is the internal function called within the cross function, and it is passed the same arguments as cross, it appears that the first argument to cross has been given as a scalar value rather than a waveform, so it's not surprising that it doesn't work. 

Regards,

Andrew 

Hi,

This is my calculator expresion:

cross(IDC("/I0/icv0") 24e-6 1 "either" nil nil  )

Regards, 

Hi,

Isn't IDC() going to return a single scalar value rather than a waveform (as Andrew pointed out being the source of the problem for the cross function) ?  In other words, wouldn't the DC current be static, and therefore not cross any thresholds?

Hope this helps,

Lawrence.

The IDC function returns a current from the dc operating point. So it is a single value - there's no variation and hence it makes no sense to use cross on it. Put another way, it will resolve to a number - there's no x axis, and only a single y value. 

Andrew 

 Hi Francisco,

I think Andrew's comment may be correct. Will not the function "IDC("/I0/icv0") return a scalar value? If you are trying to find a value from a DC analysis, perhaps you can use the value() function to interpolate between two values.

Shawn

If it's a dc sweep, then you should use IS() rather than IDC(), and you can find the x value for a given y with cross, or the y value for a given x using value().

Andrew 

Thanks to all of you, the right function for my mesaurement is IS rather than IDC.

 Best regards 

Hi  I want the x-axis value of a waveform for a given y value.

My measurement statement throws error saying "Expression evaluates to nil". Need your expert help in understanding where am going wrong.

Measurement statement is : 

cross(clip(dB20(VF("/vout")) 10 1G ) ymax(clip(dB20(VF("/vout")) 10 1G )) 1 "rising" nil nil )

Basically I am trying to get the X-axis(frequency value) of the clipped output waveform where the wave has the maximum value. The "ymax" expression gives me a correct number.

My virtuoso version is IC6.1.6.500.7

There's a CCR to fix this in an IC617 ISR (it may have been fixed now) which is to allow cross to return a value that it doesn't actually cross but exactly reaches. However, as I pointed out in that CCR, there's a much cleaner solution that already works (forever) and is simpler. Use xmax instead of ymax. That already gives you the x-value where the maximum occurs:

xmax(clip(dB20(VF("/vout")) 10 1G ))

Regards,

Andrew.