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blowup limit exceeded error during ADC simulation

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npsnpsnps

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Hello,

I am designing a Switched Capacitor DAC in SAR ADC. I have used ideal switches in my DAC design. I simulated the DAC and got the correct output but when i integrated with other blocks to create the ADC and simulated, I am getting the below error. I have used the ideal comparator in my ADC.

Error

ERROR (SPECTRE-16384): Signal I(I8.I51:vout_flow) = -1.29358 GA exceeds the blowup limit for the quantity `I' which is (1 GA). It is likely that the circuit is unstable. If you really want signals this large, set the `blowup' parameter of this quantity to a larger value.

Analysis `tran' was terminated prematurely due to an error.


I8 is my DAC block and I51 is the Ideal switch used in DAC.
 

Looks like the GA current is brought up by the way you designed your circuit. Fortunately there are no ideal switches in a real IC...

May be you shorted circuit nodes inadvertently.
 

Zero ohm source, zero ohm switch, zero ohm capacitor,
what could possibly be the problem?

Switch models are problematic especially when you
make them ideal - divide by zero and so on. Either make
the on resistance (and off resistance) properties finite,
or add explicit series and shunt resistances.

It is also good to make the switch actuation something
other than hyper-abrupt, so that derivatives are not
insane-by-definition.
 

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