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  1. #1
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    Zero diagonal found in Jacobian error in simulation the DAC?

    I face with the problem Zero diagonal found in Jacobian when I run the simulation for DAC with bridge capacitor architechture. The error happens when I use MIM capacitor in the PDK. However, the simulation is run succesfully when I use ideal capacitor. How can I deal with this issue? I use IC 5141 simulator.
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  2. #2
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    Re: Zero diagonal found in Jacobian error in simulation the DAC?

    check the quality of the MIMs capacitor model in a simple circuit, like an RC low pass filter.
    then try a more complex circuit -say throw in an op amp and a second MIM capacitor, say a SallenKey filter.

    reduce the number of capacitors - try just the LSB or MSB.



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  3. #3
    Advanced Member level 5
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    Re: Zero diagonal found in Jacobian error in simulation the DAC?

    Zero diagonal IME is from floating nodes (infinite resistance
    transforms to zero conductance). This can be from "buried"
    connectivity that hides at the bottom level of subcircuits
    or even in compact-model instances that leave "code stubs"
    if you fail to provide params that would enable "closure".

    Be sure you have filled any instance properties that express
    connectivity such as well and substrate net connections.



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