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Design >> Mixed-Signal Design >> gmin value for switched cap delta-sigma mod
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Message started by panditabupesh on Feb 21^st, 2007, 4:03pm

Title: gmin value for switched cap delta-sigma mod
Post by panditabupesh on Feb 21^st, 2007, 4:03pm

Hello
I am designing a 4th order switched-capacitor delta-sigma modulator. During mismatch analysis (transient) I observed that the modulator was power-on unstable for the default gmin value (1pS) . Decreasing gmin to 100fS the modulator appears to be stable for the power-on conditions.
Though I have provided a control signal to reset the integrators - however, I would still like to understand the cause and implications of power-on instability for the default gmin value. Also, gmin value appears of consequence only when mismatches are introduced in the modulator- the mismatch free modulator is power-on stable.

Thanks
Bupesh