At present I'm trying to implement a DC-DC converter control system-type circuit in CMOS. As part of this, I'm trying to work through some mathematics and create transfer functions of the circuit.

Part of the circuit is implemented in discrete-time, switched capacitor circuits; however, it is necessary for various reasons to have passive components forming poles and zeroes at various nodes at low enough frequency to effect the behavior of the discrete time components. How would I model this, as I would assume the SC circuit requires z-domain and the passive filters require s-domain??

Thanks for your help!