ahnsei ,
This is a switched capacitor filter - with a variety of configurations for each mode of operation based on the switching frequency. To create a transistor level SPICE model would be unrealistic (which is probably why you haven't found one), so I would suggest looking at the datasheet and specifically, looking at each mode of operation and seeing if you can approximate the filter topology with an expression for the transfer function given in the datasheet (by calcuting based on the switching frequency).
Based on the expression you get, you can use the Multisim component "TRANSFER_FUNCTION_BLOCK" to plug in the correct transfer function and thus approximate the behavior of the filter in the circuit.
This transfer function can be found in the Master database -> Sources -> CONTROL_FUNCTION_BLOCKS. There was a previous discussion giving some additional details on how to setup the transfer function block:
http://forums.ni.com/ni/board/message?board.id=370&thread.id=3987
Regards,
Patrick Noonan
Business Development Manager
National Instruments - Electronics Workbench Group
50 Market St. 1-A
S. Portland, ME 04106
Email: patrick.noonan@ni.com
Tel. (207) 892-9130
Fax. (207) 892-9508
