Columbia University

Technology Ventures

Optimal Simulator for Mixed Switched-Capacitor/Digital Networks

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An important class of mixed analog-digital VLSI circuits can be termed mixed switched-capacitor/digital (SC/D) networks. These contain capacitors, sources, switches driven by clocks or by signals, and digital logic. The complexity of these circuits is such that simulation is a must, yet traditional simulation tools for time-invariant networks such as SPICE and its variants are not adequate for accurately computing the sharp waveform transitions generated by switching efficiently. Several methods have been reported for simulating general mixed analog/digital networks, but fail to take full advantage of the algebraic nature of network equations in the case of mixed SC/D networks.

Unified Linear Switched-Capacitor Network and Switched-Capacitor/Digital Network Simulator

SWITCAP is a unified linear switched-capacitor network (SCN) and SC/D network simulator. It incorporates comparators, switches controlled by periodic or non-periodic logic signals, and logic gates with multiple inputs in additional to all SCNs regular network elements. The comparators and switches allow for signal dependent modification of circuit topology, and many interesting nonlinear circuits can be modeled. Major features of SWITCAP include: an arbitrary number of switching intervals, many network elements, time-domain analyses of linear SCN’s and mixed SC/D networks, various waveforms for time-domain analyses, frequency domain analyses, and built-in sampling functions.

Lab Director:

Yannis Tsividis, Ph.D.


  • Mixed analog-digital chip design SCN and SC/D circuits are included in charge-redistribution A/D and D/A converters, PCM codecs, switched-capacitor VCOs, rectifiers, and phase-locked loops.


  • Unified SCN and SC/D simulator
  • Efficient and accurate simulation
  • Time and Frequency domain analyses

Tech Ventures Reference: IR Proxy30

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