Clock Skew Analysis via Vector Fitting in Frequency Domain

An efcient frequency-based clock analysis method: CSAV is proposed in this paper. It computes the circuit response by rst solving the state equation in frequency domain, and derive the ra-tional approximate with the help of vector tting [9]. There are two aspects that contribute to the time efciency of the method. One is CSAV solves the state equation only on selected frequency points, which signicantly reduce the amount of time for equation solving. The other is CSAV performs vector tting and waveform recovery only on user specied nodes, which save the unnecessary computa-tion on the nodes which are not concerned by user. The complex-ity of our method is O(dlg fmaxeN ® + dlg fmaxe2NaNout), where fmax is proportional to the knee frequency of input signal, N is the node number of the circuit, ® is a constant around 1.3, Na is the order of approximation and Nout is the number of output nodes. Our experimental results show that compared with Hspice, CSAV achieves speed-up up to 35 times while the error is only 1%. More-over, computational saving of CSAV grows with circuit size, which makes this method especially promising for large cases. 1