A Jitter Reduction Circuit Using Autocorrelation for Phase-Locked Loops and Serializer-Deserializer (SERDES) Circuits

A new jitter reduction circuit is proposed for reducing the timing jitter in a serializer-deserializer (SERDES). Instead of using elaborate hardware to calculate the jitter, we use the jittered signal´s autocorrelation to remove the jitter. The motivation for this work was to provide a reduced jitter phase-locked loop (PLL), so that incorporating a built-in self-testing (BIST) mechanism for PLL´s and SERDES would be simplified. The technique involves transmit and receive side jitter reducer pulse shaping circuits made of only 14 and 20 transistors, respectively. They reduce the jitter in the clock generated by the PLL at the transmit side, and the jitter between the recovered clock and the serial data at the receive side. The jitter reducers are designed in 70 nm Berkeley Predictive process models and tested with various types of input jitter. In the case of the transmit side, the peak-to-peak random jitter (RJ) is reduced, on average, by 45.51% and also the average transmit and receive side RMS jitter is reduced, on average, by 62.24% and 35.88%, respectively. The bit-error rate (BER) of the SERDES computed probabilistically is improved from 8.3 times 10^-2 to 6.44 times 10^-20, for input RMS periodic jitter (PJ) of 71.77 ps. The BER for the PCI express bus must be les 1 times 10^-12.