Bi-directional AC coupled interface with adaptive spread spectrum clock generator

We propose a method of reducing a quantization noise and a spectrum peak utilizing an adaptive spread spectrum clocking PLL (SSC-PLL) circuit for bi-directional and AC coupled interface. To realize a high speed, wide range, bi-directional and long cable transceiver, we designed a test chip that contained an Equalizer, CDR, and differential transceiver for long cable, and also an SSC-PLL for reducing spectrum peak with jitter optimization by adaptive bandwidth setting. Utilize this interface, it can be realized up to 810 Mbps and 20-m bi-directional transceiver system with high ESD protection, and spectrum peak reduction about -23 dB effectively with an optimum bandwidth.