A Four-Channel Gray-Code Addressing TDM Clocked-Analog LDO for Thermo-Optic Tuning in Silicon Photonics

This paper presents a Gray-code addressing time division multiplexing (TDM) clocked-analog low-dropout regulator (CLDO) that shares one controller between four output channels with only one compensation capacitor. We apply the Gray-code addressing strategy to reduce the crosstalk. We also apply the split-output amplifier structure to share the compensation capacitor for further chip area reduction. In addition, we introduce a lightweight local-generated supply to increase the dynamic range. Implemented in 130 nm CMOS process, this design has a total chip area of 0.056 mm2 , which is 67.5% smaller than the conventional solution with four identical LDOs. Post layout simulation results show that the presented four-channel TDM CLDO can simultaneously track four 1 V_pp sinusoidal signals at different frequencies with negligible crosstalk. This TDM CLDO is a promising solution for supplying multiple thermo-optic phase shifters (TOPSs) in silicon photonics