A Four-Channel TDM Clocked-Analog LDO Using a Shared Compensation Block for Thermo-Optic Tuning

This paper presents a four-channel time-division-multiplexing clocked-analog low-dropout regulator (TDM CLDO) using a novel current Miller compensation with a degenerated resistor (CMDR) block for thermo-optic tuning in silicon photonics. Previous TDM LDOs require a dedicated compensation capacitor for each channel because, during controller switching, one node of the compensation capacitor experiences large voltage variations that hinder multiplexing the capacitor. A novel CMDR block that is disconnected from voltage nodes with large variations is proposed to multiplex the compensation capacitor. Furthermore, Gray-code addressing technique is adopted to reduce the crosstalk between four channels caused by clock timing errors. Implemented in a 65 nm CMOS process, this design has a total chip area of 0.0047 mm2, which is 55% smaller than the conventional solution with four identical LDOs and consumes a quiescent current of
$3.1 \mathrm {\mu }\text{A}$
per channel. Measured results show that the presented four-channel TDM CLDO can simultaneously track four 1 Vpp sinusoidal signals up to 200 kHz. To our knowledge, this is the first time that a compensation capacitor is shared between different LDO channels.