A digitally controlled adaptive LDO for power management unit in sensor node

Abstract

Power management unit (PMU) is the core of the sensor node SoC to achieve high performance in wireless body area network (WBAN). This article presents a low power digitally controlled low dropout regulator (LDO) targeted for the power management unit (PMU) in a sensor node. A flash-based approach, substituting the classical error amplifier with an array of dynamic comparators, is employed in order to achieve fast transient response. The proposed LDO minimizes dynamic power consumption by employing clock gating to the comparator array through detecting any abrupt change in load demand with a modular topology. In addition, during the load transient, the proposed LDO effectively detects the voltage droop and generates a set of digital control signals to activate a specific PMOS array for coarse tuning (CT) and fine-tuning (FT). The proposed LDO is capable of handling a load step of 10 μA to 1 mA with a voltage droop of 287 mV. The LDO is implemented with 180 nm CMOS technology node, producing a regulated output voltage of 0.9 V for input voltage ranges from 0.8 V to 1.8 V. The current efficiency at 1 mA load current is 99.4%, with settling time to recover the voltage droop is 80 ns at 50 MHz clock frequency.