A Low-Voltage and LDO-Less Wireless Pressure Sensor Readout System With Current Mode Pseudo-PLL and Charge Pump-Powered UWB Data Transmission for Implantable Health Monitoring

This article presents an implantable pressure sensor readout system (IPRO) that can work at low voltage and does not need an internal low dropout regulator (LDO). This article has made a series of optimizations for power consumption. The power supply of IPRO uses 434-MHz energy harvesting (EH), which only uses two-stage rectification and is equipped with a corresponding ultralow power undervoltage locking (UVLO) circuit. The analog front-end (AFE) and signal-processing parts use current mode and differential pseudo-phase-locked loop (DPPLL), which can work stably under low voltage and maintain a certain degree of accuracy and power rejection ability. The wireless data transmission part adopts the impulse ultrawideband (IR-UWB) scheme. Its ultralow power consumption allows it to be powered by a charge pump, which is the first time it has been proposed in implantable systems. To further optimize power consumption, the simplest encoding circuit suitable for the front-end output form was proposed, and a power oscillator (PO) with accelerated start-up was used to optimize area and power consumption. The system is implemented in a 180-nm complementary metal oxide semiconductor (CMOS) process, with a chip area of 1.1 * 1.0 mm2. The measurement results indicate that the typical working voltage of the IPRO is 0.8 V, the typical power consumption is $11.8~\mu $ W, and the accuracy is 1.11 mmHg. Compared with existing designs, there is a significant optimization in supply voltage and power consumption.