A linear voltage regulator for an implantable device monitoring system

This paper describes a CMOS implementation of a Linear Voltage Regulator (LVR) used to power an implanted physiological signal system that is used to monitor the blood pressure. The topology is based on a classical structure of a Low Dropout Regulator (LDO) and receives his activation energy from a RF link characterizing a passive RFID tag. The LVR was designed to achieve important features like low power consumption, and a small silicon area without the need for any external discrete components. The low power operation represents an essential condition to avoid a high energy RF link, thus minimizing the power of the transmitter and the thermal effects on the patient tissues. The project was diffused in a 0.35 mu m CMOS TSMC technology and a prototype was tested to validate the overall performance. The LVR output is regulated at 1 V and supplies a maximum load current of 0.5 mA @ 37 degrees C. The load regulation is 13 mV/mA and the line regulation is 39 mV/V. The LVR total power consumption is 1.2 mW.