A CMOS micro-power wideband data/power transfer system for biomedical implants

This paper presents a low power wideband data/power transfer system for fully implantable medical devices such as a cochlea implants. Generally, low-power data/power transfer systems have two modes of operation; Power transfer and data transfer. Unlike recently reported low-power data/power transfer schemes in which data is transmitted separately from power [1], in this implementation, power and data are transmitted together via an inductive link. Using on/off keying with PWM Modulation enables continuous power transfer irrespective of the data being transmitted. Also the clock is extracted from the PWM envelope, making an on-chip clock generation circuit unnecessary. Measured results on a test chip show worst case PWM data discrimination of 10%, making a tighter encoding scheme possible. The proposed system is tuneable via a single bias current from 1 kHz to 2 MHz modulation frequency making it suitable for a wide range of low power unidirectional communication systems. The experimental Power Supply immunity was as large as ±15% for V_DD=4 V. Although the fabricated chip was not optimised for low power, it only consumed 16 μW for a bias current of 160 nA@50 kHz on a standard CMOS process. A more recent optimised version of the chip consumes only about 3 μW of power.