A Fully-Integrated 27.12 MHz Inductive Power and Data Telemetry Link for Biomedical Implants

Abstract

We present an integrated power telemetry system to simultaneously transmit power and bidirectionally (half-duplex) communicate data over only a single pair of inductive coils. In particular, the system implements a full-wave active rectifier operating at 27.12 MHz with tunable switched-offset biasing for delay compensation. For an input AC voltage of 3 to 5 V and load resistors of 200 Ω to 2 kΩ, the simulated peak voltage conversion ratio and power conversion efficiency reach 93.9% and 85.7%, respectively. A regulated stage-configurable switched-capacitor (SC) DC-DC converter is then introduced to provide harmonic conversion ratios ranging from 1/2 to 1/5, thus reducing conduction loss. The proposed converter achieves > 60% simulated efficiency over a wide range of load current from 50 μA to 5 mA, while delivering load voltages from 6 V to 21 V. Binary phase shift keying (BPSK) modulated on the power waveform is proposed for downlink (at 1 Mbps), while multilevel load shift keying (LSK) is used for uplink (at 0.4 Mbps) to trade off between power transfer efficiency (PTE) and spectral efficiency. A topology-configurable clock and data recovery (CDR) circuit with simulated jitter of 0.021 UI is proposed for fast settling and wide capture range. The proposed telemetry IC system achieves uninterrupted power delivery during half-duplex data communication.