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A high-rate frequency shift keying (FSK) data transfer protocol and demodulator circuit has been developed with a data-rate to carrier-frequency ratio up to 67%. Its primary application is in the wireless biomedical implants in need of data transfer rates above 1 Mbps. The demodulator circuit extracts the serial data bit stream and a constant-frequency clock from an FSK carrier signal in the 2∼20 MHz range, which is used to power the implant through inductive coupling. The chip occupies 0.41 mm2 in the AMI 1.5 μm 2M/2P standard CMOS process and has a simulated data-rate of up to 2 Mbps and a measured rate of 200 Kbps while consuming less than 0.5 mW.