On-chip coils with integrated cores for remote inductive powering of integrated microsystems

This paper reports on integrated receiver coils and accompanying circuitry for wireless powering of integrated microsystems, emphasizing implantable biomedical applications. These planar spiral coils consist of an electroplated Cu winding and electroplated NiFe core, and they can be post processed directly on top of integrated circuitry. Ten turn, 20 mm² versions of these coils operating at 4 MHz have a Q of 6.6, and can supply loads of a few kΩ with over 15 mW of DC power transmitted a distance of 3 cm. A receiver chip optimized to work with these coils has been fabricated and tested. Together with a coil, this circuit can supply over 3 mA DC at 4 V to an integrated microsystem. It also demodulates 50 kbps of ASK encoded data, and generates a 1 MHz system clock