IC BASED RF POWERED IMPLANTABLE
TELEMETRY MICROSYSTEM FOR EMG RECORDING

J. Parramon¹, P. Doguet², M. Verleyssen², L. Leija³, J. Arzuaga⁴, E. Valderrama^1
1CNM parramon@cnm.es, elena@cnm.es
²UCL doguet@dice.ucl.be, verleyssen@dice.ucl.be
³CINVESTAV lleija@mvax1.red.cinvestav.mx
⁴CCC ccc@netgate.comintur.com.uy

INTRODUCTION This paper presents the development of an implantable telemetric microsystem for recording purposes focusing on the system concept, mixed-mode IC design and packaging. In conjunction with another paper where inductive link design is explored carefully, a new wireless high bit-rate transcutaneous telemetry system is presented including a small size IC-based implant with telemetric and EMG recording circuitry.

METHODS IC development for implantable microsystems offers a wide range of advantages, like size reduction, high design flexibility and power economy. A 2 microns BiCMOS 5.0 x 5.2 mm² mixed-mode integrated circuit containing not only the telemetric part (5V regulator, receiver, transmitter, decoder, coder, etc.) but also the application specific part in that case for recording purposes (amplifiers, filters, time multiplexer and A/D converter) is in fabrication. Design guidelines fitted a trade off among area, flexibility and consumption. This chip joins several SMD elements (storage capacitors, RF diodes and coils) to form a hybrid implantable system. The overall size once encapsulated in silastic is expected to be about 1 cm³ including a flat air-cored power coil and a very small cylindrical magnetic-cored transmitter coil. The telemetric system presented here meets the following specifications: (1) bi-directional digital communication with inlink rates at 250 kbps and outlink rates at 500 kbps, (2) outlink PCM, (3) ASK inlink and BPSK outlink modulation, (4) PWM-RZ inlink and outlink bit codification and (5) efficient RF power transference at distances up to 10 mm and lateral misalignment tolerance of ± 10 mm.

RESULTS A first IC prototype containing some telemetric modules (no recording circuitry) has already been fabricated and successfully tested within a non-implantable telemetric system. A new totally implantable IC here presented has been designed and submitted to fabrication. Test will be covered in early 97 so electronic chip results and telemetric system performances will be available before the ISOB meeting.

DISCUSSION Special efforts on increasing the power efficiency will be taken in future, by introducing an induced secondary voltage closed-loop control and by increasing the integration scale towards submicron structures.