Integrated GMR magnetic switch for implantable medical devices

This paper presents an integrated GMR magnetic switch designed for implantable medical devices (IMDs). Because of GMR´s high sensitivity and great linearity, this magnetic switch´s operation error band is much smaller than Hall-effect and AMR switches, and can operate with a magnetic field as low as 5.6|Oe|. Same as the traditionally used dry reed, GMR switch detects the magnetic signal that is transmitted from a short distance. However, GMR switch could integrate GMR sensor with the CMOS circuits together. Moreover, by employing a hysteresis comparator and a low duty-cycle oscillator, this switch also features high anti-disturbance ability, and very low power consumption which is only about 1μW averagely at 37°C, the normal body temperature. The designed switch device is much smaller as compared with other magnetic switchs including dry reed or the wireless one based on passive RF receiver. The circuit is designed and simulated by using the model for CSMC 0.5μm technology.