The Development of a RFID Based Mixed Signal ASIC for the Wireless Measurement of Intraocular Pressure

The initial development of a wireless transponder for an IOP monitor capable of performing uninterrupted measurement for 24 hours a day is presented. This work eliminates the need for a permanent power and data link between an external reader and the ophthalmic implant, thereby greatly reducing the required patient interaction. The transponder consists of a custom developed Application Specific Integrated Circuit (ASIC), pressure sensor, FRAM memory, and a super capacitor based power module. The ASIC was fabricated using a 0.5-μm CMOS process and implements a RFID-based inductively coupled front-end operating at 13.56 MHz. The data logging circuit is designed to sample pressure once every 10 minutes. Power consumption of the transponder operating at VDD = 2.8 V and FCLK = 140 kHz is estimated at 30 μA during data logging read/write phases and 12 μA for timing operations.