A SoC with 3.9mW 3Mbps UHF transmitter and 240μW MCU for capsule endoscope with bidirectional communication

An ultra-low-power system-on-a-chip (SoC) for wireless capsule endoscopes has been implemented, providing bidirectional communication between the capsule and the external data logger. The SoC is composed of a programmable UHF band transceiver with 3Mbps MSK transmitting and 64kbps OOK receiving, a 1.2V MCU with a dedicated image compressor, multiple on-chip voltage regulators, and etc. The SoC can work with a power supply down to 2.5V. The 3Mbps transmitter working at 400MHz band consumes only 3.9mW power, and the MCU draws only 200μ A current from 1.2V supply. Fabricated in 0.18μm CMOS, the SoC occupies a die area of 13.3mm² including the I/O pads. A capsule endoscope prototype has been developed using this SoC plus an image sensor. With this SoC, the capsule endoscope can capture 512*512 gastrointestinal images with a frame rate of up to 3 fps.