An energy-efficient ASIC with real-time work-on-demand for wireless body sensor network

This paper presents an energy efficient ASIC design with the capability of real-time work-on-demand, targeting on the applications of wireless body sensor network (WBSN), especially on those for medical and heath purposes. Application specific requirements have been reviewed. A novel type of sensor node architecture is proposed with a hybrid of active/passive transceivers. The passive RF receiver with zero standby current gives the WBSN nodes the real capability of work-on-demand which is not allowed in previous architectures. A power management module with an optimized power mode control scheme has also implemented to provide various supply voltages for the sensor nodes, and in addition this module can provide the sensor nodes a flexible power mode control for the purpose of energy saving. An ultra-low-power MCU which supports the proposed architecture has been integrated in the ASIC, which can perform the functions of media access, signal flow control and networking. The proposed architecture has been verified through FPGA experiments, and the ASIC has been designed and fabricated using a standard 0.18 um CMOS process. The designed ASIC occupies a die area of 2 mm times 2.5 mm. The digital core of this ASIC has 72.8 K equivalent gate counts excluding the memories. A typical WBSN sensor node can be built with this ASIC in together with a commercial RF transceiver, the sensor parts and some other components, and our ASIC can serve as the main control part for such a node.