This paper presents a wireless micro-stimulating ASIC for cochlear prosthesis application, to restore auditory function in profoundly deaf individuals. A new wideband frequency-shift keying (FSK) demodulator is designed to guarantee the high bandwidth of the digital data transmission chain. The demodulator circuit derives a constant frequency clock from FSK carrier directly, and uses this clock to sample the data bits. The circuit is experimentally tested at the stimulus rate up to 75k pulses per second with transmission speed of 2.5Mbps while receiving a 5M/10MHz FSK carrier signal. The whole circuit occupies 7.5 mm2in a 0.6 μm, 2M/2P, standard CMOS process, and consumes 12.5mW at 5V.