25 to 300 Degree celsius 80bps acoustic transmitter based on crystal-less temperature-independent frequency reference with differential modulation for drilling noise power cancellation

An acoustic transmitter employing crystal-less temperature-independent frequency reference and differential modulation has been realized in 1um SOI CMOS process. A temperature-independent switched capacitor based FVC is incorporated within an FLL to provide a stable frequency reference, which in turns generates the acoustic carriers. Differential modulation is proposed to allow drilling noise power cancellation at the receiver end. The FLL generates 3.3MHz output with an inaccuracy less than 2.85% over temperature range of 25 to 300 degree Celsius using digital trimming. Consuming 11mW under 5V supply, the transmitter achieves a data rate of 80bps while occupying an area of 25mm².