Power management circuits for a 15-μA, implantable pressure sensor

A custom IC for wireless bladder pressure sensing incorporates power-management circuitry to limit the active time of the instrumentation circuitry and to minimize telemetry rate. Instrumentation circuits are operated with low duty factors in a pipelined manner to generate 100-Hz pressure samples. Telemetry rate is adapted according to sample activity, which is measured using a 2^nd-order FIR filter. Measured results indicate that the number of transmitted samples is less than 5% of those acquired, resulting in an average telemetry rate of 1.5 Hz and corresponding current of 0.6 μA. A low-power regulator and clock oscillator set a baseline current draw of 7.5 μA while instrumentation and digital circuits consume an average of 4.7 μA, for a total average consumption of just 12.8 μA.