A control system for a low power bidirectional front-end for resonating sensors

In this paper, we propose a digital control system to automatize the operation of a bidirectional front-end for resonating sensors. Due to the simplicity, the control system is power conservative and compact. The main source of power consumption in the bidirectional front-end is the amplifier used to read-out the sensor. Power can be saved by turning off the amplifier after a few periods of the oscillating signal, which is enough to detect the resonant frequency of the sensor. The concept was initially proved by performing simulations in SPICE by using AMS-350nm CMOS technology model. A prototype was realized with discrete components on a PCB and tested with a power supply of 5V. The reading cycle was fixed at 10kHz and a RLC load has been used as model of a MEMS resonant sensor. The values for the RLC components used for the tests are 100Ω, 270pF, 10mH. The nominal power consumption of the front-end without the support of the sleeping mode is 1.7mW while the sleeping mode with reading one oscillation period reduces the power dissipation to 270µW(15.88% of 1.7mW).