A High-Resolution Accelerometer With Electrostatic Damping and Improved Supply Sensitivity

In this paper, a charge-balancing accelerometer is presented. A hybrid interface topology is utilised to achieve high resolution, high linearity and low power supply sensitivity. The accelerometer consists of a micromechanical sensor element, a self-balancing bridge (SBB) open-loop readout, AC force feedback and
$\Delta \Sigma$
ADC. The SBB converts acceleration to ratiometric voltage. The ratiometric output of the SBB is converted to the digital domain by the ADC. In order to achieve high resolution, a micromechanical sensor element with a high quality factor, Q, is utilised. The AC force feedback is used for damping the high Q to get a low settling time. The sensor interface is fabricated in a standard 0.35
$\mu$
m CMOS process. The fabricated chip has an area of 6.66 mm
$^2$
and consumes 1 mA at a nominal supply voltage of 3.6 V. The sensor has a maximum DC nonlinearity of 1.3% over the commercial temperature range with an input range of
${\pm} $
1.15 g. The noise floor of the sensor is around 2
$\mu{\rm g}/\sqrt{{\rm Hz}}$
and the signal bandwidth is 200 Hz. The bias instability is 13
$\mu$
g and the sensor gain variation is less than 5% in the 3–3.6 V supply range.