Capacitive MEMS sensor detection circuit

Abstract

The invention discloses a capacitive MEMS sensor detection circuit. The circuit is used to detect the displacement change of a pole plate of a MEMS. The capacitive MEMS sensor detection circuit mainly comprises a high-frequency oscillation circuit generating sine waves, two C-1 / V detection circuits, a differential amplification circuit, a phase shift network, a multiplication circuit, a low-pass filter circuit, and an amplification output circuit. The high-frequency oscillation circuit generates three in-phase sine waves, two of which are supplied to the two C-1 / V detection circuits to detect C-1 change caused by the displacement of the pole plate of the MEMS. The differential amplification circuit is used to eliminate the influence of body capacitance and improve the precision of detection. The phase shift network is used to compensate phase shift through the C-1 / V circuits and ensure that the signals input to the multiplication circuit are of the same phase. The low-pass filter circuit filters high harmonics of signals output by a multiplier and extracts the signals reflecting the displacement change of the pole plate of the MEMS so as to complete detection of the displacement change of the pole plate of the MEMS.

Description

technical field [0001] The invention relates to the field of weak signal detection of MEMS sensors, and more particularly relates to a capacitive MEMS sensor detection circuit. Background technique [0002] In recent years, with the continuous promotion of capacitive MEMS applications, new requirements have been put forward for MEMS interface circuits. However, most of the interface circuits of capacitive MEMS at this stage are based on C-based measurement circuits. Only when the static plate spacing is much larger than the dynamically changing spacing can the nonlinearity be reduced to a certain extent, otherwise the nonlinearity is very obvious. At the same time, the chopper stabilization method and double correlation sampling method commonly used at present have certain limitations on MEMS capacitance detection: the chopper stabilization method, the relative delay of the circuit will have a great impact on the measurement, and the square wave brings Harmonics will cause ...

AI Technical Summary

Problems solved by technology

However, most of the interface circuits of capacitive MEMS at this stage are based on C-based measurement circuits. Only when the distance between the plates is much larger than the dynamic distance in static state can the nonlinearity be reduced to a certain extent, otherwise the nonlinearity is very obvious.

At the same time, the chopper stabilization method and double correlation sampling method commonly used at present have certain limitations on MEMS capacitance detection: the chopper stabilization method, the relative delay of the circuit will have a great impact on the measurement, and the square wave brings Harmonics will cause the noise in each frequency band to stack in the baseband signal; the double correlation sampling method has improved, but there are still limitations such as clock feedthrough, charge injection, and insufficient input bandwidth for noise aliasing

At the same time, the above capacitance detection method will produce a large error due to the parasitic effect at the interface.

Images