Scheme to achieve robustness to electromagnetic interference in inertial sensors

摘要

A capacitive sensor system and method resistant to electromagnetic interference is disclosed. The system includes a capacitive core, differential amplifier with inverting and non-inverting inputs, capacitive paths, and chopping system. Core can include inputs and outputs coupled to variable capacitors, and common nodes coupling variable capacitors. Capacitive paths couple core outputs to amplifier inputs. When chopping system is high, one polarity voltage is applied to core inputs, a first core output is coupled to the inverting input and a second core output is coupled to the non-inverting input. When the chopping system is low, opposite polarity voltage is applied to core inputs, and core output to amplifier input couplings are flipped. Capacitive paths can include bond wires. Chopping system can be varied between high and low at frequencies that smear noise away from a frequency band of interest, or that smear noise substantially evenly across a wide frequency range.

主权项

1. A method for achieving robustness to electromagnetic interference in an inertial sensor system comprising a first signal path susceptible to electromagnetic interference and a second signal path susceptible to electromagnetic interference, the method comprising:
switchably coupling the first signal path of the inertial sensor system to the inputs of a differential amplifier, the differential amplifier including an inverting input and a non-inverting input; switchably coupling the second signal path of the inertial sensor system to the inputs of the differential amplifier; switching a chopping system between a high state and a low state to control electromagnetic interference in the inertial sensor system, when the chopping system is in the high state:
applying a first polarity voltage to a first input of the inertial sensor system,applying a second polarity voltage to a second input of the inertial sensor system, the second polarity voltage having substantially the same magnitude and opposite polarity as the first polarity voltage,coupling the first signal path of the inertial sensor system to the inverting input of the differential amplifier; andcoupling the second signal path of the inertial sensor system to the non-inverting input of the differential amplifier; and when the chopping system is in the low state,
applying the second polarity voltage to the first input of the inertial sensor system,applying the first polarity voltage to the second input of the inertial sensor system,coupling the first signal path of the inertial sensor system to the non-inverting input of the differential amplifier; andcoupling the second signal path of the inertial sensor system to the inverting input of the differential amplifier.