Switchable attenuation circuit for MEMS microphone systems

摘要

A switch control circuit monitors a signal produced by a MEMS or other capacitor microphone. When a criterion is met, for example when the amplitude of the monitored signal exceeds a threshold or the monitored signal has been clipped or analysis of the monitored signal indicates clipping is imminent or likely, the switch control circuit operates one or more switches so as to selectively connect one or more capacitors to a signal line from the microphone, i.e., so as to connect a selected capacitance to the signal line to attenuate the signal from the microphone and, therefore, avoid clipping. The switches may be MOSFET, MEMS or other types of switches co-located with the microphone in a common semiconductor package. Similarly, the capacitors, a circuit that processes the signals from the microphone and/or the switch control circuit may be co-located with the microphone in a common semiconductor package.

主权项

1. A microphone system comprising:
a movable structure movable in response to an acoustic signal establishing a variable MEMS capacitance with respect to an electrode, the movable structure and the electrode forming a MEMS microphone, the movement of the movable structure causing a signal to be generated, the signal being carried on a conductive line; a circuit configured to process the signal; a capacitor coupling the conductive line to ground upon detection of the processed signal exceeding a criterion by the circuit; and a switch selectively operable to connect to the conductive line so as to attenuate the signal before the signal is processed by the circuit, wherein the capacitor has associated therewith a capacitance that in combination with the variable MEMS capacitance serves as a signal divider causing the signal on the conductive line to be attenuated.