公开(公告)号：US20190306632A1

公开(公告)日：2019-10-03

申请号：US15940033

申请日：2018-03-29

Applicant: Cirrus Logic International Semiconductor Ltd.

Inventor： Timothy J. DUPUIS ,  Vivek SARAF ,  Axel THOMSEN

IPC: H04R19/04 ,  H04R3/00

Abstract: A bias circuit for a capacitive sensor may include a variable impedance element coupled to a capacitor of the capacitive sensor wherein an impedance of the variable impedance element is varied in accordance with a temperature associated with the bias circuit and an active feedback circuit coupled between the variable impedance element and an output of a processing circuit for processing a signal generated by the capacitive sensor and configured to drive the variable impedance element to force a direct-current (DC) voltage level of an output of the capacitive sensor to a desired voltage.

公开(公告)号：US20190306621A1

公开(公告)日：2019-10-03

申请号：US15939994

申请日：2018-03-29

Applicant: Cirrus Logic International Semiconductor Ltd.

Inventor： Ian Johnson SMITH ,  James Thomas DEAS ,  Vivek SARAF

IPC: H04R3/00 ,  H04R19/04

Abstract: The present disclosure relates to a protection system for protecting a MEMS transducer of a MEMS device from electrostatic capture, wherein the MEMS transducer is operable in a normal-sensitivity, mode and in a reduced-sensitivity mode. The protection system comprises: an overload detector for detecting an overload condition arising as a result of an excessive sound pressure level at the MEMS transducer; a signal estimator configured to generate an estimate of a sound pressure level at the MEMS transducer; and a controller configured, in response to detection by the overload detector of an overload condition, to: disable an output of the MEMS transducer; and after a delay of a first predetermined period of time: cause the MEMS transducer to operate in the reduced-sensitivity mode; enable the output of the MEMS transducer; and cause the MEMS transducer to return to the normal-sensitivity mode if the estimate of the sound pressure level generated by the signal estimator while the MEMS transducer is operating in the reduced-sensitivity mode is below a safe sound pressure level threshold for a second predetermined period of time.