Patent ID: 8942389
Filing Date: 2015-01-27
Classification: H04R

Abstract:
1. A method of adjusting a MEMS microphone to account for variations in manufacturing processes, the MEMS microphone including a gap of an undetermined thickness between a movable membrane and a stationary backplate, the method comprising: applying a first voltage to a power supply voltage pad to enter a normal operation mode; applying a first serial binary input to a second pad while in the normal operation mode, wherein a logic layer of the MEMS microphone performs a first operation unrelated to adjusting the bias voltage and the gain based on the first serial binary input while operating in the normal operation mode; applying a second voltage, the second voltage higher than the first voltage, to the power supply voltage pad to enter a trim mode, applying a first sound level to the MEMS microphone; evaluating a sensitivity of the MEMS microphone based on a digital output of the MEMS microphone when the first sound level is applied; adjusting a bias voltage of the MEMS microphone by applying a binary trim code to the second pad as a second serial binary input when operating in the trim mode when the sensitivity does not meet a defined sensitivity protocol, wherein the binary trim code indicates an adjustment to the bias voltage of the MEMS microphone and wherein the trim module adjusts the bias voltage of the MEMS microphone according to the binary trim code; applying a second sound level to the MEMS microphone, the second sound level having a greater amplitude than the first sound level; evaluating a stability of the MEMS microphone based on a digital output of the MEMS microphone when the second sound level is applied; and when the stability does not meet a defined stability protocol, lowering the bias voltage and making a corresponding increase in a gain applied to the movable membrane and the stationary backplate by applying a second binary trim code as a third serial binary input to the second pad when operating in the trim mode, wherein the trim module adjusts the gain and the bias voltage of the MEMS microphone according to the second binary trim code.