WM8903 datasheet(174/178 Pages) WOLFSON

174 / 178 page

WM8903

Production Data

PD, Rev 4.5, June 2012

174

MIC DETECTION SEQUENCE USING MICBIAS CURRENT

This section details an example sequence which summarises how the host processor can configure

and detect the events supported by the MICBIAS current detect function (see “Electret Condenser

Microphone Interface”):



Mic insertion/removal



Hook switch press/release

Figure 68 shows an example of how the MICBIAS current flow varies versus time, during mic

insertion and hook switch events. The Y axis is annotated with the Mic detection thresholds, and the

X axis is annotated with the stages of an example sequence as detailed in Table 86, to illustrate how

the host processor can implement mic insertion and hook switch detection.

The sequence assumes that the microphone insertion and hook switch detection functions are

monitored by polling the interrupt flags using the control interface. Note that the maximum mechanical

bounce times for mic insertion and removal must be fully understood by the software programmer.

A GPIO pin could be used as an alternative mechanism to monitor the MICBIAS detection functions.

This enables the host processor to detect mechanical bounce at any time.

Figure 68 Mic Insert and Hook Switch Detect: Example MICBIAS Current Plot

WM8903 Datasheet(PDF) 174 Page - Wolfson Microelectronics plc