WM8962 Datasheet, PDF (41/295 Pages) Wolfson Microelectronics plc – Ultra-Low Power Stereo CODEC with Audio Enhancement DSP, 1W Stereo Class D Speaker Drivers and Ground Referenced Headphone Drivers

WM8962
The detection of these events is bandwidth limited for best noise rejection, and is subject to detection
delay time tDET, as specified in the “Electrical Characteristics” section. Provided that the MICDET_THR
field has been set appropriately, each insertion or removal event is guaranteed to be detected within
the delay time tDET.
It is likely that the microphone socket contacts will have mechanical “bounce” when a microphone is
inserted or removed, and hence the resultant control signal will not be a clean logic level transition.
Since tDET has a range of values, it is possible that the interrupt will be generated before the
mechanical “bounce” has ceased. Hence after a mic insertion or removal has been detected, a time
delay should be applied before re-configuring the MICD_IRQ_POL bit. The maximum possible
mechanical bounce times for mic insertion and removal must be understood by the software
programmer.
Utilising a GPIO pin to monitor the steady state of the microphone detection function does not change
the timing of the detection mechanism, so there will also be a delay tDET before the signal changes
state. It may be desirable to implement de-bounce in the host processor when monitoring the state of
the GPIO signal.
Microphone hook switch operation is detected when the MICBIAS current exceeds the Short Circuit
Detect threshold set by MICSHORT_THR. Using the digital filtering, the hook switch detection event is
only signalled if the MICSHORT_THR threshold condition has been met for 10 consecutive
measurements.
When the MICSCD_IRQ_POL interrupt polarity bit is set to 0, then hook switch operation will cause
the MICSCD_EINT interrupt status register to be set. (See “Interrupts” for details of these register
bits.)
For detection of microphone removal, the MICSCD_IRQ_POL bit should be set to 1. When the
MICSCD_IRQ_POL interrupt polarity bit is set to 1, then hook switch release will cause the
MICSCD_EINT interrupt status register to be set.
The hook switch detection measurement frequency and the detection delay time tSHORT are detailed in
the “Electrical Characteristics” section.
The WM8962 Interrupt function is described in the “Interrupts” section. Example control sequences for
configuring the Interrupts functions for MICBIAS current detection events are described in the
“Applications Information” section.
A clock is required for the digital filtering function. This requires:
 MCLK is present or the FLL is selected as the SYSCLK source in free-running mode
 SYSCLK_ENA = 1
Any MICBIAS Current Detect event (accessory insertion/removal or hookswitch press/release) which
happens while one or more of the clocking criteria is not satisfied (for example during a low power
mode where the CPU has disabled MCLK) will still be detected, but only after the clocking conditions
are met. An example is illustrated in Figure 16, where the mic is inserted while MCLK is stopped.
Note that the interrupts and digital filtering can be supported in the absence of an external clock by
using the FLL in free-running mode and selecting the FLL as the clock source, as described in
“Clocking and Sample Rates”.
Rev 4.3
41