WM8985GEFLSLASHR datasheet(87/121 Pages) WOLFSON

87 / 121 page

Production Data

WM8985

PD, Rev 4.6, July 2009

For further details of the jack detect operation see the OUTPUT SWITCHING section.

OUTPUT SWITCHING (JACK DETECT)

When the device is operated using a 2-wire interface the CSB/GPIO1 pin can be used as a switch

control input to automatically disable one set of outputs and enable another; the most common use

for this functionality is as jack detect circuitry. The L2/GPIO2 and R2/GPIO3 pins can also be used

for this purpose.

The GPIO pins have an internal de-bounce circuit when in this mode in order to prevent the output

enables from toggling multiple times due to input glitches. This de-bounce circuit is clocked from a

slow clock with period 221 x MCLK and is enabled by the SLOWCLKEN bit.

Notes:

The SLOWCLKEN bit must be enabled for the jack detect circuitry to operate.

The GPIOPOL bit is not relevant for jack detection, it is the signal detected at the pin which is

used

Switching on/off of the outputs is fully configurable by the user. Each output, OUT1, OUT2, OUT3

and OUT4 has 2 associated enables. OUT1_EN_0, OUT2_EN_0, OUT3_EN_0 and OUT4_EN_0

are the output enable signals which are used if the selected jack detection pin is at logic 0 (after de-

bounce). OUT1_EN_1, OUT2_EN_1, OUT3_EN_1 and OUT4_EN_1 are the output enable signals

which are used if the selected jack detection pin is at logic 1 (after de-bounce).

The jack detection enables operate as follows:

All OUT_EN signals have an AND function performed with their normal enable signals (in Table 39).

When an output is normally enabled as per Table 39, the selected jack detection enable (controlled

by selected jack detection pin polarity) is set 0; it will turn the output off. If the normal enable signal is

already OFF (0), the jack detection signal will have no effect due to the AND function.

During jack detection if the user desires an output to be un-changed whether the jack is in or not,

both the JD_EN settings, i.e. JD_EN0 and JD_EN1, should be set to 0000.

If jack detection is not enabled (JD_EN=0), the output enables default to all 1’s, allowing the outputs

to be controlled as normal via the normal output enables found in Table 39.

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