WM8941 datasheet(50/96 Pages) WOLFSON

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WM8941

Pre Production

PP, Rev 3.3, December 2007

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R49

VROI

VREF (AVDD/2) to analogue output

resistance

0: approx 1k

Ω

1: approx 30 k

Ω

Table 39 Disabled Outputs to VREF Resistance

A dedicated buffer is available for tying off unused analogue I/O pins as shown in Figure 21. This

buffer can be enabled using the BUFIOEN register bit.

Table 40 summarises the tie-off options for the speaker and mono output pins.

Figure 21 Unused Input/Output Pin Tie-off Buffers

MONOEN/

SPKN/PEN

VROI

OUTPUT CONFIGURATION

1kΩ tieoff to AVDD/2

30kΩ tieoff to AVDD/2

Output enabled (DC level=AVDD/2)

Table 40 Unused Output Pin Tie-off Options

OUTPUT SWITCH

When the device is configured with a 2-wire interface the CSB/GPIO pin can be used as a switch

control input to automatically disable the speaker outputs and enable the mono output. As an

example, when a line is plugged into a jack socket. In this mode, enabled by setting GPIOSEL=001,

pin CSB/GPIO switches between mono and speaker outputs (e.g. when pin 12 is connected to a

mechanical switch in the headphone socket to detect plug-in). The GPIOPOL bit reverses the

polarity of the CSB/GPIO input pin. In 3-wire control mode the GPIO pin can be use in the same

way.

Note that the speaker outputs and the mono output must be enabled for this function to work (see

Table 41). The GPIO has 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, enabled using the SLOWCLKEN register bit.

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