WM8983GEFLSLASHV datasheet(79/124 Pages) WOLFSON

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Production Data

WM8983

PD, Rev 4.3, May 2010

UNUSED ANALOGUE INPUTS/OUTPUTS

Whenever an analogue input/output is disabled, it remains connected to a voltage source (either

AVDD1/2 or 1.5xAVDD1/2 as appropriate) through a resistor. This helps to prevent pop noise when

the output is re-enabled. The resistance between the voltage buffer and the output pins can be

controlled using the VROI control bit. The default impedance is low, so that any capacitors on the

outputs can charge up quickly at start-up. If a high impedance is desired for disabled outputs, VROI

can then be set to 1, increasing the resistance to about 30k

Ω.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R49

VROI

VREF (AVDD1/2 or 1.5xAVDD/2) to

analogue output resistance

0: approx 1k

1: approx 30 k

Table 53 Disabled Outputs to VREF Resistance

A dedicated buffer is available for biasing unused analogue I/O pins as shown in Figure 41. This

buffer can be enabled using the BUFIOEN register bit.

If the SPKBOOST, OUT3BOOST or OUT4BOOST bits are set then the relevant outputs will be tied

to the output of the DC level shift buffer at 1.5xAVDD/2 when disabled.

Figure 41 summarises the bias options for the output pins.

Figure 41 Unused Input/Output Pin Tie-off Buffers

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