WM1811A datasheet(69/328 Pages) WOLFSON

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Production Data

WM1811A

PD, November 2013, Rev 4.1

ULTRASONIC (4FS) AIF OUTPUT MODE

The WM1811A provides an ultrasonic mode on the output paths of the AIF1 audio interface. The

ultrasonic mode enables high frequency signals (such as ultrasonic microphone signals) to be output.

Ultrasonic mode is enabled on AIF1 using the AIF1ADC_4FS register bit. When the ultrasonic mode is

selected, the AIF1output sample rate is increased by a factor of 4. For example, a 48kHz sample rate

will be output at 192kHz in ultrasonic mode.

Ultrasonic mode is only supported in AIF Master mode and uses the ADCLRCLK output (not the

LRCLK). When ultrasonic mode is enabled, the AIF1 must be configured in Master mode, as

described in “Digital Audio Interface Control”.See “General Purpose Input/Output” to configure the

GPIO1 pin as ADCLRCLK1.The ADCLRCLK1 rate is controlled as described in “Digital Audio

Interface Control”.

When ultrasonic mode is enabled, the audio band filtering and digital volume controls (see “Digital

Volume and Filter Control”) are bypassed on the affected output paths.

The Dynamic Range Control (DRC) function is not available on the AIF1output signal paths in

ultrasonic mode. Note, however, that the DRC is still available on the AIF input paths in this case.

The ultrasonic (4FS) signal paths are illustrated in Figure 20. The AIF1ADC_4FS register bit is defined

in Table 24.

Figure 20 Ultrasonic (4FS) Signal Paths

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1040 (0410h)

AIF1 ADC1

Filters

AIF1ADC_4FS

Enable AIF1ADC ultrasonic mode

(4FS) output, bypassing all AIF1

baseband output filtering

0 = Disabled

1 = Enabled

Table 24 Ultrasonic (4FS) Mode Control

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