WM8903 datasheet(42/178 Pages) WOLFSON

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WM8903

Production Data

PD, Rev 4.5, June 2012

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R164 (A4h)

Clock Rate

Test 4

ADC_DIG_MIC

Enables Digital Microphone mode.

0 = Audio DSP input is from ADC

1 = Audio DSP input is from digital

microphone interface

Table 9 Digital Microphone Interface Control

Note that, in addition to setting the ADC_DIG_MIC bit as described in Table 9, the pins

GPIO1/DMIC_LR and GPIO2/DMIC_DAT must also be configured to provide the digital microphone

interface function. See “General Purpose Input/Output (GPIO)” for details.

ANALOGUE-TO-DIGITAL CONVERTER (ADC)

The WM8903 uses two 24-bit, 128x oversampled sigma-delta ADCs. The use of multi-bit feedback

and high oversampling rates reduces the effects of jitter and high frequency noise. An oversample

rate of 64x can also be supported - see “Clocking and Sample Rates” for details. The ADC full-scale

input level is proportional to AVDD - see “Electrical Characteristics”. Any input signal greater than full

scale may overload the ADC and cause distortion.

The ADCs are enabled by the ADCL_ENA and ADCR_ENA register bits.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R18 (12h)

Power

Management

ADCL_ENA

Left ADC Enable

0 = disabled

1 = enabled

ADCR_ENA

Right ADC Enable

0 = disabled

1 = enabled

Table 10 ADC Enable Control

ADC DIGITAL VOLUME CONTROL

The output of the ADCs can be digitally amplified or attenuated over a range from -71.625dB to

+17.625dB in 0.375dB steps. The volume of each channel can be controlled separately. The gain for

a given eight-bit code is detailed in Table 12.

The ADC_VU bit controls the loading of digital volume control data. When ADC_VU is set to 0, the

ADCL_VOL or ADCR_VOL control data is loaded into the respective control register, but does not

actually change the digital gain setting. Both left and right gain settings are updated when a 1 is

written to ADC_VU. This makes it possible to update the gain of both channels simultaneously.

WM8903 Datasheet(PDF) 42 Page - Wolfson Microelectronics plc

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