WM8961GEFLSLASHV datasheet(26/116 Pages) WOLFSON

26 / 116 page

WM8961

Pre-Production

PP, August 2009, Rev 3.1

The internal MICBIAS circuitry is shown in Figure 14.

The maximum source current capability for MICBIAS is 2mA. The external biasing resistors therefore

must be large enough to limit the MICBIAS current to 2mA.

Figure 14 Microphone Bias Schematic

ANALOGUE TO DIGITAL CONVERTER (ADC)

The WM8961 uses stereo 24-bit, 128x over-sampled sigma-delta ADCs. The use of multi-bit feedback

and high over-sampling rates reduce the effects of jitter and high frequency noise. The ADC Full Scale

input level is proportional to AVDD. With a 1.8V supply voltage, the full scale level is 0.5Vrms. Any

voltage greater than full scale may overload the ADC and cause distortion.

The ADCs are enabled by the ADCL/R register bit. Note that when disabling the ADC, the digital

volume control LADCVOL/RADCVOL[7:0] (R21 (15h)) should be muted (set to 00h), before clearing

ADCL or ADCR to 0. This ensures that the last ADC code does not appear at the Audio Interface

(ADCDAT) pin when ADCL/R are cleared.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R25 (19h)

Power

management (1)

ADCL

Enable ADC left channel:

0 = ADC disabled

1 = ADC enabled

ADCR

Enable ADC right channel:

0 = ADC disabled

1 = ADC enabled

Table 9 ADC Enable Control

ADCDIV determines the ADC operating clock. The output of ADCDIV should be configured to output a

clock of 256fs. The 256fs output of ADCDIV is further divided such that the ADC operates at 128fs.

WM8961GEFL/V Datasheet(PDF) 26 Page - Wolfson Microelectronics plc