WM8941 datasheet(43/96 Pages) WOLFSON

43 / 96 page

Pre Production

WM8941

PP, Rev 3.3, December 2007

OUTPUT SIGNAL PATH

The WM8941 output signal paths consist of digital application filters, up-sampling filters, a Hi-Fi

DAC, analogue mixers, speaker and mono output drivers. The digital filters and DAC are enabled by

bit DACEN. The mixers and output drivers can be separately enabled by individual control bits (see

Analogue Outputs). Thus it is possible to utilise the analogue mixing and amplification provided by

the WM8941, irrespective of whether the DACs are running or not.

The WM8941 DAC receives digital input data on the DACDAT pin. The digital filter block processes

the data to provide the following functions:

•

Digital volume control

•

A digital peak limiter.

•

Sigma-Delta Modulation

The high performance sigma-delta audio DAC converts the digital data into an analogue signal.

Figure 19 DAC Digital Filter Path

The analogue output from the DAC can then be mixed with the AUX analogue input and the ADC

analogue input. The mix is fed to the output drivers, SPKOUTP/N, and MONOOUT.

MONOOUT: can drive a 16

Ω or 32Ω headphone or line output or can be a buffered version of VMID

(When MONOMUTE=1).

SPKOUTP/N: can drive a 16

Ω or 32Ω stereo headphone or stereo line output, or an 8Ω BTL mono

speaker.

DIGITAL HI-FI DAC VOLUME CONTROL

The signal volume from each Hi-Fi DAC can be controlled digitally. The gain and attenuation range

is –127dB to 0dB in 0.5dB steps. The level of attenuation for an eight-bit code X is given by:

0.5

× (X-255) dB for 1 ≤ X ≤ 255; MUTE for X = 0

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R11

DAC Digital

Volume

7:0

DACVOL

[7:0]

11111111

( 0dB )

DAC Digital Volume Control

0000 0000 = Digital Mute

0000 0001 = -127dB

0000 0010 = -126.5dB

... 0.5dB steps up to

1111 1111 = 0dB

Table 29 DAC Volume

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