WM8972LEFLSLASHR datasheet(21/49 Pages) WOLFSON

21 / 49 page

Preliminary Technical Data

WM8972L

PTD Rev 2.2 June 2004

OUTPUT SIGNAL PATH

The WM8972L output signal paths consist of digital filters, a DAC, analogue mixers and output

drivers. The digital filters and DAC are enabled when the WM8972L is in ‘playback only’ or ‘record

and playback’ mode. 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 WM8972L, irrespective of whether the DAC is running or not.

The WM8972L receives digital input data on the DACDAT pin. The digital filter block processes the

data to provide the following functions:

•

Digital volume control

•

Graphic equaliser and Dynamic Bass Boost

•

Sigma-Delta Modulation

A high performance sigma-delta audio DAC converts the digital data into two analogue signals (left

and right). These can then be mixed with analogue signals from the INPUT1+/2+ and INPUT1-/2-

pins, and the mix is fed to the output drivers, OUT+/OUT-, OUT2 and MONOOUT.

•

OUT2: can drive a 16

Ω or 32Ω headphone or line output.

•

OUT+/OUT-: can drive a 16

Ω or 32Ω headphone or line output, or an 8Ω mono speaker.

•

MONOOUT: can drive a mono line output or other load down to 10k

Ω

DIGITAL DAC VOLUME CONTROL

The signal volume from the DAC can be controlled digitally, in the same way as the ADC volume

(see Digital ADC Volume Control). 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

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

DACVOL control data is loaded into an intermediate register, but the actual gain does not change.

The gain settings are updated simultaneously when DVU is set to 1.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

DVU

DAC Volume Update

0 = Store DACVOL in intermediate

latch (no gain change)

1 = Update gains

R10 (0Ah)

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 10 Digital Volume Control

GRAPHIC EQUALISER

The WM8972L has a digital graphic equaliser and adaptive bass boost function. This function

operates on digital audio data before it is passed to the audio DAC. Bass enhancement can take two

different forms:

•

Linear bass control: bass signals are amplified or attenuated by a user programmable

gain. This is independent of signal volume, and very high bass gains on loud signals

may lead to signal clipping.

•

Adaptive bass boost: The bass volume is amplified by a variable gain. When the bass

volume is low, it is boosted more than when the bass volume is high. This method is

recommended because it prevents clipping, and usually sounds more pleasant to the

human ear.

Treble control applies a user programmable gain, without any adaptive boost function. Bass and

treble control are completely independent with separately programmable gains and filter

characteristics.

WM8972LEFL/R 数据表(PDF) 21 Page - Wolfson Microelectronics plc

WM8972LEFL/R 数据表(HTML) 21 Page - Wolfson Microelectronics plc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

数据表下载