WM8972L datasheet(28/49 Pages) WOLFSON

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WM8972L

Preliminary Technical Data

PTD Rev 2.2 June 2004

SPEAKER OUTPUT

OUT+ and OUT- can differentially drive a mono 8

Ω speaker as shown below.

Figure 9 Speaker Output Connection

The OUT- channel is inverted by setting the OUTINV bit, so that the signal across the loudspeaker is

the sum of OUT+ and OUT- signals.

LINE OUTPUT

The analogue outputs OUT+/OUT- can be used as line outputs. Recommended external components

are shown below.

Figure 10 Recommended Circuit for Line Output

The DC blocking capacitors and the load resistance together determine the lower cut-off frequency,

fc. Assuming a 10 kOhm load and C1, C2 = 1

µF:

fc = 1 / 2

π (RL+R1) C1 = 1 / (2π x 10.1kΩ x 1µF) = 16 Hz

Increasing the capacitance lowers fc, improving the bass response. Smaller values of C1 and C2 will

diminish the bass response. The function of R1 and R2 is to protect the line outputs from damage

when used improperly.

DIGITAL AUDIO INTERFACE

The digital audio interface is used for inputting DAC data into the WM8972L and outputting ADC data

from it. It uses five pins:

•

ADCDAT: ADC data output

•

ADCLRC: ADC data alignment clock

•

DACDAT: DAC data input

•

ADCLRC: DAC data alignment clock

•

BCLK: Bit clock, for synchronisation

The clock signals BCLK, ADCLRC and DACLRC can be outputs when the WM8972L operates as a

master, or inputs when it is a slave (see Master and Slave Mode Operation, below).

Four different audio data formats are supported:

•

Left justified

•

Right justified

•

DSP mode

All four of these modes are MSB first. They are described in Audio Data Formats, below. Refer to the

Electrical Characteristic section for timing information.

OUT+

OUT-

WM8972L

ROUT2INV = 1

SPKR

= OUT+ -(-OUT-) = (OUT+) + (OUT-)

-1

PLUS MIXER

MINUS MIXER

-OUTVOL

+OUTVOL

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