WM8972LEFLSLASHR datasheet(27/49 Pages) WOLFSON

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Preliminary Technical Data

WM8972L

PTD Rev 2.2 June 2004

OUT2 OUTPUT

The OUT2 pin can drive a 16

Ω or 32Ω headphone or a line output or be used as a DC reference for a

headphone output (see Headphone Output section). It can be selected to either drive out an inverted

OUT- or inverted MONOOUT for e.g. a differential output between OUT2 and MONOOUT.

OUT2SW selects the mode of operation required.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R24 (18h)

Additional

Control (2)

8:7

OUT2SW

[1:0]

OUT2 select

00 : VREF

01 : RESERVED (Do not use)

10 : MONOOUT

11 : minus mixer output (no volume

control through -OUTVOL)

Table 20 OUT2 Select

ENABLING THE OUTPUTS

Each analogue output of the WM8972L can be separately enabled or disabled. The analogue mixer

associated with each output is powered on or off along with the output pin. All outputs are disabled by

default. To save power, unused outputs should remain disabled.

Outputs can be enabled at any time, except when VREF is disabled (VR=0), as this may cause pop

noise (see “Power Management” and “Applications Information” sections)

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

OUT+

OUT+ Enable

OUT-

OUT- Enable

MONO

MONOOUT Enable

R26 (1Ah)

Power

Management

(2)

OUT2

OUT2 Enable

Table 21 Analogue Output Control

Whenever an analogue output is disabled, it remains connected to VREF (pin 20) through a resistor.

This helps to prevent pop noise when the output is re-enabled. The resistance between VREF and

each output can be controlled using the VROI bit in register 27. The default is low (1.5k

Ω), so that

any capacitors on the outputs can charge up quickly at start-up. If a high impedance is desired for

disabled outputs, VROI can then be set to 1, increasing the resistance to about 40k

Ω.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R27 (1Bh)

Additional (1)

VROI

VREF to analogue output resistance

0: 1.5 k

Ω

1: 40 k

Ω

Table 22 Disabled Outputs to VREF Resistance

THERMAL SHUTDOWN

The speaker output can drive very large currents. To protect the WM8972L from overheating a

thermal shutdown circuit is included. If the device temperature reaches approximately 150

0C and the

thermal shutdown circuit is enabled (TSDEN = 1 ) then the speaker outputs will be disabled.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R23 (17h)

Additional

Control (1)

TSDEN

Thermal Shutdown Enable

0 : thermal shutdown disabled

1 : thermal shutdown enabled

Table 23 Thermal Shutdown

WM8972LEFL/R 数据表(PDF) 27 Page - Wolfson Microelectronics plc

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