WM9711 datasheet(45/66 Pages) WOLFSON

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Production Data

WM9711L

PD Rev 4.1 April 2004

LOW POWER STANDBY MODE

If all the bits in registers 26h and 24h are set, then the WM9711L is in low-power standby mode and

consumes very little current. A 1M

Ω resistor string remains connected across AVDD to generate

VREF. This is necessary if the on-chip analogue comparators are used (see “Battery Alarm” section),

and helps shorten the delay between wake-up and playback readiness. If VREF is not required, the

Ω resistor string can be disabled by setting the SVD bit, reducing current consumption further.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

58h

SVD

VREF Disable

0: VREF enabled using 1M

Ω string (low-power

standby mode)

1 : VREF disabled, 1M

Ω string disconnected

(OFF mode)

Table 33 Disabling VREF (for lowest possible power consumption)

SAVING POWER AT LOW SUPPLY VOLTAGES

The analogue supplies to the WM9711L can run from 1.8V to 3.6V. By default, all analogue circuitry

on the IC is optimized to run at 3.3V. This set-up is also good for all other supply voltages down to

1.8V. However, at lower voltages, it is possible to save power by reducing the internal bias currents

used in the analogue circuitry. This is controlled as shown below.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

5Ch

6:5

V[1:0]

Analogue Bias optimization

11 : Lowest bias current, optimized for 1.8V

10 : Low bias current, optimized for 2.5V

01, 00 : Default bias current, optimized for 3.3V

Table 34 Analogue Bias Selection

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