WM8972LEFLSLASHR datasheet(37/49 Pages) WOLFSON

37 / 49 page

Preliminary Technical Data

WM8972L

PTD Rev 2.2 June 2004

SAVING POWER BY REDUCING OVERSAMPLING RATE

The default mode of operation of the ADC and DAC digital filters is in 128x oversampling mode.

Under the control of ADCOSR and DACOSR the oversampling rate may be halved. This will result in

a slight decrease in noise performance but will also reduce the power consumption of the device. In

USB mode ADCOSR must be set to 0, i.e. 128x oversampling.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

ADCOSR

ADC oversample rate select

1 = 64x (lowest power)

0 = 128x (best SNR)

R24 (18h)

Additional Control

(2)

DACOSR

DAC oversample rate select

1 = 64x (lowest power)

0 = 128x (best SNR)

Table 34 ADC and DAC Oversampling Rate Selection

ADCOSR set to ‘1’, 64x oversample mode, is not supported in USB mode (USB = 1).

SAVING POWER AT LOW SUPPLY VOLTAGES

The analogue supplies to the WM8972L can run from 1.8V to 3.6V. By default, all analogue circuitry

on the device 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

R23 (17h)

Additional

Control(1)

7:6

VSEL

[1:0]

Analogue Bias optimization

00: Lowest bias current, optimized for AVDD=1.8V

01: Low bias current, optimized for AVDD=2.5V

1X: Default bias current, optimized for AVDD=3.3V

Note:

In USB mode ADCOSR must be set to 0, i.e. 128x oversampling.

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