WM8987LGECOSLASHV datasheet(45/58 Pages) WOLFSON

45 / 58 page

Pre-Production

WM8987L

PP Rev 3.0 January 2007

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 43 ADC and DAC Oversampling Rate Selection

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

SAVING POWER AT HIGHER SUPPLY VOLTAGES

The analogue supplies to the WM8987L 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.

At lower voltages, performance can be improved by increasing the bias current. If low

power operation is preferred the bias current can be left at the default setting. 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: Highest bias current, optimized for

AVDD=1.8V

01: Bias current optimized for AVDD=2.5V

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

WM8987LGECO/V 数据表(PDF) 45 Page - Wolfson Microelectronics plc

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