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WM8733

WOLFSON MICROELECTRONICS LTD

PP Rev 1.3 July 2000

5

DEVICE DESCRIPTION

INTRODUCTION

WM8733 is a complete high performance stereo audio 18-bit digital-to-analogue converter, including

digital interpolation filter, multibit sigma-delta with dither, and switched capacitor multibit stereo DAC

and output smoothing filters.

Special functions of soft mute and de-emphasis are provided, and operation using system clock of

256fs, or 384fs or 512fs is provided, selection between either clock rate being automatically

controlled. Sample rates (fs) from less than 8ks/s to 96ks/s are allowed, provided the appropriate

system clock is input.

An auto mute function is provided which is enabled if MUTE (pin 10) is left at high impedance. If 64

successive left and right channel data samples of value 0 are received, auto mute is achieved. This

signal is wire ORed to MUTE (pin 10) via 10K resistor. If MUTE (pin 10) internally is not externally

driven, the internal auto mute state is visible on this pin as a weak drive strength signal (10k

Ω

source).

MUTE

DESCRIPTION

0

Z

1

Soft mute is OFF

Auto mute is enabled

Soft mute is ON

Table 1 Soft Mute Control

A novel multi bit sigma-delta DAC design is used, utilising a 64x oversampling rate, to optimise

signal to noise performance and offer increased clock jitter tolerance.

Internally generated midrail references are used to DC bias output signals, requiring only a single

external capacitor for decoupling purposes.

The device is packaged in a small 14-pin SOIC package, offering pin compatibility with Burr Brown

PCM1733, but with added functionality of a soft mute input pin, which may be left floating to enable

auto mute detection, or held ‘low’ leaving the device operational.

Single 3V to 5V supplies may be used, the output amplitude scaling with absolute supply level. Low

supply voltage operation and low current consumption, and the low pin count small package, make

the WM8733 attractive for many consumer type applications.