WM8948ECSSLASHR datasheet(23/189 Pages) WOLFSON

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WM8948

PD, May 2011, Rev 4.1

DEVICE DESCRIPTION

INTRODUCTION

The WM8948 is a highly integrated low power hi-fi CODEC designed for portable devices such as

digital still cameras and multimedia phones. Flexible analogue interfaces and powerful digital signal

processing (DSP) in a 2.96 x 3.06mm footprint make it ideal for small portable devices.

The WM8948 supports up to 6 analogue audio inputs. One pair of single-ended or pseudo differential

microphone / line inputs is selected as the ADC input source. The two auxiliary inputs can be

selected as line inputs to the ADC, or as direct signal paths to the output mixers. An integrated bias

reference is provided to power standard electret microphones. A two-channel digital microphone

interface is also supported, with direct input to the DSP core via the ADCs.

The stereo hi-fi ADCs and DACs operate at sample rates from 8kHz up to 48kHz. A high pass filter is

available in the ADC path for removing DC offsets and suppressing low frequency noise such as

mechanical vibration and wind noise. A digital tone (‘beep’) generator allows audio tones to be

injected into the DAC output path.

The WM8948 provides a powerful DSP capability for configurable filtering and processing of the

digital audio paths. The DSP provides low-pass / high-pass filtering, 3D stereo enhancement, notch

filters, 5-band EQ, dynamic range control and a programmable DF1 digital filter. The tuned notch

filters allow narrow frequency bands to be attenuated, to provide filtering of motor noise or other

unwanted sounds; the 5-band EQ allows the signal to be adjusted for user-preferences. The dynamic

range control provides a range of compression, limiting and noise gate functions to support optimum

configuration for recording or playback modes. The DF1 filter allows user-specified algorithms to be

implemented in the digital signal chain.

The Wolfson ReTune™ feature is a highly-configurable DSP algorithm which can be tailored to

cancel or compensate for imperfect characteristics of the housing, loudspeaker or microphone

components in the target application. The ReTune™ algorithm coefficients and register contents are

calculated using Wolfson’s WISCE™ software; lab bench tests and audio reference measurements

must be performed in order to determine the optimum settings.

The digital signal routing between the ADCs, DACs and I2S digital audio interface can be configured

in different ways according to the application requirements. The DSP functions may be applied to the

ADC record path, or the DAC playback path.

Four analogue output mixers are provided, connected to 4 analogue output pins. Twin stereo outputs

or stereo line and mono BTL headphone/speaker may be connected to these outputs.

The WM8948 incorporates an LDO regulator for compatibility with a wide range of supply rails; the

internal LDO can also reduce any interference resulting from a noisy supply rail. The LDO regulator

can also be used to provide a regulated supply voltage to other circuits.

I2C or SPI control interface modes for read/write access to the register map. A single external clock

provides timing reference for all the digital functions; an integrated Frequency Locked Loop (FLL)

also provides flexibility to perform frequency conversions and to remove noise/jitter from the external

clock. The FLL can be configured for reduced power consumption, or for different filtering

requirements of the reference source.

Additional functions include a 4-wire controller for interface to standard resistive touch panels, a 12-

bit auxiliary ADC for DC measurement / battery monitoring, and also a current-mode video buffer

providing excellent video signal reproduction at low operating voltages. Up to 4 GPIO pins may be

configured for miscellaneous input/output, or for status indications from the Touch panel, AUXADC or

temperature monitoring functions.

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