WM8945ECSSLASHR datasheet(22/169 Pages) WOLFSON

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WM8945

Production Data

PD, May 2011, Rev 4.1

DEVICE DESCRIPTION

INTRODUCTION

The WM8945 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 WM8945 supports up to 4 analogue audio inputs. One single-ended or pseudo differential

microphone / line input 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 digital microphone interface is also supported,

with direct input to the DSP core via the ADC.

The hi-fi ADC and DAC 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 WM8945 provides a powerful DSP capability for configurable filtering and processing of the

digital audio path. The DSP provides low-pass / high-pass filtering, 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 ADC, DAC 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.

Three analogue output mixers are provided, connected to 3 analogue output pins. A mono line output

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

The WM8945 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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