WM8952ECSSLASHRV datasheet(15/72 Pages) WOLFSON

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WM8952

PP, Rev 3.1, June 2011

DEVICE DESCRIPTION

INTRODUCTION

FEATURES

The WM8952 is a low power audio ADC, with flexible line and microphone input. It offers great

flexibility in use, and so can support many different modes of operation as follows:

MICROPHONE INPUTS

Two microphone inputs are provided, allowing for either a differential microphone input or a single

ended microphone to be connected. These inputs have a user programmable gain range of -12dB

to +35.25dB using internal resistors. After the input PGA stage comes a boost stage which can add

a further 20dB of gain. A microphone bias is output from the chip which can be used to bias the

microphones. The signal routing can be configured to allow manual adjustment of mic levels, or to

allow the ALC loop to control the level of mic signal that is transmitted.

Total gain through the microphone paths of up to +55.25dB can be selected.

PGA AND ALC OPERATION

A programmable gain amplifier is provided in the input path to the ADC. This may be used manually

or in conjunction with a mixed analogue/digital automatic level control (ALC) which keeps the

recording volume constant.

AUX INPUT

The device includes a mono input, AUX, which can also be mixed into the signal path in a flexible

fashion, either to the input PGA as a second microphone input or as a line input. The configuration

of this circuit, with integrated on-chip resistors allows several analogue signals to be summed into

the single AUX input if required.

ADC

The mono ADC uses a multi-bit high-order oversampling architecture to deliver optimum

performance with low power consumption. Various sample rates are supported, from the 8ks/s rate

typically used in voice dictation, up to the 48ks/s rate used in high quality audio applications.

DIGITAL FILTERING

Advanced Sigma Delta Converters are used along with digital decimation and interpolation filters to

give high quality audio at sample rates from 8ks/s to 48ks/s.

Application specific digital filters are also available which help to reduce the effect of specific noise

sources such as wind noise or narrowband noise from other parts of the system. The filters include a

programmable ADC high pass filter and four fully programmable ADC notch filters.

AUDIO INTERFACES

The WM8952 has a standard audio interface, to support the transmission of audio data to and from

the chip. This interface is a 4 wire standard audio interface which supports a number of audio data

formats including I2S, DSP Mode, MSB-First, left justified and MSB-First, right justified, and can

operate in master or slave modes.

CONTROL INTERFACES

To allow full software control over all its features, the WM8952 supports 2 or 3 wire control interface.

It is fully compatible and an ideal partner for a wide range of industry standard microprocessors,

controllers and DSPs. The selection between 2-wire mode and 3-wire mode is determined by the

state of the MODE / GPIO pin. If MODE / GPIO is high then 3-wire control mode is selected, if

MODE is low then 2-wire control mode is selected.

In 2 wire mode, only slave operation is supported, and the address of the device is fixed as 0011010.

CLOCKING SCHEMES

WM8952 supports the normal audio clocking scheme operation, where 256fs MCLK is provided to

the ADC.

However, a PLL is also included which may be used to generate the internal master clock frequency

in the event that this is not available from the system controller. This PLL uses an input clock,

typically the 12MHz USB or ilink clock, to generate high quality audio clocks. If this PLL is not

required for generation of these clocks, it can be reconfigured to generate alternative clocks which

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