wm8952 Wolfson Microelectronics plc, wm8952 Datasheet - Page 14

• Manufacturer Part Number: wm8952
• Description: Mono Adc With Microphone Pre-amplifier
• Manufacturer: Wolfson Microelectronics plc

WM8952
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DEVICE DESCRIPTION
INTRODUCTION
AUX INPUT
DIGITAL FILTERING
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.
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.
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 I
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
may then be output on the GPIO pin and used elsewhere in the system.
2
S, DSP Mode, MSB-First, left justified and MSB-First, right justified, and can
PP, Rev 3.0, December 2008
Pre Production
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