Advanced Information
WM8753L
DEVICE DESCRIPTION
INTRODUCTION
The WM8753L is a low power audio codec combining a high quality stereo audio DAC with a high
quality stereo ADC and mono DAC. The stereo ADC may be configured for operation as a mono or
stereo voice ADC to operate with the mono DAC as a voice codec. Alternatively the ADC may be
configured as a hi-fi ADC for high quality record function. In voice mode the ADC filters are optimised
for voice record function. Applications for such a combined device include MP3 playing ‘smart-
phones’ and Bluetooth connected high quality stereo headsets. The mono voice codec might be used
either for the usual voice codec function, or perhaps as an additional codec for support of Bluetooth
links from such MP3 phones. Alternatively, if not required for such functions, the ADC of the codec
may be reconfigured so it is clocked off the I2S audio data interface domain, and its output sent over
the Hi-Fi audio interface as well as the voice audio interface, so it might be used as a recording ADC
in an I2S based audio system.
FEATURES
The chip offers great flexibility in use, and so can support many different modes of operation as
follows:
LINE INPUTS
The device includes two pairs of stereo analogue inputs that can be switched internally. LINE1 and
LINE2 can be used as either a pair of mono line level inputs, or as a single stereo pair. They may also
be used as differential input or be mixed together. A further two inputs, RXP and RXN, can be used
as a single differential input or mixed together. The output from these inputs can be played back in
stereo form to the headphones, or mono form to the transmit mono output. The mono output supports
both single ended and differential output, using a pair of output pins. If not required, the differential
output buffer may be powered down.
MICROPHONE INPUTS
Two microphone preamplifiers are provided, allowing for a pair of external microphones to be
differentially connected, with user defined gain using internal resistors, offering gain range from
+12dB to +30dB. Alternatively, three microphones can be connected to one microphone preamplifier,
with the second preamplifier disabled, and the microphone required is then selected. A microphone
bias is output from the chip which can be used to bias all microphones. The signal routing can be
configured to allow manual adjustment of mic levels, or indeed to allow the ALC loop to control the
level of mic signal that is transmitted.
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 analog/digital automatic level control (ALC) which keeps the recording
volume constant.
HI-FI DAC
The hi-fi DAC provides high quality audio playback suitable for all portable audio hi-fi type
applications, including MP3 players and portable disc players of all types.
VOICE CODEC
The on-chip stereo ADC and mono DAC are of a high quality using 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 codecs, up to the 48ks/s rate
used in high quality audio applications. The ADC digital filters may be switched for voice mode to
filters with steeper roll-off.
AI Rev 3.1 June 2004
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
