WM8976CGEFLSLASHV datasheet(21/114 Pages) WOLFSON

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Production Data

WM8976

PD, Rev 4.5, November 2011

Alternatively, if a speaker output is not required, the LOUT2 and ROUT2 pins might be used as a

stereo headphone driver, (disable output invert buffer on ROUT2). In that case two sets of

headphones might be driven, or the LOUT2 and ROUT2 pins used as a line output driver.

OUT3 and OUT4 can be configured to provide an additional stereo lineout from the output of the

DACs, the mixers or the input microphone boost stages. Alternatively OUT4 can be configured as a

mono mix of left and right DACs or mixers, or simply a buffered version of the chip midrail reference

voltage. OUT3 can also be configured as a buffered VMID output. This voltage may then be used as

a headphone ‘pseudo ground’ allowing removal of the large AC coupling capacitors often used in the

output path.

AUDIO INTERFACES

The WM8976 has a standard audio interface, to support the transmission of data to and from the chip.

This interface is a 3 wire standard audio interface which supports a number of audio data formats

including I2S, DSP/PCM Mode (a burst mode in which LRC sync plus 2 data packed words are

transmitted), 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 features, the WM8976 offers a choice of 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.

Selection between the modes is via the MODE pin. In 2 wire mode the address of the device is fixed

as 0011010.

CLOCKING SCHEMES

WM8976 offers the normal audio DAC clocking scheme operation, where 256fs MCLK is provided to

the DAC and ADC.

A PLL is included which may be used to generate these clocks in the event that they are 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 pins and used

elsewhere in the system.

POWER CONTROL

The design of the WM8976 has given much attention to power consumption without compromising

performance. It operates at very low voltages, and includes the ability to power off any unused parts

of the circuitry under software control, and includes standby and power off modes.

OPERATION SCENARIOS

Flexibility in the design of the WM8976 allows for a wide range of operational scenarios, some of

which are proposed below:

Multimedia phone; High quality playback to a stereo headset, a mono ear speaker or a loudspeaker is

supported, allowing hi-fi playback to be mixed with voice and other analogue inputs while

simultaneously transmitting a differential output from the microphone amplifier. A 5-band EQ enables

hi-fi playback to be customised to suit the user's preferences and the music style, while

programmable filtering allows fixed-frequency noise (e.g. 217Hz) to be reduced in the digital domain.

Camcorder; the provision of a microphone preamplifier allows support for both internal and external

microphones. All drivers for speaker, headphone and line output connections are integrated. The

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