WM8986GECOSLASHV datasheet(33/87 Pages) WOLFSON

33 / 87 page

Pre-Production

WM8986

PP, Rev 3.1, February 2007

Note:

An additional gain of up to 12dB can be added using the gain block embedded in the

digital peak limiter circuit (see DAC OUTPUT LIMITER section).

5-BAND EQUALISER

A 5-band graphic equaliser function which can be used to change the output frequency levels to suit

the environment. This is described in the 5-BAND EQUALISER section.

3-D ENHANCEMENT

The WM8986 has an advanced digital 3-D enhancement feature which can be used to vary the

perceived stereo separation of the left and right channels.

Refer to the 3-D STEREO

ENHANCEMENT section for further details on this feature.

DAC DIGITAL OUTPUT LIMITER

The WM8986 has a digital output limiter function. The operation of this is shown in Figure 20. In this

diagram the upper graph shows the envelope of the input/output signals and the lower graph shows

the gain characteristic.

Figure 20 DAC Digital Limiter Operation

The limiter has a programmable upper threshold which is close to 0dB. Referring to Figure 20, in

normal operation (LIMBOOST=000 => limit only) signals below this threshold are unaffected by the

limiter. Signals above the upper threshold are attenuated at a specific attack rate (set by the

LIMATK register bits) until the signal falls below the threshold. The limiter also has a lower threshold

1dB below the upper threshold. When the signal falls below the lower threshold the signal is

amplified at a specific decay rate (controlled by LIMDCY register bits) until a gain of 0dB is reached.

Both threshold levels are controlled by the LIMLVL register bits. The upper threshold is 0.5dB above

the value programmed by LIMLVL and the lower threshold is 0.5dB below the LIMLVL value.

VOLUME BOOST

The limiter has programmable upper gain which boosts signals below the threshold to compress the

dynamic range of the signal and increase its perceived loudness. This operates as an ALC function

with limited boost capability. The volume boost is from 0dB to +12dB in 1dB steps, controlled by the

LIMBOOST register bits.

The output limiter volume boost can also be used as a stand alone digital gain boost when the limiter

is disabled.

WM8986GECO/V Datasheet(PDF) 33 Page - Wolfson Microelectronics plc