WM8510GEDSSLASHV datasheet(28/56 Pages) WOLFSON

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WM8510

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PP Rev 1.2 December 2004

The digital audio data is converted to oversampled bit streams in the on-chip, true 24-bit digital

interpolation filters. The bitstream data enters a multi-bit, sigma-delta DAC, which converts it to a

high quality analogue audio signal. The multi-bit DAC architecture reduces high frequency noise and

sensitivity to clock jitter.

The DAC output defaults to non-inverted. Setting DACPOL will invert the DAC output phase on both

left and right channels.

AUTOMUTE

The DAC has an automute function which applied an analogue mute when 1024 consecutive zeros

are detected. The mute is release as soon as a non-zero sample is detected. Automute can be

disabled using the AMUTE control bit.

DAC OUTPUT LIMITER

The WM8510 has a digital output limiter function. The operation of this is shown in Figure 14. In this

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

the gain characteristic.

Figure 14 DAC Digital Limiter Operation

The limiter has a programmable upper threshold which is close to 0dB. Referring to Figure 14, 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.

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