IC DGTL AUDIO PWM PROC 64-TQFP

TAS5508APAG

Manufacturer Part NumberTAS5508APAG
DescriptionIC DGTL AUDIO PWM PROC 64-TQFP
ManufacturerTexas Instruments
TypePWM Processor
TAS5508APAG datasheet
 


Specifications of TAS5508APAG

ApplicationsDVDMounting TypeSurface Mount
Package / Case64-TQFP, 64-VQFPFor Use WithTAS5342DDV6EVM - TAS5342DDV6EVMTAS5508-5142K7EVM - EVAL MODULE FOR TAS5508B/TAS5142TAS5508-5122C6EVM - EVAL MODULE FOR TAS5508B/TAS5122TAS5508-5121K8EVM - EVAL MODULE FOR TAS5508B/TAS5121
Lead Free Status / RoHS StatusLead free / RoHS CompliantOther names296-17475
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TAS5508A
8-Channel Digital Audio PWM Processor
SLES119A – FEBRUARY 2004 – REVISED JULY 2009
Slopes k0, k1, and k2 define whether compression or expansion is to be performed within a given
region, and the degree of compression or expansion to be applied. Slopes are programmed as 28-bit
(5.23 format) numbers.
2.10.1 DRC Implementation
The three elements comprising the DRC include: (1) an rms estimator, (2) a compression/expansion
coefficient computation engine, and (3) an attack/decay controller.
RMS estimator—This DRC element derives an estimate of the rms value of the audio data stream into
the DRC. For the DRC block shared by Ch1 and Ch2, two estimates are computed—an estimate of the
Ch1 audio data stream into the DRC, and an estimate of the Ch2 audio data stream into the DRC. The
outputs of the two estimators are then compared, sample-by-sample, and the larger-valued sample is
forwarded to the compression/expansion coefficient computation engine.
Two programmable parameters, ae and (1 – ae), set the effective time window over which the rms
estimate is made. For the DRC block shared by Ch1 and Ch2, the programmable parameters apply to
both rms estimators. The time window over which the rms estimation is computed can be determined
by:
* 1
t
+
window
F
n(1 * ae)
S
Compression/expansion coefficient computation—This DRC element converts the output of the rms
estimator to a logarithmic number, determines the region where the input resides, and then computes
and outputs the appropriate coefficient to the attack/decay element. Seven programmable parameters,
T1, T2, O1, O2, k0, k1, and k2, define the three compression/expansion regions implemented by this
element.
Attack/decay control—This DRC element controls the transition time of changes in the coefficient
computed in the compression/expansion coefficient computation element. Four programmable
parameters define the operation of this element. Parameters ad and (1 – ad) set the decay or release
time constant to be used for volume boost (expansion). Parameters aa and (1 – aa) set the attack time
constant to be used for volume cuts. The transition time constants can be determined by:
* 1
t a +
F
n(1 * aa)
S
2.10.2 Compression/Expansion Coefficient Computation Engine Parameters
Seven programmable parameters are assigned to each DRC block: two threshold parameters—T1 and
T2, two offset parameters—O1 and O2, and three slope parameters—k0, k1, and k2. The threshold
parameters establish the three regions of the DRC transfer curve, the offsets anchor the transfer curve by
establishing known gain settings at the threshold levels, and the slope parameters define whether a given
region is a compression or an expansion region
The audio input stream into the DRC must pass through DRC-dedicated programmable input mixers.
These mixers are provided to scale the 32-bit input into the DRC to account for the positioning of the
audio data in the 48-bit DAP word and the net gain or attenuation in signal level between the SAP input
and the DRC. The selection of threshold values must take the gain (attenuation) of these mixers into
account. The DRC implementation examples that follow illustrate the effect these mixers have on
establishing the threshold settings.
T2 establishes the boundary between the high-volume region and the mid-volume region. T1 establishes
the boundary between the mid-volume region and the low-volume region. Both thresholds are set in
logarithmic space, and which region is active for any given rms estimator output sample is determined by
the logarithmic value of the sample.
36
Description
* 1
t
+
d
F
n(1 * ad)
S
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