D2-45057_14 Datasheet, PDF (27/31 Pages) Intersil Corporation – Intelligent Digital Amplifier PWM Controller and Audio Processor

D2-45057, D2-45157
Graceful Overcurrent and Short Circuit
Hard faults from overcurrent or short circuit conditions
shut down the outputs. High-threshold over-temperature
also causes a shut down. For lower-threshold event
detections, graceful protection is provided for each
output. Specific operation depends on type and severity
of the detected event, but action taken is to reduce
conditions that would contribute to the event, without
the severity of a complete shut-down as in a high-limit
fault condition.
Overcurrent monitoring status is presented to the
PROTECT0-2 inputs, from per-output detector status that
drives the nERROR0-3 outputs. Overcurrent detection
algorithms in firmware monitor these peak level
detections, and upon detection of an overload condition,
automatically reduce PWM gain. This Automatic Gain
Control (AGC) action aids to prevent clipping of audio
output, as well as avoiding related excessive-level
conditions. The AGC algorithm operation functions
through a stepped-changing of PWM gain reduction,
corresponding to characteristics and time-event
detection of overloads. At the lower (non shut-down)
high-temperature threshold, the AGC function also acts to
attenuate the outputs to attempt to reduce temperature.
Output level gain and level change effects from this AGC
function are similar to operation from a compressor.
However, unlike a compressor where characteristics are
determined by input levels, the PWM AGC operation is
controlled through detection of near-overload output
levels or from high temperature detection.
Power Supply Voltage Monitoring
Undervoltage sensors and brownout detectors monitor all
supply voltages to the device. The logic and built-in
protection of this voltage monitoring prevents operation
until all supply voltages are within their specified limits.
Also, if any of these monitored voltages drop below their
threshold, the device shuts down its outputs and asserts
all four of the nERROR outputs.
Audio Processing
The audio processing, signal flow, and system definition
is defined by the D2-45057, D2-45157 device internal
ROM firmware, and executed by the DSP. This firmware
defines the audio flow architecture, which includes the
audio processing blocks. Each of these blocks are
programmable, allowing for adjustment of their
audio-controlling parameters. The signal flow and audio
processing blocks are shown in Figure 17. This
architecture includes audio processing functions of:
• Input Selection
• Mixers
• Input Compressors and Output Limiters
• Tone Controls
• 5-Band and 3-Band Parametric Equalizers
• Router
• High/Low-Pass Crossover Filters
• Volume and Output Level Controls
• Loudness Contour
Enhancement audio processing is also used. Depending
on which device, (D2-45057 or D2-45157) either the
D2Audio SoundSuite™ or SRS WOW/HD™ algorithms
are included.
Audio Processing Signal Flow Blocks
INPUT SELECTION
The Input Select register specifies the audio inputs that
are assigned to the audio processing input path. Either
the I²S or S/PDIF Digital inputs are available.
MIXERS
An input mixer provides a two-input, two-output mixing
and routing path. Either input can be mixed at adjustable
gain into either or both of the two outputs. Default
setting is 0 dB through each channel, with full cut-off for
non-through channels. Attenuation is continuously
variable with the programmable parameters.
A stereo mixer provides a path from the two input
channels. This typically is used to provide a mix of both
stereo input channels for crossover processing and
becoming the source for the subwoofer channel. Gains
for both input channels are adjustable to feed the single
stereo mixer output.
TONE CONTROLS
A tone control block is included in both of the two input
channels. Each of the filters (bass or treble) is
implemented with a first-order (6dB/octave) roll-off,
using programmable corner frequency and a boost or
attenuating gain. The signal flow processing
automatically provides a smooth transition between tone
control changes.
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FN6785.0
July 29, 2010