SAF7849HL/M295,557 NXP Semiconductors, SAF7849HL/M295,557 Datasheet - Page 13

• Manufacturer Part Number: SAF7849HL/M295,557
• Description: IC AUD DECODER 144LQFP
• Manufacturer: NXP Semiconductors
• Type: Audio Decoderr

Specifications of SAF7849HL/M295,557

• Applications: Audio CD
• Voltage - Supply, Analog: 3 V ~ 3.6 V
• Voltage - Supply, Digital: 1.8V, 3.3V
• Mounting Type: Surface Mount
• Package / Case: 144-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 935287932557

NXP Semiconductors
SAF784X_2
Product data sheet
6.3 General purpose analog inputs
6.4 Auxiliary analog inputs
that can decrease the quality of audio. The clocks related to audio DAC and LF ADC are
generated directly from the analog signal, instead of being derived from high frequency
PLLs. The clocking strategy for the digital core is shown in
The four general purpose ADC inputs, GPIO0 (pin 33), GPIO1 (pin 34), GPIO2 (pin 35),
and GPIO3 (pin 36), can be used for giving the ARM microprocessor access to external
analog sources, such as monitoring temperature and to provide simple resistor-ladder
keypad functionality. These inputs use an additional pair of sigma-delta ADCs identical to
those used for the LF diode inputs.
The general purpose analog inputs have separate interrupt request lines and use address
space in the servo registers for storing the converted digital values. The output of the
general purpose ADCs are low-pass filtered and can have fine-offset compensation
added before being passed to a decimation filter. The digital values output from the
decimation filter are then captured in the servo registers with a resolution of 10 bits per
channel.
There are only two ADCs for general purpose application and so each ADC is multiplexed
between two inputs: ADC1 between GPIO0 and GPIO2, and ADC2 between GPIO1 and
GPIO3. GPIO2 and GPIO3 inputs are selected by signal AuxControlandGPADC.
Analog inputs, AUX_L and AUX_R, are available, and have sufficient resolution, for the
input of external audio sources, such as allowing ARM access to an external audio source
for sound processing algorithms. This allows audio processing of external audio sources
via the AUX pins, whilst simultaneously using the general purpose inputs for keyboard and
temperature inputs.
Since these two inputs share one pair of the LF sigma-delta ADCs used in the LF path (for
inputs D1 and D2) a multiplexer is used to control the data source into the ADCs.
Therefore, D1 and D2 cannot be used at the same time as AUX_L and AUX_R. This path
is designed for a tuner input where the THD specification is ~0.3 % and the S/N is
< 60 dB. These performance values are lower than when the normal CD audio path is
used i.e. S/N > 80 dB and THD < 0.01 %.
The audio data is converted to a pulse-density modulated digital stream for both input
channels. This data is then low-pass filtered and decimated to produce 10-bit
representations of the analog inputs.
The auxiliary inputs differ from the general purpose analog inputs because the parallel
data is converted to an I
the data available to the ARM microprocessor. The I
FIFO which allows the ARM microprocessor to service the audio data with a lower priority
than it would need if it were directly registered; see
One chip CD audio device with integrated MP3/WMA decoder
2
Rev. 02 — 9 May 2008
S format stream and then sent to the I
Figure
2
S handler contains a 12-deep data
6.
Figure
2
S handler block to make
9.
SAF784x
© NXP B.V. 2008. All rights reserved.
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