SAF7849HL/M295,557 NXP Semiconductors, SAF7849HL/M295,557 Datasheet - Page 51

• 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
6.6.2 Diode signal processing
The SAF784x contains additional circuits to implement a servo feature called Flexi servo.
The purpose of the flexible servo system is, in conjunction with the existing analog and
digital LF path, to provide maximum flexibility in the use of the entire servo loop. This
scheme extends from the point of diode PDM generation at the analog ADC outputs
through to the servo actuator signals (RA, FO and SL) themselves.
From a system perspective, the simplest configuration provides an LF path that is
equivalent to the hardware servo (PDSIC) of the other audio devices such as SAA7826,
which uses the on-board hardware servo controller logic. However, an alternative setup
will provide additional fine DC-offset compensation (in addition to the coarse
compensation already found in the analog ADCs) and the potential for full software servo
control via the ARM microprocessor. Full system configuration details are given in the
block diagrams in the sections below.
The photo detector in conventional two-stage three-beam compact disc systems normally
contains six discrete diodes. Four of these diodes (three for single foucault systems) carry
the Central Aperture signal (CA) while the other two diodes (satellite diodes) carry the
radial tracking information. The CA signals are summed into an HF signal for the decoder
function and are also differenced (after A-D conversion) to produce the low frequency
focus control signals.
The low frequency content of the six (five if single Foucault) photodiode inputs are
converted to pulse-density modulated bit streams by a multiplexed 6-bit ADC followed by a
digital PDM generation circuit. This supports a range of OPUs in Voltage mode
mechanisms by having sixteen selectable gain ranges in two sets, one set for D1 to D4
and the other for R1 and R2.
Fig 28. Function of servo IRQ signal with respect to srv_fc0, srv_fc1 and inreq_clr
inreq_clr
srv_fc0
srv_fc1
IRQ
natural duration of
IRQ cycle time of ~60 s
IRQ (~45 s)
One chip CD audio device with integrated MP3/WMA decoder
Rev. 02 — 9 May 2008
int #1
cleared by
inreq_clr
IRQ #2
int #2
pulse
IRQ cycle time of ~60 s
cleared by
IRQ cycle time of ~60 s
inreq_clr
IRQ #3
int #3
pulse
SAF784x
© NXP B.V. 2008. All rights reserved.
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