Circuit Description Of Digital Amp. Section - Pioneer SX-LX70SW Service Manual

5

5.5 CIRCUIT DESCRIPTION OF DIGITAL AMP. SECTION

TAS5508BPAG
Filter
PCM Signal and
Volume
From
DSP
IC3101
PWM Processor section
PWM Processor section
The PCM signals output from the DSP are input to this section, and their volume and sound quality are digitally adjusted.
At the output stage, after conversion from PCM to PWM, the signals are output to the Power stage.
Power Stage section
In this section, timing is controlled so that the MOSFETs on the high and low sides will not be turned on simultaneously. The
voltage of the PWM signals are raised to drive the gates of the MOSFET, and the PWM signals to drive the speakers are
output from the MOSFET at the output stage. Detection and protection functions against short-circuiting of the output
signals and temperature exceeding the standard value are also provided.
If the detection and protection work, the ports of the power stage ICs become the following state.
Output LPF section
The carrier elements, high-frequency signals that are unnecessary for these speakers, are eliminated. The signals passed
through the LPF will become sine-wave signals, as shown in the figure above.
5
6
To UCOM
XSD
XOTW
PCM -> PWM
Protection
*1 XSD
*2 XOTW : OTW (2pin)
Power Stage ICs No.
IC3201
IC3301
IC3401
IC3501
SX-LX70SW
6
7
3.3V
0V
*1
*2
TAS5142DKD
Gate
Drive
Timing
Control
Gate
Drive
IC3201, IC3301, IC3401, IC3501
: SD (3pin)
Power Stage section
Protection Enable State
SD (3pin) => L
OTW (2pin) => L
7
8
30.5V
0V 0V
0V
Output LPF section
45
8
A
B
C
D
E
F