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5.4 PROTECTION CIRCUIT
(1) DIGITAL AMP Part
Overview
Sound AMP IC (IC5501) has following functions:
1. PLL abnormal oscillatory
2. Abnormality of MDSP processing
3. Excess of the amount of SDSP processing
4. Protection from overcurrent
5. Protection from abnormally high temperature
6. DC detection
7. Abnormality of DAIF clock
W
hen abnormality is detected, SP and AMP are protected by stopping processing, muting, stopping output of AMP.
In addition, pin 22 is made "L" against above-mentioned 1 to 6 abnormality.
W
hen microcomputer detects abnormality of AMP, microcomputer initializes and reboots AMP.
Ports on the system microcomputer to be used for detection
• Pin 49 of IC3001 P4_3
This terminal becomes "L", which detects the fact that errors occurred at SoundAMP.
• Regarding Abnormality of DAIF clock, ports detect by reading out register of error information by communicating with
Sound
AMP.
Operation of the protection circuits
1. PLL abnormal oscillatory
Mute in digital amplifier is set. (AMP IC set automatically.)
Pin 22 of Sound AMP IC (IC5501) becomes "L".
2. Abnormality of MDSP processing
3. Excess of the amount of SDSP processing
MDSP and SDSP processing are stopped and MUTE in Digital Amplifier is set. (AMP IC set automatically.)
Pin 22 of Sound AMP IC (IC5501) becomes "L".
4. Protection from overcurrent
A short circuit of Digital Amplifier output terminal between
V
SS,
V
DD, and +/- is detected.
All output by Digital Amplifier will be stopped (AMP IC set automatically.)
Pin 22 of Sound AMP IC (IC5501) becomes "L".
5. Protection from abnormally high temperature
MDSP and SDSP processing are stopped and MUTE in Digital Amplifier is set. Also, output by all Digital Amplifier will be
stopped. (AMP IC set automatically.)
Pin 22 of Sound AMP IC (IC5501) becomes "L".
6. DC detection
W
hen the DC voltage is output for more than 1.5 seconds continuously, output by digital amplifier will be stopped.
(AMP IC set automatically.)
Pin 22 of Sound AMP IC (IC5501) becomes "L".
Digital Amplifier outputs with no signal. (AMP IC set automatically)
This error can be detected by reading register out.
when protection circuit is detected
SoundAMP is reseted and initialization is done.
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