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7.1.11 SPECIFICATIONS FOR THE PROTECTION CIRCUITS FOR THE DIGITAL AMPLIFIER
The protection circuits for the Digital Amplifier are activated, following the specifications shown below. The error indication on
the FL display shows the reason a protection circuit was activated.
Upon diagnosis of the Digital Amplifier, refer to the specifications for the protection circuits here and the overview of the Digital
Amplifier circuitry.
1. Overview
The system microcomputer monitors the ports for shutdown requests (Pin 23:SD_AB and Pin 24: SD_CD) and the ports for
abnormal-temperature detection (Pin 25: /OTW) of the Power Stage ICs (IC3201, IC3301, and IC3401). As soon as any
abnormality is detected, it shuts the unit down.
To notify the user of the possibility of a too high a volume, when the unit is turned on the next time, the volume level will be set
to 0, and an error message will be displayed on the FL display.
2. Ports on the system microcomputer to be used for detection
Pin 77: SHUTDOWN
Low voltage at this pin means overcurrent or voltage too low (= V+B27) at a Power Stage IC.
Pin 79: XOTW
Low voltage at this pin means the temperature at the Power Stage ICs exceeded 125°C.
Note: As one Power Stage IC is provided with two channels, three Power Stage ICs (in total 6 channels) are mounted in
this unit. For abnormality detection, the unit implements a logical OR operation regarding these three ICs.
Therefore, which IC is abnormal cannot be known directly. To find which IC is abnormal, it ischeck the PWM
outputs (35, 38, 47, 50 pin) of the each power stage ICs (IC3201, IC3301, IC3401).
3. Detection timing
Start : Detection starts 500 ms after the PWRCONT 2 port (Pin 84) of the system microcomputer becomes active by your
pressing the STANDBY/ON key.
Finish : When the STANDBY/ON key is pressed again (when the power-off process starts).
4. Operation of the protection circuits
The following three protection circuits are activated when the conditions shown below are met:
Overcurrent detection: Indication on the FL display: OC ERROR
Conditions: If the SHUTDOWN ports, which are monitored every 10 ms, become low 7 out of 10 times. (If they become
low 7 times in succession, the conditions are met at that point.)
Abnormal temperature detection 1: Indication on the FL display: OVERTEMP
Conditions: If the XOTW ports, which are monitored every 10 ms, become low in succession for one minute.
Abnormal temperature detection 2: Indication on the FL display: OVERTEMP
(Prerequisite: The XOTW ports, which are monitored every 10 ms, become low three times in succession.)
Conditions: The above prerequisite is upheld, and the conditions for an overcurrent detection are met.
5. Process when the protection circuits are activated
The unit is shut down within 30 ms after abnormality detection then the volume level is set to 0. The unit can be turned on
immediately after the shutdown.
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