Specifications For The Protection Circuits For The Digital Amplifier - Pioneer SX-LX70SW Service Manual

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5.6 SPECIFICATIONS FOR THE PROTECTION CIRCUITS FOR THE DIGITAL AMPLIFIER

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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 3: /SD) and the ports for abnormal-temperature
detection (Pin 2 : /OTW) of the Power Stage ICs (IC3201, IC3301, IC3401 and IC3501). 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.
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2. Ports on the system microcomputer to be used for detection
Pin 77: SHUTDOWN
Low voltage at this pin means overcurrent at the Power Stage ICs or that the power supply voltage for the gate
drive for the Power Stage ICs (= GVDD, Pins 1, 18, 19 and 36), i.e., VG+12 is less than 10V.
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, four Power Stage ICs (in total 8 channels) are mounted in
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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 is required to check
whether abnormally detection is activated or not with the abnormality detection port of each IC open (by
temporarily removing a series resistor (IC3201: R3201, R3202, IC3301: R3301, R3302, IC3401: R3401, R3402,
IC3501: R3501, R3502)).
3. Detection timing
Start : Detection starts 500 ms after the PWRCONT port (Pin 78) of the system microcomputer becomes active by your
pressing the STANDBY/ON key.
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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 1: Indication on the FL display: OC ERROR1
Conditions: If the SHUTDOWN ports, which are monitored every 10 ms, become low 7 times in succession.
Overcurrent detection 2: Indication on the FL display: OC ERROR2
Conditions: At the P.CONFIG port (Pin21), which are monitored every 30 ms, 5.2A (ucom threshold 153) is fixed at
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3000/6000 (MIN 180 sec/ MAX 270 sec).
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
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immediately after the shutdown.
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