Sony AXS-R7 Service Manual page 19

• Input inverse-voltage protection of DC IN
When DC IN is an inverse voltage, the FET (Q205) on the DC-181 board does not work to prevent the inverse
voltage from being supplied to boards.
• Overcurrent protection of SW_UNREG
The input voltage SW_UNREG is protected by the overcurrent detection circuit (IC108) on the RE-340 board.
When a current larger than approx. 9 A flows in the SW_UNREG line, the SW_UNREG voltage is shut off. Since
the overcurrent detection circuit is not reset automatically even after the overcurrent is cleared, the unit must be
powered on again.
• Low-voltage protection and overvoltage protection of SW_UNREG
The input voltage SW_UNREG is protected by the low-voltage detection circuit and the overvoltage detection
circuit (IC101) on the RE-340 board.
Low-voltage protection circuit: SW_UNREG is turned on at approx. 8.7 V or more and is shut off at approx.
Overvoltage protection circuit: SW_UNREG is turned on at approx. 18.0 V or less and is shut off at approx. 18.9
V.
These circuits do not stop by latching when SW_UNREG is shut off and work automatically when normal voltage
is restored
Overcurrent protection of the DC OUT connector
The input voltage SW_UNREG can be supplied from the DC OUT connector to external devices.
The DC OUT line is protected by the overcurrent detection circuit (IC201). When a current larger than approx. 2.4 A
flows in the DC OUT line, the DC OUT line is shut off. Since power is not restored automatically even the overcurrent
is cleared, the unit must be powered on again.
Voltage conversion
The input voltage SW_UNREG is converted by the DC-DC converter to generate voltages +3.3 V_1, +3.3 V_4 (IC101),
+5.0 V, and +3.3 V_2 (IC102) in the DD-49 board and also generate a voltage of +2.5 V (IC201) in the RE-340 board.
Overcurrent protection in each power channel
If any voltage (+2.5 V, +3.3 V-1, +3.3 V-2, +3.3 V-3, +3.3 V-4, or +5.0 V) is shut off by overcurrent protection of each
DC-DC converter, only the DC-DC converter in which overcurrent was generated is deactivated.
Since power is not restored automatically even the overcurrent is cleared, the unit must be powered on again.
Power driving sequence
Since no power switch is provided in the unit, power is controlled from the camcorder. When power is turned on in the
camcorder, the POWER_GOOD signal is sent to the RE-340 board and the SW_UNREG signal is output. Then a voltage
of +3.3 V_DC is generated by the regulator and the RE-340 board controller CPLD (IC107) is activated.
Furthermore, the POWER_ON signal is sent to the RE-340 board. When the CPLD (IC107) on the RE-340 board senses
this signal, the DC-DC converter (IC101, IC102) on the DD-49 board and the DC-DC converter (IC201) on the RE-340
board are activated and these converters supply voltages +5.0 V, +3.3 V_1, +3.3 V_2, and +2.5 V to the DM-157 board.
When the DM-157 board can correctly generate power voltages for each IC from +5.0 V, +3.3 V_1, +3.3 V_2, and +2.5
V, the LP_PGOOD signal is sent to the FET (Q201) on the DD-49 board. The DC-DC converter IC103 generates +2.5
V and sends the Power Good signal to IC101. The FET (Q201) on the DD-49 board generates +3.3 V_3 from +3.3V_
2 generated by the DC-DC converter (IC102) and sends the RE_PGOOD signal to the CPLD (IC107) on the RE-340
board.
AXS-R7
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