User manual

TH-42PD25U 3.3V SOS detect
The Unregulated 15V and 1.8V lines are monitored for a voltage decrease. Under
normal conditions, the voltage drop derived from the voltage divider circuits at the base
of Q9714 or Q9716 is enough to turn the transistor on. However, should the voltage
drop decrease, either Q9716 or Q9714 turns off, allowing 5 volts at their collectors to
forward bias transistor Q9715. This effectively grounds pin 3 of the CPU IC9709 on the
D board, triggering the shutdown circuit.
Figure 29 - TH-42PD25U 3.3V SOS detect
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