Panasonic TDA-600 Service Manual page 36

KX-TDA600CE
voltage is supplied.
+3.3V is generated by the DC/DC converter is converted to +1.5V and supplied to IC200 core power.
BAT600, which is a lithium battery for memory backup, is connected to the power supply of IC621, IC622 (SRAM), IC411
(RTC)via D608, D609.
IC611 compares BAT600 output voltage to the reference voltage (about +2.7V) and drives LED (BATT ALARM) that
indicates dropping of backup voltage.
IP601 and IP602 block the line respectively when excess current flows to +15V and +3.3V line.
IP601 also functions as a voltage surge protector of +3.3V for the circuits Q610, D605 and so on.
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