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10.5. POWER SUPPLY CIRCUIT
This circuit converts the voltage supplied from PBX into the power supply voltage of +3.3V by
IC1 (Switching Regulator IC).
Q22 and Q23 control the power supply circuit as below to turn IC1 on in low consumption
current at starting up.
- Input Voltage approx. 26V or less
3 H
IC1 OFF
- Input Voltage approx. 26V or more
Q23 OFF
Q23 ON
17
Q22 ON
IC1-pin
Q22 OFF
IC1 ON
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