Read Panasonic KX-UT248RU / KX-UT248RU-B (serv.man3) Service Manual online
17
KX-UT248RU/KX-UT248RU-B
4.2.9.1.
12V/9V
→ 3.3V
This Power circuit is DCDC step-down convertor cuircuit that outputs 3.3V from input voltage(12V(PoE)/9V(AC adaptor).
IC304 starts operating when the voltage at pin1 becomes 1.5V or more. And IC304 controls Q301 so that the voltage divided by
R304 and R319 may become 1V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 3.3V.
IC304 starts operating when the voltage at pin1 becomes 1.5V or more. And IC304 controls Q301 so that the voltage divided by
R304 and R319 may become 1V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 3.3V.
4.2.9.2.
12V/9V
→ 5V
This Power circuit is DCDC step-down convertor cuircuit that outputs 5.0V from input voltage(12V(PoE)/9V(AC adaptor).
IC302 starts operating when the voltage at pin1 becomes 1.6V or more. And IC302 controls the transistor built into IC302 so that
the voltage divided by R303 and R306 may become 0.8V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 5.0V.
IC302 starts operating when the voltage at pin1 becomes 1.6V or more. And IC302 controls the transistor built into IC302 so that
the voltage divided by R303 and R306 may become 0.8V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 5.0V.
4.2.9.3.
12V/9V
→ 24V
This Power circuit is DCDC step-up convertor cuircuit that outputs 24V from input voltage(12V(PoE)/9V(AC adaptor).
IC305 starts operating when the voltage at pin1 becomes 1.8V or more. And IC305 controls the transistor built into IC305 so that
the voltage divided by R321,R322 and R323 may become 0.2V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 24V.
IC305 starts operating when the voltage at pin1 becomes 1.8V or more. And IC305 controls the transistor built into IC305 so that
the voltage divided by R321,R322 and R323 may become 0.2V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 24V.
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