Read Panasonic KX-UT248RU / KX-UT248RU-B (serv.man3) Service Manual online
18
KX-UT248RU/KX-UT248RU-B
4.2.9.4.
3.3V
→ 1.2V
This Power circuit is DCDC step-down convertor cuircuit that outputs 1.2V from input voltage 3.3V.
IC301 starts operating when the voltage at pin1 becomes 1.2V or more. And IC301 controls Q302 so that the voltage divided by
R317 and R327 may become 0.9V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 1.2V.
IC301 starts operating when the voltage at pin1 becomes 1.2V or more. And IC301 controls Q302 so that the voltage divided by
R317 and R327 may become 0.9V, and adjusts the output voltage to a target voltage value.
Resistors are set in this circuit so that the output voltage may become 1.2V.
4.2.9.5.
48V(PoE)
→ 12V
IC402(PoE IC) starts the PoE classification when connected with the switching hub with PoE.
After the PoE classification ends, PWM conversion function of IC402 starts working.
IC402 controlls Q401 so that the voltage between pin6(SENP) of IC402 and pin4(SEN) becomes 1.5V,and adjust the output voltage
to a target value.
Resistors are set in this circuit so that the output voltage may become 12V.
After the PoE classification ends, PWM conversion function of IC402 starts working.
IC402 controlls Q401 so that the voltage between pin6(SENP) of IC402 and pin4(SEN) becomes 1.5V,and adjust the output voltage
to a target value.
Resistors are set in this circuit so that the output voltage may become 12V.
Note
As potential of PoE_VSS and DG in the schematic diagram is different,pay attension at measurement of volateg with PoE hub.
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