I am reading the datasheet of MP8007. I found ambiguity in section
Wall Power Adaptor Detection and Operation on Page 16. After reading the section, i am not able to understand how IC will differentiate between voltage from Adapter and
PSE. Consider the equation given below:
Where, Vadp is adaptor voltage, Vdadp3 is the zener voltage, Radpup and Radpdown are the AUX divider resistors from adaptor power.
Considering the example given in Page 20 under section
Wall Power Adaptor Detection Circuit (Radpup = 3K, Radpdown = 8.06K and Vdadp3 = 30V), the IC can safely accept voltages from 38.48 to 53.98 V (even more than that).
Now, I am confused how will the IC gets to know that voltage is from Wall adapter or from PSE? Because PoE voltage range is from 44 - 57V and since, there is common voltages between adapter supply and PSE power supply and the wall adapter power is also applied at Vdd pin of IC (as with PoE).
The detection circuit is given below: