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LTC4269-1 output current issue

Question asked by anqiang on Apr 28, 2018
Latest reply on May 2, 2018 by anqiang

Hi all,

 

I am debugging my LTC4269-1 POE power board, and encounter some problem, is there any one can help us that would be appreciate. 

 

Problem as below,

 

If i disconnect the load, the POE power(LTC4269-1) output 11.9v,  seems every thing is right.

but if i connect the POE output to my digital chips,  in the begin the POE power also output about 11.9v, but after about ten minutes,some times the output drop to 10v , some times almost drop to 0 make the LTC4269 restart. 

 

My design is 48V input and 12v/2A output, schematics and device selection are same with the reference design. it should be have 24w output capability. but I use 7ohm power resistor replace the digital chips, the POE output also almost drop to 0 make the LTC4269 into start -restart cycle. i think It must can't drive 12W load and my board is about 2W, so some times the POE output drop to 10v. 

 

Why my design just have about 2W output capability?  what's the critical point might cause the problem that i can check?   

 

attached is the schematics,  thanks.

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