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LTC4291-1 & LTC4292 Issue


We are using LTC4291-1 and LTC4292 in our PSE application. While connecting the the PD through LAN I don't get output. Gate pin stays low always. Below waveform (10x) is the one I'm getting on OUT1A when connecting PD. When PD is not connected  a sawtooth waveform is observed at this pin. In the LTC Qev GUI , it shows "Rsig low"  in the respective port. I have verified the schematic it seems ok. Can you guys help this out? . If you need schematic to look over this I will send it to email if you share one. 


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  • Maybe i didn'g explain my probelm clearly;   when i use LTC4292 supply LTC4321 (the demo is DC2685), the connecting is ok ,and the led of OUTnm is ok; But i use the Gerber document for produce a ciruitboards and buy components ,finding " In the LTC Qev GUI , it shows "Rsig low"  in the respective port."  ;

    the problem is stange; the datasheet shows " Port Detection Status  :Rpd<17K",what's the probelm?

    the datasheet shows as following:

    The LTC4291-1/LTC4292 is designed for a low 0.15Ω current
    sense resistance per channel. Two parallel 0.3Ω resistors
    must be laid out as shown in the Layout Requirements
    section. In order to meet the IHOLD-2P, ICUT-2P, and ILIM-2P
    accuracy required by the IEEE specification, the sense
    resistors should have ±1% tolerance or better, and no
    more than ±200ppm/°C temperature coefficient.

    Is the resistance problem?