LTC4266 IC is damaging repeatedly in our product

We have designed a PoE module using LTC4266 IC and recently we have been observing that LTC4266 IC is burning after running for some time.

Suggestions and comments are highly appriciated

Attached schematics for reference

PDF

  • Hello,

    There does not seem to be an LTC4266 in the attached schematic. There is an LTC4259A-1, one of our first PSE controllers. LTC4266 is pin compatible with the LTC4295A-1, but it has more features and can support higher power levels. Are you in the process of changing the design?

    Best Regards,

    Eric

  • Hi,

    Thanks for the response.. Yes, in attached schematic LTC4259A-1 is there but as these two LTC4266I and LTC4259A ICs are pin compatible, we have designed schematic to be compatible for both. currently we have assembled LTC4266I in the board and in one of our customer place this PoE controller is burnt in few boards.

    we suspected surge/ transient voltages for the failure and conducted surge test on Ethernet lines up to 2KV(1.2/50us and 10/700us) and and no failure observed.

    If there are any cares to be taken or missing in the schematic please suggest.

  • The LTC4266CGW shares the same footprint and has similar pinout as the LTC4259ACGW-1.  The LTC4266CGW can be swapped on to an existing LTC4259ACGW-1 board with the following changes.

    • Change IC to LTC4266CGW
    • MID (pin 2) shunt to ground
    • DETECT1-4 (pins 11-14) left floating
    • Change port sense resistance to 0.25Ohms
    • Shunt 10k at each OUTn (pins 34, 31, 27, 24) to connect directly to port output
    • Shunt AC blocking diode in power path of each port
    • MSD (pin 36) left floating

    Refer to the Surge Protection section in the LTC4266 datasheet for recommended surge protection components.

    The LTC4266 has a long history of robustness and reliability.  Please submit the part in for a Failure Analysis for a full report to better understand the failure.

  • Sure, we will re-check the changes to be made for replacing IC LTC4259 to IC LTC4266.

    Can you please confirm where do we need to submit this part for failure analysis? or are you suggesting us to do the failure analysis.

    Thanks,

    Ananda