• Does LTC4269-1 support power demotion?

    Does LTC4269-1 support power demotion? Power demotion was introduced in IEEE 802.3at. LTC4269-1 is a IEEE 802.3at compliant PD. Suppose I have defined LTC4269-1 in my circuit as a type 2 class 4 PD (Rclass = 30.9 Ω). If I connect the LTC4269-1 to a…

  • LTC4269-1 current spikes

    I'd like to use the LTC4269-1 (LTC4269IDKD-1#TRPBF) in a design, but I'm seeing current spikes that are too high on the eval board (DC1335B-C). How can you explain this and what can I do to reduce them below the peak current threshold (684 mA)?…

  • RE: LTC4269-1 with cisco switch Catalyst 2960 series

    What is the RCLASS resistor set for at the LTC4269-1?

  • LTC4269-1 start-up problem

    Why do I have an unstable output using the LTC4269-1?  What you see in the scope is measured between +12VE and DGND. Refer to my schematic. Other than equivalent component replacements, it matches the DC1335B-C evaluation board. I've also attached my bill…

  • LTC4269-1 output current issue

    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.

  • What is the most elegant way to use the LTC4269-1 with an 30 V auxiliary supply?

    What is the most elegant way to use the LTC4269-1 with an 30 V auxiliary supply? Take the Demonstration circuit 1335B-C, (DC1335B-C) as your starting point This is a high-power supply featuring the LTC4269IDKD-1, LTC4269-1. I need to plan for the scenario…

  • RE: LTC4269-2 vs. rapid discharge of input capacitor

    LTC4269-2 would shut off the internal MOSFET, due to undervotlage lockout once VPORTP to VPORTN drops below 30V.

    Best Regards,


  • RE: When should I use soft-start on the LTC4269-1?

    Using Soft-start is optional but recommended when there is a large output capacitance. Soft-start will not allow you to reduce your VCC capacitor and avoid VCC from drooping during startup. Soft-start limits the current in the primary switch but it does…

  • LTC4269 output cycles, why?

    I'm trying to debug a PoE circuit which is pretty much a clone of the application example on page 31 of the datasheet. The main difference is that the output voltage needs to be 12V so the transformer is a PA2694 and the resistors around the TLV431 that…

  • generating VIN for LTC4269-2


    In the schematics of the "typical application" of LTC4269-2 the chip's supply voltage VIN rail is charged through a 33k resistor (the only source when not switching). Is that done just because that's the simplest and lowest cost solution, or are…