• LT3999 switch node voltage

    Hi All,

    I am using LT3999MP part in my design. As per datasheet, SW node voltages (at SWA and SWB) should be between -0.3V and 80V (screenshot below).

    The transformer that I am using has leakage inductance of 0.45uH. Based on simulations with LT3999…

  • LT3999 transformer

    Dear Sir/Madam,

    I am looking for some available transformer options.

    For nominal 12V input and 12V output the data sheet recommends Coilcraft PA6384.
    This part does not seem to exist. 
    The EVM uses Wurth 750314781. I cannot find stock.

    Are there any other…

  • LT3999, negative transient on UVLO input

    I'm using the LT3999 Push-Pull DC/DC Driver.  I'm utilizing a FET to hold UVLO signal to GND during system power up, then when the system is stable, the FET is disabled allowing the UVLO to monitor a voltage divided level of Vin.

    When the FET is…

  • Problem with LT3999


    Iam using the LT3999 in series with a push Pull Trafo from würth (750315371) to generate 12VDC isolated.

    After a powerup, the first few seconds all works fine but then the output voltage begins to oscillate and as a result, the LT3999 is getting…

  • RE: LT3999 programmed duty cycle

    Problem resolved...

    After simulated in LTSpice I find out that magnetizing inductance is not enough for my design requirements. But I use planar PCB transformer (four 4-turn winding, ~30uH calculated inductance).

    As you can guess I can not change transformer…

  • With regards to input capacitor for LT3999

    Hi , 

    I would like to know if i change the input capacitor to less than 4.7uF if the push pull load current is low .

    Please let me know if there some details on how to decide on the capacitor value for this device .

    We have customer who would like to…

  • LT3999 adjacent Tranformer


    i want to use LT3999 to build 12V and 0.8A power supply. according to datasheet i have to use a  COOPER BUSSMANN CTX02-19062  to adjust LT3999. but there isnt any transformer in this name around the internet. does anyone has information?

  • LT3999 Synchronous Rectifier and higher output current

    Hi there

    I'm in the process of designing a power supply using the LT3999 and have a few questions:

    1.) Can you recommend a synchronous rectifier  that could be used with the LT3999

    2.) Is it possible to enhance the output current capability? (I need…

  • RE: sync andinternal osc in lt3999

    Thank you again for your response. I connected a 4W push pull converter with Lt3999, and I see that the signal transitions at the switch nodes are very fast, is there any way to control slew rate?

  • Simulation of LT3999


    I am simulating the LT3999 with : Vin = 13V, Rt = 35k, Rdc = open, Txfr=200uH n=1:1.  The problem is that the output voltage won't ramp to its final value unless I add an output inductor after the output diodes.  Why is it required?