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Original question:

LM34910: Power supply fails if we use alternate components

LM34910C: 48V input,12V output 800mA problem

m.yuksel
Prodigy 20 points
Part Number: LM34910C

I maked design as shown datasheet and app note prefered. So SW pin signals is ok. FB has a problem. IC going to safe mode or OVP mode i think.

I searched, 2 people has same problem. Maybe this is design problem. I tried many recovery diodes, same problem.Diodes Vf 500mV to 900mV

first way to work, lower inductance, my design has 100uH, when i used 47uH it works but coil going to heating.
second way to work, adding 2" cable to recovery diode and place near the coil. that will work. I checked signals, fb pin has a distortion when sw fet working.

I used many type of diodes, Vf about 500mV to 900mV, series. Also i tried current sense resistor, 680mR and 330mR, and shunt the current sense. this is FB pin problem.

Any one try to help?

  • 0
    TI__Mastermind 25590 points

    M.Yuksel,

    Do you have a voltage on the output when you start up the LM34910C? If so, this thread details what is happening. In short, the part may not start in a pre-bias condition.

    If not, please give me a detailed list of your test setup. What are the voltages on the pins for your sequence before, at, and after the issue you observe.

    -Sam