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LM5116 standby to on temperature stability

Brett Breitinger
Prodigy 20 points
Other Parts Discussed in Thread: LM5116

Hi, I am doing design verification on some prototype circuit boards that use the LM5116 to supply 28V at 1A max with an input voltage of 42V nominal.

The circuit needs to go from standby to on, covering the temperature range from -40C to +85C.  With a sample size of two circuit boards one of them is stable from 

-40C to just above room temperature, and the other one works from  -30C to +85C.  I find it improbable to have both parts failed due to temp testing.  Suspect that 

the board with the regulator unstable just above ambient to be a failed part.  

My thought on the second board is that possibly the values and /or the  type (dielectric material) of some of the external components needs to be changed for

temperature stability.  How do I identify and calculate the values for these parts, or are there other things that I should be checking first?  I noticed on the LM5116

datasheet that the EN threshold and other parameters change over temperature.

  • 0
    TI__Guru 58971 points
    Hi

    Would you describe in detail about the unstable operation you are talking about? or if any waveform captures, would you please share?

    Regards,
  • 0 in reply to EricLee
    Prodigy 20 points
    Hi, thanks for your reply. After reviewing a number of waveform captures of the interface circuity, and the enable and output pins of the LM5116 we have found the answer to the temperature standby to on issues. For the -40C failure we determined that our interface micro-controller was disabling the enable pin of the LM5116 due to a suspected firmware error; it works when placed in a different test mode. For the +85C failure, our over-current protection circuit was activating on a false over-current condition; works after correcting the problem with the circuit.