• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 335 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM2576HV: faliure after running for long durations

ravi babu50
Prodigy 70 points
Part Number: LM2576HV

Hi,

we are using LM2576HVT-ADJ in one of our boards, after running for several months at the customor site 10 boards out of 1000 were reported regulator failure.

 input:- 40 to 50V

output:- 27.3V

current:- 2.5A

 from our analysis we found that when there is a AC loss, we are shutting down the  LM2576HVT by pulling the Pin-5(ON/OFF) high and the board works with Battery power(24V).

The Battery_voltage(24V) is feedback to the outpin/input of LM2576HVT as there is no isolation. will it cause any issue with the reguator working.

U23_regulator.pdfAttaching the schematic please review and let me know if its ok.

Thanks in advance.

  • 0
    TI__Mastermind 35210 points

    Hello Ravi,

    With power cycle, does the regulator work after or is the failure destructive?

    If the IC is replaced, does the device function?

    Does design verification ensure that device ABSMAX is not exceeded on the input?

    What is part number of output filter inductor?

  • 0 in reply to Marshall_Beck
    TI__Mastermind 35210 points

    Additionally, a schottky diode is recommended  for D19, to allow for minimal power power consumption in device if device HS body diode (from VIN to SW) becomes forward biased due to VIN being a diode drop below VOUT.

    Schottky low forward voltage enables the majority of current to go through it, rather than the body diode.

  • 0 in reply to Marshall_Beck
    Prodigy 70 points

    hi marshall,

    Thanks for the reply, here are the details you asked.

    With power cycle, does the regulator work after or is the failure destructive?

    • No the IC does not work after power cycle.

    If the IC is replaced, does the device function?

    • Yes, it works after replacing with new IC

    Does design verification ensure that device ABSMAX is not exceeded on the input?

    • Our max input voltage level is 50V

    What is part number of output filter inductor

    • P/No:- IIHB3EB331K(INDUCTOR,POWER,330UH,10%,4.5A,DRUM,RAD)

    Thanks in advacne

  • 0 in reply to ravi babu50
    TI__Mastermind 35210 points

    Hello Ravi,

    Answers to the questions were helpful.

    Common causes for device failure are due to overstress on device, overstress meaning, power applied through device exceeds silicon characterized absolute maximum and recommended conditions.

    It is up to the system design, but often is recommended that some form of input voltage protection is placed on the input, ie: TVS diode

    In addition, I saw your diode part number IHB3EB331K, looking at datasheet specification, appears it is rated for max DC current of 3.2A. I speculate that it is ferrite core inductor, whose saturation curve rolls of very hard above the saturation point. I believe that saturation point to maybe be 4.5A? (Not able to locate in datasheet).

    With that said, if inductor is heavily saturated, which could occur during current limit, where peak inductor current can be up to 7.5A per the datasheet, electrical stress can be put on the inductor, in addition, as inductor will have very low effective inductance, the upwards slope on the inductor ramp current may become very large, causing the device to have difficulties in controlling the current, possibily destructing either the inductor and device, or both.

    I would see if you could simulate a failure perhaps. Can you apply several short circuit condition, at highest ambient temperature your design is confined to?