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Original question:

SM72295: MOSFET Not Driven

SM72295: Bootstrap Is getting damaged

Mitesh
Prodigy 190 points
Part Number: SM72295

Hello,

I am getting an issue in some cases, The output of HOA is getting distorted same as HBA and HSA , not getting proper ground . and after replace of SM72295 HOA output is getting proper ground.

  • 0
    TI__Guru**** 189401 points
    Hi Sanjay,

    Sorry to hear you are having difficulty with our device. What values do you have for C5 and C6 on the first page of the data sheet?
  • 0 in reply to Don Dapkus
    Prodigy 190 points

    Value of C5 and C6 is 4.7uF/50V

  • 0 in reply to Mitesh
    TI__Genius 12990 points

    Hi Sanjay,

    thanks for reaching out on e2e, sorry to hear about your issues SM72995.

    I understand that these are waveform's of HOA output when SM72295 is damaged and when replaced. The damaged HOA waveform has a slow rise/fall time and only has the ability to drive about 1us. After 1us the HOA output oscillates possibly from the high-side driver supply not driving it correctly. We need to make sure the driver supply has the right capacitor values on HBA-HSA and VSSA-PGND. What is the bootstrap and VCC capacitor values of side A?  is side B of SM72295 also have the same issue? is this a solar charging application? what is the load current?

    thanks,

  • 0 in reply to Jeffrey Mueller
    TI__Genius 12990 points
    Hi Sanjay,

    Just checking to see if your still experiencing this issue on SM72295?
    If not, how did you fix the issue?
    I can mark this thread 'TI Thinks Resolved' however you can reopen this thread by replying to this post.
    let me know if you have any more questions on SM72295.

    thanks,
  • 0 in reply to Jeffrey Mueller
    Prodigy 190 points
    Hello sir
    Yes i am using for solar charging application , bootstrap cap value is 1nf and the load current is only 5A . I am not using Side B , i am using only side A and side B is Normally open.
  • 0 in reply to Mitesh
    TI__Genius 12990 points
    Hi Mitesh,

    thanks for your update,
    Please check out the first page of the datasheet (www.ti.com/.../sm72295.pdf) which has a typical application circuit with typical values for the bootstrap and VCC capacitors. Typically, the bootstrap cap should be 470nF and the VCC cap should be 1uF. This should help with the ringing your seeing, which could be an LC ring from the 1nF bootstrap cap and a similar 1nH parasitic inductance in the bootstrap turn on path. Please let me know if changing these capacitor values helps your issue or you have any more SM72295 related questions.

    thanks,