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SM72295: MOSFET Not Driven

Ammar shamsi
Prodigy 110 points
Part Number: SM72295
Other Parts Discussed in Thread: TIDA-00120

Hi,

  I am using SM72295 for a solar MPPT Charger. Our is referenced from TI reference design TIDA-00120.

 The problem is No MOSFET is getting driving pulse. LOA & LOB are at 0V, HOA & HOB are at around 12V i.e  at HSA & HSB potential.

 Please help me to find the points of mistakes I may be making.

 

  • 0
    TI__Intellectual 1880 points

    Hi Ammar,

    Thanks for choosing TI. I am a systems engineer and I will try to help you to resolve this issue.

    May I get the your schematic?

    I am sure you must have checked it but please make sure that none of protections are kicking-in and all the threshold requirements are met. All the amplifier inputs are outputs need to be terminated properly.

    If you are not using the TIDA design as it is, would you please share the differences?

    Let us start with this and work toward the solution.

    Regards,

    Ritesh

  • 0 in reply to Ritesh Oza
    Prodigy 110 points
    Dear Ritesh,
    Thank you for your quick response.
    I have noticed the I.C we are using has marking S72295 not SM72295 and to TI trademark on it. We ordered SM72295 samples from Mouser. I doubt we may have received wrong part.
    Could you help me know that whether the original SM72295 has TI marking?
    I am attaching the I.C picture.
  • 0 in reply to Ammar shamsi
    TI__Intellectual 2910 points
    Ammar,

    I am a colleague of Ritesh's. The marking of "S72295" is correct for the SM72295. Sometime we need to remove some characters from the marking in order to fit it in the package. Seems like you have the correct device.

    Have you had a chance to put together the info that Ritesh requested above?

    Regards,

    - Daniel
  • 0 in reply to Daniel Ruiz
    Prodigy 110 points
    Thankyou Deniel
  • 0 in reply to Ammar shamsi
    Prodigy 110 points
    Dear Ritesh,
    Please have a cross check on it. Please let me know if any modification required.
  • 0 in reply to Ammar shamsi
    TI__Intellectual 1880 points
    Hi Aamar,

    Thanks for the patience. I noticed that the pin 5, which is AGND pin, is left open. It must be tied to analog ground.
    Also generally unused input pins should be grounded.
    Did you check all bias supplies are above their respective thresholds.
    Also did you check all inputs are above their respective thresholds.
    As there is a bootstrap supply involved, low side output has to come first to charge the bootstrap capacitor so that high side bias is available to turn the high side output ON.
    Also did you check pin 15 to see if it is in OVP mode?
    Check voltage on pin 16 to make sure that the voltage is below shutdown voltage.
    Rest of the schematic looks normal.
    Let us try these and then we will move on. Most probably grounding pin 5 should solve the issue.

    Regards,
    Ritesh
  • 0 in reply to Ritesh Oza
    Prodigy 110 points
    Hi Ritesh,
    We had corrected PIN5 connections to Ground before testing. We have disconnected R43 to avoid OVP shutdown, But still it is not working.
    What can be the other causes?
    Thanks & Regards
    Ammar Shamsi
  • 0 in reply to Ammar shamsi
    TI__Intellectual 1880 points
    Hi Ammar,
    If that is the case, I suspect one or more thresholds are not being met.
    Did you look at voltage at all the pins?
    Meanwhile, let me check with our design team and see if they know any special for driver not to function normally.
    Regards,
    Ritesh
  • 0 in reply to Ritesh Oza
    Prodigy 110 points

    Hi Ritesh,

      The I.C started working, We tested it with 20KHz PWM with 80% duty cycle It worked o.k after sometime when we increase PWM frequency to 50KHz the S72995 becomes hot and stops working within 5 minutes of working. We replaced the I.C then the same happened to the second I.C.

    Please make me aware of the some suspicious points for the mistake,I may be making.

     

  • 0 in reply to Ammar shamsi
    TI__Intellectual 1880 points
    Hi Ammar,

    That is good. May I know what was preventing it from generating output?
    Regarding IC getting hot, may I know the schematic and power MOFETs you are using, as this post do not have that information.
    You mentioned that after 5 minutes IC stops working. Does it start working again if you were to recycle the power or let it cool down?
    If not, did you find which pins get damaged?
    At ambient temperature of 25C, the IC should handle about 1.6W without any issues based on thermal impedance mentioned in the datasheet.
    Are you supply VDD and VCC from the same source?
    Did you try to change VCC?
    Let us take a loot at these details and then we can proceed further.

    Regards,
    Ritesh
  • 0 in reply to Ritesh Oza
    Prodigy 110 points
    Dear Ritesh,
    Now the I.C is working there was some in the PCB.
    Now the problem is the SM72295 I.C is being damaged after some time. We have damaged 5-6 I.Cs some times it is damaged after 1-2 days operation, sometimes with in 5 minute. We are using TI Solar MPPT Reference Design
    TIDA-00120 for the hardware reference. Please help us to resolve the issue. It will be great help if any TI/ TI supplier support us in Delhi.
    Thanks