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SM72295EVM: High side (HOA, HOB) gate drivers not working

Marco Lutteri
Prodigy 10 points
Part Number: SM72295EVM

Hello

I cannot drive the high side MOSFETs (DC or with a 16kHz PWM) because the HOA/HOB lines are always at VCC and don't respond even to the OVS signal, which correctly turns LOA and LOB lines off.
I tried grounding HIA and HIB but HOA and HOB are always high. Also disconnecting the MOSFET gates from the driver doesn't make any difference.
Changing the IC didn't solve the problem either.

Please help!

Thanks, Marco

  • 0
    TI__Genius 9451 points

    Hi Marco, 

    Thank you for your question. A couple of things to check:

    • Please check the VCC and VDD voltage levels (should be 10V and 3.3V respectively). What DC Vin voltage are you using? The EVM user's guide, section 2.3 "Setup" mentions that Vin should be within the 12V to 48V range.
    • Do you have the MOSFETs connected in half bridge configuration? The FETs need to be connected in this configuration as the bootstrap capacitor connected between HBx and HSx pins relies on the switching of the low side FET to charge and power the high side driver. You can see more details about bootstrap circuit functionality in this apps note: https://www.ti.com/lit/an/slua887/slua887.pdf

    Best regards,

    Leslie