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Original question:

DRV8353: Gate drivers dying

DRV8353: Middle point voltage

user4976416
Prodigy 60 points
Part Number: DRV8353

Hi,

We are using the driver to control 2 mosfet half bridges. When the system is energized (not switching) the voltage in the middle point of the half bridge becomes 6.9V (SHA and SHB). We guess that voltage is coming from the driver, is that nominal beaviour? If that is a constant voltage provided by the driver, a large current will be drawn when a load is connected.

  • 0
    TI__Guru 61260 points

    Hello!

    There is naturally a small leakage from the VCP node internally through the high side FET pull-up and out to SH when the Low side FET has not been switched. This current is 200-300uA maximum and will dissipate once the LS FET is turned on.

    I also see above that you have IDRIVE configured as the MAX, Can you show us your FET bridge connections and the model number of your FETs? What is your expected VDS rise and fall time? The reason I ask is because this IDRIVE is too high for most applications and it can cause issues if not setup correctly.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 60 points

    Hi Adam,

    As the transistors and the driver are on different PCBs the signals' name does not match but hopefully it will be understandable. As you see, we have 3 MOSFETs on top and 2 MOSFETs in the bottom. The model is IPB044N15N5. We have a gate resistor which we plan to optimize, with a 22Ohm resistance the turn on time was around 130ns. We will reduce the resistance as much as possible to reduce switching losses as far as the ringing is acceptable. We understand that in case that the resistor is removed, then the driver should limit the current, is that right?

    Could you describe the issues of not setting up the limit properly?

    Also, the pin GLB became shorted with SPB, effectively leaving the driver useless, after some time of testing. The diver was working as expected before this happened. Voltage Vgls is low and has spikes to even lower voltage. We removed the traces in the PCB so the issue is probably inside the driver. Could you provide hypotesis of what might have caused this issue?

    Best regards.

  • 0 in reply to user4976416
    TI__Guru 61260 points

    Hello,

    When using multiple FETs per gate output it is essential to use gate resistors in order to limit the gates fighting for charge from one source.

    If IDRIVE is too high, the gate and source nodes can ring/overshoot/undershoot and cause damage to the DRV, more info here: https://e2e.ti.com/support/motor-drivers/f/38/t/796378

    The device damage you are seeing hints that the IDRIVE is too high or there is excessive overshoot/undershoot/ringing on the gates and sources that are damaging the driver.

    Regards,

    -Adam