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DRV8718-Q1: Protection of SH inputs

Josef Warta
Expert 4300 points
Part Number: DRV8718-Q1

Hello Team, customer has following question:

I have question about protection of SH inputs of GDRV. In my design when resistive load (wire inductivity) was switched Off, the gatedriver was damaged thru SH input (pulse 25-30V). So, I want to add resistor (1-10K Ohm) in the series for limiting the current to coupling diode. After fault DRV8718 is getting hot and consuming permanently ~100mA

This sensing input is also used for diagnostic functionality (as low current source). Will this resistance interfere with diag. functionality?

Both use cases are only as High side switch (LSx is connected to GND thru 100k.)

 

Do you think that it will work?

Are 33R to Gate still required, or it’s safe to use direct connection to GDRV (GHx, GLx)?

Many Thanks

Josef

  • 0
    TI__Mastermind 19380 points

    Hi Josef,

    Josef Warta said:
    I have question about protection of SH inputs of GDRV. In my design when resistive load (wire inductivity) was switched Off, the gatedriver was damaged thru SH input (pulse 25-30V). So, I want to add resistor (1-10K Ohm) in the series for limiting the current to coupling diode. After fault DRV8718 is getting hot and consuming permanently ~100mA

    A pulse of 25 - 30 V should not "damage" the SH pins. 

    The absolute maximum SHx pin voltage is rated for 40 V. 

    Was the device damaged, or did a fault occur?

    Josef Warta said:
    Are 33R to Gate still required, or it’s safe to use direct connection to GDRV (GHx, GLx)?

    The 33R resistors are not required and could connect directly to the gate. 

    A 0 Ohm resistor is used on our EVM design for the DRV8718-Q1EVM.

    Best,

    David

  • 0 in reply to David Medis
    Prodigy 10 points

    Hello

    The GDRV was permanently damaged (hot, increased consumption) and after change it could be damaged same way. It's possible that for short time the voltage on SH was higher (>40V). What internal structure can cause this?

  • 0 in reply to Marek Stehlik
    TI__Mastermind 19380 points

    Hello Marek,

    Marek Stehlik said:
     It's possible that for short time the voltage on SH was higher (>40V).

    If the SHx pin experienced a voltage higher than 40V over a greater transient period than recommended the device could be damaged. The voltage on the SHx pin with respect to the DVDD or DRAIN should not exceed 40V. It is recommended to limit the negative voltages on the SHx pin to ensure any rise or spikes in voltage do not exceed the recommended ratings. 

    Marek Stehlik said:
    What internal structure can cause this?

    If a voltage spike occurs over the recommended operating conditions the following functions would be affected and lead to damage of the device. 

    IDRIVE ,overcurrent and threshold detectors could be affected. 

    An increase in thermal conditions would also have an affect leading to inconsistency and ultimately damaging the device. 

    Best,

    David