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DRV8301 and Gate resistors

Daniel Munoz
Prodigy 110 points
Other Parts Discussed in Thread: DRV8301

Hi everyone,

Could the gate driver of the DRV8301 get broken because of not having a resistor in series with the MOSFET gates? It seems to be the origin of my problems. My PCB has worked before with smaller MOSFETS without a gate resistor, but now with bigger ones has only worked once, and then dead. I am getting FAULT and GVDD_UV. GVDD remains at 2V.

Regards.

Daniel

  • 0
    TI__Guru** 114905 points

    Hi Daniel,

    Can you provide more information?

    Were the FETs damaged on the board also?

    Can you provide a schematic and layout?

    What is the PVDD voltage? Is it possible that PVDD saw a spike above the absolute maximum?

    Also please take a look at the post ( LINK ),  where another user described a similar problem. In this case, inductive spikes were created damaging the DRV8301. The method used to correct the problem was also stated.

  • 0 in reply to Rick Duncan
    Prodigy 110 points

    Hi Rick, thanks for the quick response. The FETs have been replaced and nothing has changed. They are rated at 160A. They input voltage comes from a regulated power supply at 15V (quite below the maximum) and a current limit of 5A. Tha capacitor on GVDD is not the one in the schematic, but a 4.7 uF 100V ceramic one.

    The schematic is here. I am not allowed to post the layout as is.

    INV_V2.0.pdf

    Very interesting post the one you linked before. However, I still have 2V on GVDD when powered on, and the SPI is throwing coherent values for Control and Status registers. So I dont think there is a PVDD issue.

  • 0 in reply to Daniel Munoz
    TI__Mastermind 21305 points

    Hi Daniel,

    GVDD should be ~11V typical. If GVDD is reading 2V then something has gone wrong.

    Can you post the PN of the MOSFET that gave no issues and the MOSFET that had issues. It would be good to examine the differences.

    I would recommend changing the GVDD capacitor to the recommended 2.2uF just to rule that out.

    I would also take an o-scope and examine the gate drive slew rates (GH, GL, SH). Most issues with the DRV8301 results from switching the external MOSFET to fast. You can slow down the slew rates by lowering the gate drive strength setting and adding series resistance.

    At fast slew rates, parasistic inductance in the half-bridge will cause voltage spikes (both positive and negative). These can be quite extreme. This is improved with reduced slew rates and improving the layout around the half-bridges.

  • 0 in reply to Nicholas Oborny
    Prodigy 110 points
    Hi Nick, thanks also for your response.

    The "smaller" MOSFETs are IRFR1205. The "bigger" ones are IPB036N12N3 G. The gate drive current was set to 0.7A. At this point, I would also like to ask what does "for slew rate control" mean on the control register description? ("Gate driver peak current 1.7A (for slew rate control)") Does it mean that care must be taken? Or does it mean that the DRV makes some slew rate control? In this last case, why does it fail to protect itself from a high slew rate with other configurations?

    I will try replacing the DRV and installing a series resistance. Do you think 100 ohm would be sufficient? I know it influences the dead time requirements, but lets start with say the maximum of 500 ns dead time (3-input mode).

    Daniel
  • 0 in reply to Daniel Munoz
    TI__Mastermind 21305 points

    Daniel,

    The slew rate current strength affects how fast the gate of the external MOSFET turns on. An extremely fast slew rate can cause voltage ringing on the external half-bridge due to parasitics in your layout and the MOSFETs themselves. This ringing can potentially damage the DRV8301 if it is severe enough (it cannot protect against this, it must be managed in system design).

    The gate charge (Qg) of the "larger" MOSFET is actually 3x the smaller MOSFET, so you may actually be under driving the MOSFET. The best way to check this is to examine the gate drive voltages and see what is actually happening. I would do this first before making a change. We need to understand what is actually happening between the two MOSFETs

    I would not install more than 1-30 ohms of resistance.

  • 0 in reply to Nicholas Oborny
    Prodigy 110 points
    Hi Nick,

    New DRV8301, and 15 Ohm series resistance on the gates and the problem was solved. The ringing seemed to be strong enough to damage the DRV.

    With the o-scope a big ringing could be seen with the bigger MOSFETs. The layout is not specially optimized to reduce the parasitic inductances, however the distance between the DRV and the gates is small (less than 2-3 cm - 1 inch - to the furthest MOSFET). So I guess this is a relative common problem.

    Now it makes a nice switching curve, almost without damping, and works flawless.

    Thanks for the help. Your experience is appreciated