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DRV8313 Isolation Question

Gail Dagan1
Prodigy 115 points
Other Parts Discussed in Thread: TMS320F28069, DRV8313

I am using a TI DRV8313 to drive a 3-phase BLDC motor; our controller is a TI TMS320F28069.   Our VM is 24V and most of the rest of the system is running at 3.3V.   We are experiencing VERY occasional catastrophic electrical events in which it seems like the high voltage energy is getting into the 3.3V system and blowing up the processor.  After ruling out design, layout or mechanical (interference/shorting) issues we are starting to suspect the 3.3V digital signals that interface from the processor to the DRV8313, or the motor current sense signals that interface to the analog inputs of the processor.  

Do you know if there is any isolation in the DRV8313 control logic or pre-driver blocks?

Is there a recommended way to isolate an analog current sense signal?

  • 0
    TI__Mastermind 21305 points

    Hi Gail,

    Can you post your schematic? We can arrange to message it privately over E2E messaging if needed. The DRV8313 should protect the IO lines from any high voltage signals.

    Are they any specific pins on the processor being damaged?

     

  • 0 in reply to Nicholas Oborny
    Prodigy 115 points

    I can e-mail you my schematics, but can't post them to the web.  The two areas on the chip that look damaged are around pins 35-40 and 90-95.  Please let me know how to confidentially send you a PDF of my schematics.

  • 0 in reply to Gail Dagan1
    Prodigy 115 points
    Also, when we do have a problem, it is right at power-up, not when things are actually moving.
  • 0 in reply to Gail Dagan1
    TI__Mastermind 21305 points

    Hi Gail,

    Some followup questions. The C2000 damage appears to be quite severe so I am not sure if the pin locations tells us much.

    1) What type of power supply are you using? What is the ramp rate of the power supply when it is enabled?

    2) Is there any damage to the DRV8313? If you replace the C2000 does everything function correctly or are there other components with damage?

    3) I see there are several voltage monitors (12V and 24V). Is there any chance these exceeded the abs max rating for the C2000? We generally recommend some kind of diode clamp to the MCU supply for any ADC line into the C2000 that might see high voltage.

    4) Is there a specific purpose for taking a high side current shunt measurement and converting to a ground referenced measurement for the DRV8313?

  • 0 in reply to Nicholas Oborny
    Prodigy 115 points
    1. 24V to system is supplied by wall wart to a different PCB which has a LTC4359 reverse and over-voltage protection circuit. The 24V from there goes through a connector to get to this board. 12V is also created on that board with a DC-DC regulator and goes through a connector to get to this board. 24V ramps 0-24V in 50usec.
    2. Can't tell if DRV8313 is damagaed. Haven't sent in board for a new processor.
    3. Checked voltage spike on 24V rail at power up. With the divider network I have it's sometimes close to absolute maximum rating. I found the TI DOC SPRAAP6A Analog IFC to TMS320F*. I'll look into implementing diode clamp on the next spin of the board.
    4. Software algorithm guy has reason for wanting to read the currents there. I can put you in touch if you want to message with him.