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DRV8305-Q1: Problem With Driver Output

Prodigy 140 points

Replies: 27

Views: 605

Part Number: DRV8305-Q1

Hello, to whom this may concern,
I am trying to develop a custom board using the DRV8305N and I'm facing some problems. Although nFault pin is high, I get no response on the output, except for a dc of 5.6v on every output pin.
Some infos about my hardware:

PVDD = 10v

INHA = PWM around 20kHz, 50% duty-cycle

INLA = INHB = INLB = INHC = INLC = 0 vols.

This setup consumes around 23 mA.

There's no Mosfet soldered yet, only the minimum hardware to get the driver working.

Please, I would like to understand what that means, I've tryed to apply 8v and 6v and all the outputs keep as 5.6v fixed. The driver emits a noise that resambles commutation, but there's no mosfet soldered, as I've said before.  

  • Emanuel,

    I would suggest using the device EVM. FETs are needed because the protection features will be checking for Vds and Vgs when attempting to switch. 

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Can  I add 2 mosfets only while I test the driver features? Or do I need to add all 6?

  • In reply to Emanuel Soares:

    Emanuel,

    All of them are needed as the protection features will check all 6 outputs and all 3 phases.

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Adam,

    Other question: I am using 22 ohm resistors between the gate and the GHx and GLx ports (in all of the mosfets), is that a big issue?

    Sincerely,

    Emanuel

  • In reply to Emanuel Soares:

    Adam,

    The chip seems work fine.The interesting thing is that with only 1 half bridge welded it worked fine. The only problem now is the temperature, the chip gets stable, but quite hot, is that normal?


    Sincerely,
    Emanuel  

  • In reply to Emanuel Soares:

    Hi Emanuel, thanks for the feedback.

    The chip should not be running hot. Is the temperature comment based on the EVM or on your custom board ?

    If this your custom board, then we would recommend checking the thermal pad soldering since the IC relies on this for heat dissipation. If this is the case, we have several PowerPad design recommendations. As goo starting point is the application note below

    . PowerPad Made Easy

    Regards

    Anuj Narain

  • In reply to Anuj Narain:

    Anuj Narain,

    That was about my custom board. I did not design the thermal pad it was supposed to have, cause my board do not have much space. 
    Although it is still running well, with stable current consume. 

    Regards,
    Emanuel

  • In reply to Emanuel Soares:

    Hi Emanuel, 

    Great. That sounds like it is the problem. As you start to design your board we have a PCB layout guide that other customers have found useful. You know where to find us if you need help. 

    [FAQ] Best Practices for PCB layout of Motor Drives

    Also, 

    If your issue has been resolved, please help the E2E community by clicking the green “This Resolved My Issue” button.

    If you have a related question, please use the orange "Ask a related question" in the top right corner of the page.

     

  • In reply to Anuj Narain:

    I have a feedback about the driver: The chip (DRV8305N) seems work fine, it finally responds to the SPI communication, tested with no motor terminal plugged in. 

    With no motor plugged in, although the outputs on the 3 terminals, each between 2 mosfets in the same half-bridge, have right behave according to the datasheet, when I plug the motor, it makes the driver burn. It stopped to respond to the SPI data, and stopped working. The only thing I did was to plug the motor. Before this, it was just working fine.

    Notice that the DC bus connected to the Drain of the High side of the 3 half-bridges is connected also to the PVDD.

    To someone that could help me.  

  • In reply to Emanuel Soares:

    Emmanuel, 

    Do you know what was damaged? Have you taken any measurements of the damaged IC?

    Did you improve your power pad?

    Regards,

    -Adam