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DRV8908-Q1EVM: POLD problems

Zoey Wu
Expert 5835 points
Part Number: DRV8908-Q1EVM

Tool/software:

hi team,

my customer is using DRV8908-Q1EVM, and the problem is as below. Could u kindly help to give some advise? thanks!

firstly they have already configured the demo with GUI and connect the demo to 30V supply. The EXT_OVP turned to 1.

and then they configure the 6 individual bridge with open load.

following the step to configure POLD as the datasheet P53.1)configure the HBX_POLD_EN in OLD_CTRL_5 register and enable the passive OLD of 1-6 channels; 2) configure  HBX_HS_EN/HBX_LS_EN, enable the high side switch of 1-6 channels; 3) configure POLD_EN;

but no fault was report after also these configuration. the same problem occurs when they use their own board. Do u have any advise? thanks!

  • 0
    TI__Mastermind 19300 points

    Hi Zoey,

    Just to confirm, they want to enable Passive OLD and configure high side switch of 1-6 channels?

    Are they expecting to see a fault?

    Is there a load attached to the outputs?

    Best,

    David

  • 0 in reply to David Medis
    TI__Expert 5835 points

    Hi David,

    Yes, there are no loads attached to the outputs , and they expect to see a fault.

  • 0 in reply to Zoey Wu
    TI__Mastermind 19300 points

    Hi Zoey,

    Let me try this out in the lab and I'll get back to you tomorrow. 

    Best,

    David

  • 0 in reply to Zoey Wu
    TI__Mastermind 19300 points

    Hi Zoey, 

    Are they running the downloaded version of the GUI or the Web version?

    What is the version of the GUI?

    Best,

    David

  • 0 in reply to David Medis
    TI__Expert 5835 points

    Hi  David,

    pls see the version as attachment.thanks!

  • 0 in reply to Zoey Wu
    TI__Mastermind 19300 points

    Hi Zoey,

    Try checking the OLD button through the information button.

    The OLD Enable button should be enabled in order to detect open load conditions. See if toggling this button is responsive in the register settings.

    Best,

    David

  • 0 in reply to David Medis
    TI__Expert 5835 points

    Hi David,

    thanks for your reply!

    but it shows no influence to the result.

    is it possible that the POLD is deleted as the other parts such as DRV8912? Do u have any other advise? thanks！

  • 0 in reply to Zoey Wu
    TI__Mastermind 19300 points

    Hi Zoey,

    When configuring the POLD it is important to follow all the steps listed in the datasheet. I've listed the steps below and highlighted the steps that are often overlooked. 

    Has the customer followed these steps in sequence:

    Following are the steps to configure and detect the passive OLD in the DRV89XX-Q1 device.

    1. Enable the passive OLD mode for the individual half-bridges which is to be diagnosed using the Half-bridge passive OLD enable bits (HBX_POLD_EN) in OLD_CTRL_5 register.

    2. Configure the half-bridge operation control bits (HBX_HS_EN/HBX_LS_EN) in operation control register (OP_CTRL_X) to determine the high-side and low-side OLD check. Note that these bits are now used for the passive OLD configuration. If anytime, the HBX_POLD_EN is reset then the bridge starts operating.

    3. Enable the passive OLD using the Passive OLD Enable bit (POLD_EN) in CONFIG_CTRL register. Setting the POLD_EN bit enables the passive OLD detection circuit on all OUTx pin for which the corresponding HBX_HS_EN or HBX_LS_EN are set to 1.

    4. Wait for the passive OLD time as determined by the user.

    5. After the completion of passive OLD time, disable the passive OLD enable bit (POLD_EN).

    6. Monitor the nFAULT pin / OLD bit in Status register (IC_STAT) and the HBX_HS_OLD/HBX_LS_OLD bit in the OLD status registers (OLD_STAT_X) for any open-load detection.

    7. Restart the sequence for other half-bridges / full-bridges.

    Best,

    David