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DRV8243-Q1: nFAULT triggered after some sec

Pratik Acharya
Prodigy 50 points
Part Number: DRV8243-Q1
Other Parts Discussed in Thread: DRV8245-Q1

Hello,

When DRV8243 is driven up to 7.9A it is working fine as intended. but When it is driven  at 8A  load , the nFAULT is becoming active after some time(sec).

Can you please let me known why is this so .

Screenshots of schematic and scope is attached for reference.

  • 0
    TI__Mastermind 26455 points

    Hi Pratik,

    It appears you may be experiencing a TSD thermal shutdown due to junction temperature exceeding 155°C. This could happen pretty fast that you may not be able to measure the high temperature on the device. You could use this Full Bridge Driver Junction Temperature Estimator https://www.ti.com/tool/download/SLVRBI3 excel calculator to estimate die temperature with your operating conditions. If you find out that current is causing TSD you must switch over to either DRV8244H-Q1 or DRV8245-Q1. You can estimate the die temperature selecting these devices as well in the excel calculator. What is the supply voltage of your application? Did you compare the thermal performance using a TI EVM for the DRV8243H-Q1? 

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    Prodigy 50 points

    Supply voltage is 16V , but Iam using a programmable load box with constant current irrespective of voltage.I don't have DRV8243 EVM but i have estimated junction temperature with the TI graph.The graph shows for continous 8A at 50sec DRV junction temperature is 145 degree.

  • 0 in reply to Pratik Acharya
    TI__Mastermind 26455 points

    Hi Pratik,

    Thanks for the additional info. The TI graph is based on specific PCB dimensions and layers mentioned in the estimator. The thermal profile will be different with your PCB. Can you provide your PCB dimensions, layout information diagrams for all the layers and the cu oz used for each layer? 

    Regards, Murugavel