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DRV8841 design for 2A??

E Sheng Toh
Prodigy 20 points
Other Parts Discussed in Thread: DRV8841

Hi,

I am new in this field.. i am tasked to design a motor driver for robotics application. i have got the sample drv8841 for testing but found that i am able to drive until only 0.1A.

Is there any design consideration that i didnt put that is giving this results ?

I am driving 2 DC motor with a 3 cel lipo battery. Driving the circuit is using a 3.3v microcontroller with 10kHz PWM signal.

Lastly, i feel that the leads for the chip are too small to take up 2A per channel....

  • 0
    TI__Expert 7455 points

    Hi E Sheng Toh,

    DRV8841 can reliably drive up to 1.8A RMS (2.5A peak) if good enough heat sinking is provided. I think the reason you are only seeing 0.1A may be VREF is too small and hence the current chopping is getting engaged. It is highly recommended you take some time to understand the current chopping mechanism provided with this device. The datasheet has a good section on this topic, and if you go to the DRV8841 web page, you will see some application notes on current regulation as well.

    The pins are really not that small, so I would not feat for the device's life as long as it is not stressed beyond Abs Max. The bond wires inside the device are considerably smaller, but they are still rated to drive the current.

    Hope the info helps. Best regards,

    Jose Quinones

  • 0 in reply to Jose Quinones
    Prodigy 20 points

    hi jose,

    thank you for the prompt reply.. 

    I have changed the circuit to disable current chopping and hereby getting higher rating.. 

    The thing i am curious is that the input of the driver nReset and nSleep will draw larger current as the duty cycle increase ?

    sorry as i am still new in this field.

    The results i have from the test was current draw per motor up to 200mA before turn off when the nReset and nSleep was control by the Microcontroller...

    if i change the nReset and nSleep to fix voltage from the regulator of 3V, then i am able to reach 300mA per motor before turn off...

    Hope to receive your advise.

    thank you

  • 0 in reply to E Sheng Toh
    TI__Expert 7455 points

    Hi E Sheng Toh,

    It seems to me your microcontroller firmware is doing something to the nRESET and nSLEEP lines. These lines should be HI at all times while the device is under normal operation. If you are unadvertently toggling them, then the H Bridge will be disabled and possibly enter sleep mode in which case your load will not receive power from the batteries.

    I would look into what the nRESET and nSLEEP lines are doing.

    Best regards,

    Jose Quinones