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DRV8244-Q1: DRV8244 Output Pin Connected together to Increase Current Capability

Bing Li
Prodigy 50 points
Part Number: DRV8244-Q1

Tool/software:

Hello Colleague

In my application, I need a half-bridge driver to control external lock motor. The feature of the lock motor is normal current 5.5A(@200ms) and stall current 15A(@500ms). 

I would like to use the part of DRV8244, and have below questions for your support

1. Does the output pin of DRV8244 connect together to increase the current capability? I just need a half bridge with bigger load current.

2. If it can be used with the output pin connected together, how is the current capability? Can it handle the lock motor which I raised above?

3. If it can not be used as above, what's your proposal to drive such lock motor?

Thanks

  • 0
    TI__Mastermind 24530 points

    Hello Bing,

    Bing Li said:
    1. Does the output pin of DRV8244 connect together to increase the current capability? I just need a half bridge with bigger load current.

    While this can be done I would recommend taking a look at the DRV8144 for a better solution. If you need more current capability than the DRV8144 can supply I would recommend taking a look at the DRV8145 instead.

    Bing Li said:
    2. If it can be used with the output pin connected together, how is the current capability? Can it handle the lock motor which I raised above?

    The DRV8144 can support 17.5A for 1s so this should be able to handle the lock condition. If you would like to be sure based on your system requirements, you can check the thermal capability of our DRV814x-Q1 half-bridge drivers using our half-bridge junction calaulator: www.ti.com/.../SLVRBN2

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 50 points

    Right now, I need to evaluate all the solutions for the new function. 

    1. I get your confirmation that the DRV8244 can be used as a half bridge with the 2 output pin connection to increase the current capability. May I know whether it can handle the lock motor(Nom. 5.5A@200ms; Stall 15A@500ms)? Is there any points need to take care in the design? Please share your comments.

    2. For the part DRV8144, I already asked the local TI colleague to check the price. Btw, I use the "Junction Temp Estimator" to evaluate the thermal performance, but I found the

        a. "Slew Rate" and "VM" impact nothing on the thermal result

        b. For PCB list, I select the bigger PCB size(8cm x 4cm) with the worse thermal result, but smaller PCB size(2cm x 2cm) with better result. May I know the reason?

  • 0 in reply to Bing Li
    TI__Mastermind 24530 points

    Hi Bing,

    Let me double check if the DRV8244 can be used in parallel mode, there is a chance that the thermal performance can be worse than the DRV8144 since one OUTx may turn on before the other one does even if IN1 and IN2 are tied together.

    Bing Li said:
        a. "Slew Rate" and "VM" impact nothing on the thermal result

    This is because only the high-side FET is being taken into account. The equations used in the calculator are in this app note: https://www.ti.com/lit/an/slva504a/slva504a.pdf

    So to let SR and VM have an effect, the current input needs to be set as a negative value:

    Bing Li said:
    b. For PCB list, I select the bigger PCB size(8cm x 4cm) with the worse thermal result, but smaller PCB size(2cm x 2cm) with better result. May I know the reason?

    This seems to be only with the positive current, I am not too sure why this appears to be the case that the smaller PCB size has a slightly better performance. The calculators works off of foster networks so something in there is causing this, but using negative current, the thermal performance is as expected with the larger PCB having better thermal performance.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    TI__Mastermind 24530 points

    Hi Bing,

    I checked if the DRV8244-Q1 can be used in parallel mode, it cannot. The DRV8244 will have issues when the OUTx pins are tied together. For higher current capability either the DRV8144 or DRV8145 devices will have to be used.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 50 points

    Hello Cruz

    The issue to tied OUTx together is the current balance issue when the output have a shortage failure, right? DRV8244 is the dual channel of half-bridge. The 2 half-bridges may have the good consistency in one package. So, even this it still can not be used in parallel, right?

  • 0 in reply to Bing Li
    TI__Mastermind 24530 points

    Hi Bing,

    What you said is correct. Since the DRV8244 does not have a parallel mode, one high-side FET may turn on before the other due to propagation delay differences within the device itself leading to a OCP fault or TSD fault. This is why the DRV8244 is not recommended for parallel output.

    In devices which support paralleled outputs, we will have a parallel mode available. This parallel mode changes how the signals to the gate driver are sent so that the paralleled half bridges are provided the same signal internally to prevent differences in propagation delay from allowing shoot through conditions or one FET from turning on before another which will lead to the current balance issue which can cause OCP or TSD to trigger.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 50 points

    Thanks for your great support on this topic. 

    I will use the part DRV8143 in my design to drive the release motor.

  • 0 in reply to Bing Li
    TI__Mastermind 24530 points

    That's awesome! Please let us know if you need any further support!

    Regards,

    Joshua