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DRV8806: Current Limits

Part Number: DRV8806
Other Parts Discussed in Thread: DRV777

Hello;

Is it possible to draw more current by using two DRV8806 in parallel connection ?

If it's not possible, we think that we can use DRV8806 as a gate driver for external MOSFET's. Thus, the main current doesn't flow through the DRV8806. Is there any objection regarding to use it in this way ?

Thanks in Advance 

  • Hi Sercan,

    It is possible to connect the outputs in parallel, but there are still power limitations.

    What is the desired current you seek?
    Do you need a VCLAMP pin?
    Do you need the serial interface?

    We may other devices that are better suited for your application.

    The DRV8806 with external circuitry can be used as a gate driver, but again there may be better devices such as the DRV777.

  • Hi Mr Duncan;

    Actually we're looking for a solution that we can draw at least 1.5A  (when all channels on). DRV8806 datasheet says that max 1A continuous output current can be drawn with adequate pcb heatsinking at 25°C.

    Could you please explain the power limitations when we connect the outputs of two DRV8806 in parallel ? What will be the approximate max current that we can draw in this situation ?

    Out other concern is an ambient temperature increase. We are not sure that we can still draw 1A when the ambient temperature reaches the 70-80°C.

     

    By the way, we dont need a VCLAMP pin and have to serial interface.

    DRV777 datasheet says that max 1A current can be drawn when all output pins are connected in parallel. Therefore, it's not possible to use it as well.

    Thanks.

  • Hi Sercan,

    Could you please explain the power limitations when we connect the outputs of two DRV8806 in parallel ? What will be the approximate max current that we can draw in this situation ?


    Placing two outputs in parallel does not provide double the current. It provides ~2.8A.

    This is because the power rating of the device sets the total current.

    So if the device can operate 2A through 1 FET, it can operate:

    1.4A through each of two FETs in parallel, total of 2.8A
    1.15A through each of three FETs in parallel, total of 3.45A
    1A through each of four FETs in parallel, total of 4A

    The I squared * R power calculation works out to approximately the same power in each of the above cases.

    Out other concern is an ambient temperature increase. We are not sure that we can still draw 1A when the ambient temperature reaches the 70-80°C.

    A rough calculation is that two outputs in parallel can provide up to 1.1A per output (total of 2.2A) at 80C.

    Please note these values are all based on the datasheet thermal information. Your board design will have a large impact.

  • Hello Rick;

    I think, you explained that the situation which two different outputs of the same IC are connected in parallel.

    I asked that situation which two different IC's outputs are connected in parallel. Could you please evaluate in this way ?

    Regards

  • Hi Sercan,

    Sorry, I missed that detail.

    Using two ICs should work, as long as you control the output switching using the LATCH.

    Write the SPI command to the two ICs, and when ready set the LATCH command on both ICs at the same time.