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DRV8711: Current through AOUT1, AOUT2, BOUT1, BOUT2

Shota Mago
Expert 8120 points
Part Number: DRV8711

Hi team,

Could you let me know how much current will through  for each AOUT1, AOUT2, BOUT1 and BOUT2?

Or could you provide each impedance value?

Best regards,

Shota Mago

  • 0
    TI__Guru 56650 points

    Shota,

    The output drive current capability are provided in the spec table.

  • 0 in reply to Wang5577
    TI__Expert 8120 points

    Hi Wang-san

    Thanks for quick reply.

    But my customer would like to know current flow in/out at terminal AOUT1, AOUT2, BOUT1, BOUT2.

    Not gate driver sink/source current such as A1HS, A1LS, A2HS, A2LS, B1HS, B1HS, B2HS, B2LS.

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru 56650 points

    Shota,

    When high side FETs are turned on, the gate drive current goes out from xxHS and returns back from xOUTx. For example: the gate drive goes out from A1HS and return back from AOUT1. The A1HS gate drive current is same as AOUT1's current.

  • 0 in reply to Wang5577
    TI__Expert 8120 points

    Hi Wang-san

    Let me clarify your answer.

    I thought gate drive current flow into VM or source of FET.

    But this is not correct, actually xOUTx terminal is just not only for monitoring inductance voltage but also sink/source current as much as gate drive current.

    Is this understanding right?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru 56650 points

    Correct. According to Kirchhoff current laws, flowing into the FET's gate current is equal to the flowing out current (back to xOUT pin).

  • 0 in reply to Wang5577
    TI__Expert 8120 points

    Hi Wang-san

    Thanks for your quick reply.

    Although I think it's basic question, would it be possible to how did you derive xOUTx current = gate drive current?

    Additionally, could you let me know resistor value which is connected to each xOUTx node to GND as shown in Figure.15?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru 56650 points

    Shota,

    Kirchhoff laws: (https://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws)

    For a joint, flowing in current is equal to flowing out current. According to this principle, if you circling a circuit, the flowing in current should be equal to flowing out current.

    So, xOUTx current = gate drive current unless you find other current leakage path. Yes. You can argue the Cgd current vs Cgs current during FET turn-on/off transient. That can make xOUTx current is different than gate drive current. In this case, you have to measure it.  "xOUTx current = gate drive current" just gives you an xOUTx current estimation.