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INA186: Reduce power consumption when current measurement is not needed

Franz Schellhase
Expert 3605 points
Part Number: INA186

Hi team,

Can you answer the following customer inquiry, please?

The component has an ENABLE pin and a VS pin. When I don't need the current measurement and want to minimize the consumption, can I then switch ENABLE and VS both to GND or must VS remain energized while ENABLE = GND ?

Could I also use the 6-pin version without ENABLE and deactivate the component by VS = GND ?
Or would it cost more power in standby than if I use the 8-pin variant with the ENABLE ?

Thank you,

Franz

  • 0
    TI__Mastermind 27470 points

    Hi Franz,

    With ENABLE pin present, VS can but doesn’t have to be set to GND in order to shut down. It can be left energized.

    When ENABLE pin is not present, setting VS to GND shuts down the device equally well. It wouldn’t cost more power in standby. Rather it should cost less than with ENABLE pin. If you have the option of setting VS to GND, then you should be able to use the 6-pin version.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Intellectual 300 points

    Hi Guang,

    I'm the customer. Thank you for this information. I've designed my first version of the PCB for the 8-pin device, just to be more flexible.
    I'm going to test disabling by ENABLE = VS = 0 (I assume that's what equals the 6-pin) and by ENABLE = 0, VS = 1.

    If ENABLE = VS = 0 uses less current than ENABLE = 0, VS = 1, then I will go for the 6-pin in the final design.

    Can I ask why the 8-pin version with the ENABLE exists, when the 6-pin version can be disabled just as well ?

    Best regards,
    Martin

  • 0 in reply to Martin Schmidt93
    TI__Mastermind 27470 points

    Hi Martin,

    Welcome to use our forum. 

    One situation I can imagine is when the Vs source is shared by other devices. It may not be an option to simply shut off the supply itself. Instead you may want to selectively shut down some devices while keeping others alive. In this situation, an enable pin is handy.

    Another valid reason is startup time. It may take longer for a device to power on from 0V, but if an enable pin is present, the device can be made such that essential circuitry is selectively kept on therefore it responds faster when enable pin toggles. 

    These are what I can think of at this moment, there might be other scenarios.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Intellectual 300 points

    Hi Guang,

    my situation is as you say: I cannot turn off VS as it supplies essential power to other devices.
    But this is not a problem, as I can use the 6-pin variant and wire VS to an I/O of a microcontroller (INA186 just draws 90uA).
    Then I can use that I/O to turn on/off the power to the INA186. Am I missing something ? Will the absence of VS create additional currents from IN+ and IN- to GND ?

    Startup time can be an issue, I will test that when I have my board.

    Can you tell me where the ENABLE-pad of the chip is connecting in the 6-pin package ? Does it connect to the VS-pad ?

    Best regards,
    Martin

  • 0 in reply to Martin Schmidt93
    TI__Mastermind 27470 points

    Hi Martin,

    You can use IO to control the power to INA186. The absence of VS will not create additional current form IN+/- to GND.

    As a reference, you many refer to figures 17-19 in the datasheet for delays under a few scenarios. I don’t see a big difference in delay time between power supply startup and enable/disable.

    In the 6-pin package, the ENABLE pad is wire bonded to VS.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Intellectual 300 points

    Thank you Guang, this answers all my questions. I will start with the 8-pin variant in my eval board, do a few tests on in, then use the 6-pin for the actual product-PCB.

    Best regards,
    Martin

  • 0 in reply to Martin Schmidt93
    TI__Mastermind 27470 points

    Hi Martin,

    Glad you’re moving along with your project, please let us know in case you have further questions in the future.

    Regards, Guang