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TM4C1294NCPDT GPIO drive strength

Gergely Bacso
Intellectual 545 points

Other Parts Discussed in Thread: TM4C1294NCPDT

Hi all,

As I know the maximum TM4C1294NCPDT GPIO drive strength is 12mA.
I want to connect a 15mA current sink to the GPIO of the MCU.

Can it damage the MCU or will the current be simply limited?
Anyone with some experience on that?

Thanks,
Gergely

  • 0
    Guru 27665 points
    Add a small signal FET or a 74LVC series buffer to buffer your output.

    A 15mA sink might work but isn't it worth a few pennies for reliability?

    Robert
  • 0
    Guru 47900 points

    Gergely Bacso said:
    I want to connect a 15mA current sink to the GPIO of the MCU.

    Not all "wants" are legitimate!    Should not you "govern" your wants to the needs/requirements of the MCU?

    As poster Robert states - using the MCU as a, "Beast of Burden" is never recommended.  

    Use of a component more suited (and sacrificial) to your power demands is very sound.

  • 0 in reply to Robert Adsett
    Intellectual 545 points

    Hi Robert,

    the current sinks are actually many LEDs and resistors. I will increase the resistance of the resistors on the next board (connected to the main board).
    I just wanted to know if I can execute tests safely with the current setup.

    Gergely

  • 0 in reply to Gergely Bacso
    Guru 27665 points
    If that's the case why not just change the resistors now? It's a simple enough operation.

    Even still there is something to be said for an external driver. Although if you keep with in the pin,port, side and chip limitations you should be fine.

    Robert
  • 0 in reply to Robert Adsett
    Guru 47900 points

    Robert Adsett said:
    if you keep with in the pin,port, side and chip limitations you should be fine.  

    I recall (similar) advice to (past) Titanic passengers: "If you keep to starboard side (of this sinking ship) align at/around rows 18-34, stand on one foot and don't lose your balance"  you too - should be fine...  

    Reducing the perceived brightness of any display - due to the "savings" of a proper (well suited) component - most always proves a mistake!

  • 0 in reply to Robert Adsett
    Intellectual 545 points
    Replacing the resistors on this assembled board by hand is (almost?) impossible. I surely can't do that.
    The side/chip limitations are kept, so I hope it will survive a few 15mA sinks...

    @cb1-: In the future, if the LEDs aren't bright enough, I will consider using an external driver.
  • 0 in reply to Gergely Bacso
    Guru 47900 points
    Good for you - really (I am IN the display & display control Biz) the brightness & clarity of the display HUGELY impacts product success! (I've many pro studies to support)

    If there is not sufficient margin to accommodate the (proper) components - you (likely) have priced your product incorrectly!
  • 0 in reply to Gergely Bacso
    Guru 27665 points
    You're the best judge of your capabilities but I've hand soldered below 0805 and I've not a particularly steady hand. I've seen a colleague do 0203 by hand but I wouldn't expect your parts to be that fine considering they are power dissipaters. The key is lots of flux.

    Robert
  • 0
    TI__Guru 59540 points
    Hello Gergely,

    Unfortunately, there are no assurances of device performance if you exceed the specified limits. Drawing too much current through the pin buffer could result in damage.

    With that said, on a very limited test scenario, it should work OK. In many cases there is margin on the capability or the capability is limited at one temperature extreme or the other. Even with this, it is a do at your own risk venture and it is not advised.