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TM4C123BH6ZRB: Maximum allowable GPIO current

Harini Madhusudhan
Prodigy 160 points
Part Number: TM4C123BH6ZRB

Hi,

I am having some trouble in figuring out the maximum GPIO current per output pin. I see that there are 2,4,8 mA drive mentioned in the GPIO section but in the electrical characteristics the maximum GPIO current per output pin is defined as 64mA. This maximum current also has a note that says not recommended for extended periods of operation. What would be the maximum current per GPIO pin for extended periods of operation? I would like to know this because I am trying to drive four or five solid state relays from TM4C123xxx or TM4c129xxx whichever is better current drive since both work for the rest of our application.

Thanks! 

  • 0
    TI__Guru*** 135355 points
    Hello Harini,

    The typical/recommended is the current draw configured by the GPIO settings. That should be considered the 'maximum over extended periods of operation'. The absolute maximum of 25mA for TM4C123x devices or 64mA for TM4C129x devices is tolerated for short amounts of time before potentially overstressing the device. Also keep in mind there are also limitations of current draw for entire sides of the device discussed in the "GPIO Current Restrictions" table within each device datasheet.

    For your application, it is NOT advised to drive solid state relays directly from MCU GPIO's! We have Relay Drivers that are designed to be the interface between an MCU and a solid state relay. Please look into these device offerings and learn about how to utilize them to meet your application needs.
  • 0 in reply to Ralph Jacobi
    Guru 117855 points

    Vendor's Ralph provides solid advice - the MCU is the "brain" of your system - and (rarely - if ever) should be relied upon to supply 'muscle.'

    Depending upon the voltage (or especially the current) levels being switched - it will prove much to your advantage to employ 'isolation' (usually opto or magnetic) so that such 'Power Switching' does not induce: 'Noise, Ground Bounce and/or other destructive transients' - which more often than not - may wreak havoc upon your system!

    Note too - what (appears) to be 'bullet-proof' w/in the 'Lab' - so often 'suffers' - when subjected to the 'less friendly' - real world!      Hope for the 'best' - yet 'plan/provide' for the worst...

  • 0 in reply to Ralph Jacobi
    Prodigy 160 points
    Thanks so much for the information. I was evaluating the option of using a relay driver too and now it totally makes sense to use a driver after the MCU.
  • 0 in reply to cb1_mobile
    Prodigy 160 points
    Thanks for the information.
  • 0 in reply to Harini Madhusudhan
    Guru 117855 points
    You should give good consideration to the location of any, Relay Drivers - too. (ideally place them (near) board's edge, and (far) from sensitive, low level analog signals and/or high-frequency/critical signals - which may be 'impacted' by the 'sudden & high current flow.)