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AM335x GPIO drive strength

g.f.
Guru 15520 points

Hi,

I have a question about AM335x GPIO drive strength.

I would like to know the total value of the current
which can be driven by using all the GPIO pins.

In AM335x datasheet(sprs717f) page.93 Table 3-13,
it seem that drive strength is 6mA for "All other LVCMOS pins" which include GPIO.

AM335x has 114 GPIO pins and each pin's drive strength is 6mA,
so that if using all GPIO, the total current which GPIO can drive is 114 * 6mA = 684mA.
Is this understanding correct?

best regards,
g.f.

  • 0
    TI__Guru**** 393215 points
    Not entirely correct. "All other LVCMOS pins" do not include all of the GPIO's. There are GPIO's muxed behind other signals listed on previous pages in the same table, which have 4mA drive strength.
  • 0 in reply to Biser Gatchev-XID
    Guru 15520 points

    Hi Biser,

    Thank you for the quick reply.

    I checked the datasheet Table 2-7 and please let me ask again.
    In Buffer Strength(mA) part, I found the pins which drive strength is 4mA.
    There are 14 pins(multiplex with GPIO) which drive strength are 4mA.
    If using these pins as GPIO, the drive strengh is not 6mA but 4mA.
    So, the total current is (100 pin * 6mA) + ( 14 pin * 4mA) = 656mA.
    Is this currect?

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru**** 393215 points
    Yes, this would be the maximum current if all pins are switched to output and driving at max. current. What is the purpose of this question?
  • 0 in reply to Biser Gatchev-XID
    Guru 15520 points

    Hi Biser,

    Thank you so much.
    Now, I'm cleared.

    This question was from my customer.
    They just wanted to know the total current which GPIO pins can apply.

    best regards,
    g.f.

  • 0 in reply to Biser Gatchev-XID
    Guru 15520 points

    Hi Biser,

    I'm sorry but let me ask one more question.

    In the datasheet page.86 there is table for Maximum current.
    The total max current of VDDSHV1 - VDDSHV6 are 350mA.
    GPIO total current value(656mA) which I calculated exceed this max current.
    So, do I need to consider the max current(need to be less than 350mA)?

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru**** 393215 points
    g.f,
     
    I find your customers initial question as quite meaningless, as I can think of no use case which will require all GPIOs switched to output and loaded to maximum possible current. However, tell them that Table 3-10 suprecedes Table 3-13. The maximum load current in Table 3-13 (4-6mA) is the condition under which the output voltage levels are measured.
  • 0 in reply to Biser Gatchev-XID
    TI__Guru 63125 points

    I assume the customer understands AM335x GPIOs are multiplexed with the other peripheral interfaces and the number of GPIOs available will depend on how many of these peripherals are required.  Most applications require several high-pin count peripherals that consume many of terminals which can also be used as GPIO.  Therefore, it is very rare to find an application that can use a majority of the GPIOs.

    We need to understand what they plan to connect to the GPIOs before we can provide a better answer to their question.

    Please ask the customer to provide more details related to their motivation for asking this question.

    Regards,
    Paul

  • 0 in reply to peaves
    Guru 15520 points

    Hi Biser and Paul,

    Thank you so much for the answer.
    And I'm sorry for asking such question.
    I understood and I will ask my customer.

    best regards,
    g.f.