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Does F28335 has a pull down resistor ??

khaled maher
Prodigy 90 points


Hi

I know that Each pin of F28335 has a pull-up resistor. And I know how to enable or disable it.

But my question is that  are  there also a pull-down resistor attached to each pin??

Another question, What is the max current which any pin can sink or source ?? In the F28335 data manual (Literature Number: SPRS439A), there are 2 different values for the max current, one in the range of 4:8 mA and the other in the range of  80:190 micro ampere !!!

Thank you

  • 0
    TI__Guru** 119680 points

    only some pins have pullups or pulldowns. these are all noted in the pin description section.

    Table 6.2 shows max source and sink of either -4 to 4 mA or -8 to 8mA depending on group 1 or group 2 pins

     

  • 0 in reply to ChrisClearman
    Prodigy 90 points

    1) I think all GPIO pins have a pull up resistor only, as there is only a "pull up resistor disable PUD" registers which could be used for enabling/disabling these resistors. but there is no such a register for the pull down resistors.

     

    2) In table 6.3 there is another value ranging between 80:190 micro Amp, should I ignore it??

     

    Thank you





  • 0 in reply to khaled maher
    Guru 23000 points

    Hallo Chris,

    I can’t find a ‘pin description section’ in the Data Manual. Can you tell me where to find in which document on which page number?

     

    Hallo Khaled,

    The currents 80/190uA is the current trough the Pull-up/down resistors.

    Be aware: that normally a device has a maximum device current. Which means a single pin may be able to handle 8mA but when you use 16 pins at 8mA, total 128mA trough the device, it’s possible you will blow up the device. I can’t find this device current limit in the documentation.

     

    -Leo

  • 0 in reply to Leo Bosch
    TI__Guru** 119680 points

     

    6.2 is what you should ensure in your design, it shows the active source/sink current for a given pin

    6.3 is how the device will behave when conditions in 6.2 are met, the numbers are leakage current

     

    Leo,

    sec 2.2


     

  • 0 in reply to ChrisClearman
    Guru 23000 points

    Hi Chris,

    Section 2.2 is the Signal Description which briefly (not exact)  describes the pull-up’s but is not the full Pin Description as used in other device documents, which gives a clear module overview on Pull-up/down’s. This document himself refers to a Pin Description Section but there is non!

     

    -Leo

     

     

     

  • 0 in reply to Leo Bosch
    TI__Guru** 119680 points

    Leo,

    Table 2.2 (F281x) and Table 2.3 (F2833x/23x) are very similar in what they cover. For 2.3 we simply took out the PU/PD column and made a statement:

    All GPIO pins are I/O/Z and have an internal pullup, which can be selectively enabled/disabled on a per-pin basis. This feature only applies to the GPIO pins. The pullups on GPIO0–GPIO11 pins are not enabled at reset. The pullups on GPIO12–GPIO87 are enabled upon reset.

    There are only a few non-GPIO pins with PU/PD, and these are noted with a directional arrow.

    Both datasheets refer to a pin description section (in sec 6.7 and 6.5 respectively), and this refers to Table 2.2 / 2.3 for each document.

    Both also have identical electrical specs in 6.3 except for the F281x EVAB/GPIOB.