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MSP430FR6979 CONTROLLER DESIGN ISSUE

Other Parts Discussed in Thread: MSP430FR6979

Hi Ti Members

We are selecting MSP430FR6979 for our project.But we are facing some design challenges which are following:-

1) We are using 50th no. pin (P1.1/TA0.2/TA1CLK/COUT/A1/C1/VREF+/VeREF+) as a VeREF+ and given 2.5 V externally so how much value of capacitor we have to put on this power rail and why?

2) Some pins we are not using (like some GPIO's) then what will we do with this pin in our design.

  • Hi,

    Can anybody help on above question as we have stuck at these point for our design.
  • Hi Jasbeer!

    Both answers can be found in the User's Guide:

    JASBEER SINGH said:
    1) We are using 50th no. pin (P1.1/TA0.2/TA1CLK/COUT/A1/C1/VREF+/VeREF+) as a VeREF+ and given 2.5 V externally so how much value of capacitor we have to put on this power rail and why?

    JASBEER SINGH said:
    2) Some pins we are not using (like some GPIO's) then what will we do with this pin in our design.

    Dennis

  •  Hi Dennis

    Thanks for your reply.

    I,m not getting the VIH level of GPIO for this controller.

    In datasheet i have looked into Digital input section which is attached.-

    But in that attached image if we will treat VIT+ as VIH at 3 V then the max. value they have given as 2.25 which as per our understanding should be VCC if it is VIH state of GPIO.

    Please let me clear this issue.

  • The voltage threshold (i.e., where the input switches from "low" to "high") is guaranteed to be somewhere between 1.65 V and 2.25 V. So in the worst case, your signal must have at least 2.25 V to be received as "high". In any case, higher voltages work too (and do not waste as much power).

  • Sorry I do not understand what you have written.

    Unused pins (GPIOs) shall not be left floating. Therefore you can tie them externally to GND or Vcc, enable the internal pull-up/down resistor (or use an external one) or configure them to be outputs and set them to either high or low.

    VIT+ is the minimum threshold voltage for being detected as a high input. Your table says, that at 3V Vcc you would need 2.25V at the input so the MSP detects a high level in the worst case. But this does not really have something to do with the unused pins. Only that if you wanted to externally set them to high, you would need a minimum of 2.25V.

    Dennis
  • Suppose you need to buy something in cash, and you know that thing will cost at least $5 minimum and at most $10 maximum, now how much cash should you bring to be sure you can buy it?

    You should bring at least $10 minimum (and preferably more).

    The maximum it requires is the minimum you have to be prepared for. Otherwise you may be short.

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