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LaunchPad MSP430G2553 vcc pin max amps

user4482941
Prodigy 10 points


I am using the LaunchPad to build a project to run some LED's. I was wondering what the max number I could run from the output pins without burning up the chip. ( I have seen the MAX the chip can output is 20mA across all pins. Mainly just want to verify that) I am also interested in how many milliamps the VCC pin can provide. 

Thanks,

Joey

  • 0
    Guru 74080 points
    The Vcc pin is an input and sinks current - the MSP is powered through this pin. For the outputs: in the datasheet you can see a graph that shows the voltage drop at the pins depending on the current they supply. The higher the current, the lower is the voltage which might get unusable at some point. The clamping diodes at the pins have a maximum current of 2mA, I guess - they will burn if overrated.

    Dennis
  • 0 in reply to Dennis Eichmann
    Guru 46710 points
    Well, from current point of view VCC pin is input (sink) but it is not input pin of the microcontroller, does not contain any clamping diodes as well. Certainly it's current handling capacity exceeds that of any other (I/O) pin. Also clamping diode current rating does not relate to pin current sinking/sourcing capability which exceeds 2mA. I looked into datasheet and shall admit that unfortunately did not manage to find maximum allowed current for VCC pin, nor maximum allowed dissipation of the chip. Hopefully TI representative can elaborate.
  • 0
    Guru 317480 points

    I do not know where you got the 20 mA from, but the absolute maximum ratings are where the chip can break immediately, so you should stay far away from those values.

    The clamping diodes do not matter because your circuit will not exceed the allowed voltages.

    As the "Outputs" specification in the datasheet shows, you must not exceed 48 mA for all pins if you do not want to have more than the specified voltage drop. You can use higher currents if you can work with higher voltage drops, but that's unlikely because with an unspecified voltage drop, you will be unable to correctly size the current limiting resistors for your LEDs.

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