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MSP430-2272 output power

James Russo
Prodigy 10 points

Other Parts Discussed in Thread: MSP430F2274

I need to get a minimum of 3.7V to the I/O pins to run sensors and an LCD screen and the maximum I am getting out of them now is 3.6. I was looking at the spec sheet and saw that the MSP430 has internal op amps which can adjust the gain to certain levels. My question is...does the op amp increase the voltage to the I/O pins so I can get the correct voltage to use the sensors or is it just an internal amplification?

  • 0
    TI__Guru 64920 points

    The supply voltage to the integrated op amp has a maximum of 3.6V as indicated in the datasheet of the MSP430F2274.

    The output voltage can not go any higher.

    In order to interface to devices with a different voltage requirement, level translation devices will be needed.

  • 0 in reply to BrandonAzbell
    Guru 227245 points

    There are soem tricks where you can raise the output voltage above the maximum output voltage of the MSP port pins. If done carefully, you're not damaging the processor. But you must carefully calculate the currents and consider any possible glitches.

    The MSP port have a clamp diode that will protect the ports agains overvoltage. These diodes can route up to 2 mA from the port to VCC. While doing so, teh voltage at the port raises another 0.2V. Also, you can put another diode (Schottky) in the line from the external device to the MSP. On this diode, another 0.2V will be piled up. Then place a pullup on the external devices side with a properly calculated value so that the line will reach <4V while the pullup does not source more than a few 100 µA.

    This way, if the MSP port is set to high, the external device will see up to 4V, and when the MSP is low, the line on the external side will be 0.2V higher than what the MSP can sink.

    Keep in mind that the current rushing into the MSP port pin will be float into VCC. So if your circuit draws less current from VCC than what rushes in, your 3.6V will raise, since most voltage regulators only limit the inrushing current from the power source, but cannot sink any excess current added to their output.

    You can, however, also use a transistor (e.g. FET) at the output, together with a pulldown and a reversed logic on MSP side.

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