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MSP-EXP430F5529LP: RXD powers 3.3V rail

rafael rodrigues
Prodigy 60 points

Part Number: MSP-EXP430F5529LP

My EXP430F5529LP rev1.6 is connected to an USB port on PC, the 3V3 and 5V jumpers are disconnected, and the RXD jumper shows 2.7V. The problem is I can measure 2.1V on the 3.3V power rail coming from RXD jumper. It's normal? I couldn't find useful information in the slau533d.pdf. I'm just affraid of having an unexpected behavior when plug other devices.

  • 0
    Guru 43865 points
    Yes, it is "normal" but opinions differ as to whether it is a "bad thing". You are powering the device via the ESD diodes connected to RXD. In my opinion, since putting a voltage on a pin exceeds the Absolute Maximum rating, it should be verboten.

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