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MSP430F6636: Missing Supply Line to DVcc3

Fusillade
Prodigy 190 points

Part Number: MSP430F6636

We have +3.3V as well as a filtering cap attached to each DVccx pin (DVcc1, DVcc2, and DVcc3). After a recent board revision, a schematic trace was accidentally deleted. The result is that, while the filtering cap is still attached to DVcc3, the 3.3V is no longer attached. I read a post response from Jens-Michael in which indicates he recommends that power be applied to all pins. Can we get away with only having +3.3V attached to two of three MSP430F6636 Vcc pins for this board run (Rev 2 is in the works) or shall I go ahead and plan on having these boards reworked?

Thanks!

  • 0
    TI__Guru 71216 points

    Hello Fusillade,

    Jens-Michael is absolutely correct.  Pin DVCC3 must have +3.3v connected to it.   If this pin wasn't needed then the MSP430 wouldn't have it, so apparently it is required.

    If +3.3V is absent, some internal circuits may not be getting sufficient power to operate properly across the operating range of the device.  In other words, the device may work at room temp at 8MHz, but say at 20MHz, the device will fail to operate properly, or some may work and others may not, or it may work for a while, but those internal circuits that are not getting the +3.3v may begin to fail over time.  If so, that could result in a costly return or recall of your product. Why throw caution to the wind?  Do the rework or re-design the PCB. :)

  • 0 in reply to Dennis Lehman
    Prodigy 190 points

    Thanks for you reply.

    The first thing I did was measure +3.3V on the filter capacitor on Vcc3 and compare it to Vcc1 and Vcc2. Despite not being connected to +3.3V, the voltages were identical to the mV so I assumed they were connected internally; however, I thought I better ask to be sure since I'm not testing under full load or in extreme conditions and did not know how it would affect power distribution.

    New board is already in the works and I'll let production know about the necessary re-work. Good thing I'm heading out of town so I won't have to hear them cussing me. LOL

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