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MSP430F2272: MSP430F2272 - Internal power connection

Sunset
Genius 14175 points

Part Number: MSP430F2272

Hello Team,

I'm supporting a situation where a product based on the MSP430F2272 got released in the market but the AVss got not connected.

The team is working on doing a redesign to make sure that the problem is solved. The system is properly working but they want to better understand the failing scenarios in the field, so they have asked how the internal power supply pins are connected.

In particular the ADC is working even if the AVcc is not connected beside the AVss (also not connected).

As failing scenario/problem I do see the following:

  • Without a good ground connection the analog peripheral may not get the specified datasheet values and are working out of specification (while they may be functional).
  • The internal ESD diodes may not be properly working and the IO might get some over stress.
  • 0.3V over Avcc or below AVss do not apply any longer since the ESD may not work properly.

Can you confirm the internal connection and failing scenarios?

Thanks,

SunSet

  • 0
    TI__Guru 56685 points
    SunSet,

    Biggest concern would be noise into the ADC here and improper ADC functionality. That being said, i'll have to check into this further, which could take some time.
  • 0 in reply to Jace H
    TI__Genius 14175 points
    Hello Jace,

    thanks for the follow up.

    Yes, you are right, the noise might be a concern.
    In general if the internal ground connection is not low impedance, I would assume that also the other parameters, such as SFDR, THD will degrades.

    I'm looking forward the update on the internal connections.

    Regards,

    SunSet
  • 0 in reply to Sunset
    TI__Guru 56685 points
    Sunset,

    AVSS and DVSS are not connected internally. It is thus imperative for AVSS to be terminated correctly for proper operation of the analog portion of the device. We cannot confirm what the failure cases are is you do not terminate AVSS properly as that scenario has not been tested.
  • 0 in reply to Jace H
    TI__Genius 14175 points
    Hello Jace,

    the customer is working on the PCB redesign but they need to make a risk analysis. While the Avss and DVss are not connected things are working. They made a measure on a the pins and they measure 16ohm and a voltage of ~0.25V. This sounds that the connection between the two pins is made internally via the ESD diodes, thus things are working.

    This connection is clearly not a valid and robust one, since one pin is floating and subject to noise that may easily break the connection.
    To better understand if what they are seeing is related to the ESD diode they have asked if we can share the ESD scheme and connection among the AVss and DVss.

    Thanks,
    SunSet
  • 0 in reply to Sunset
    TI__Guru 56685 points
    Sunset,

    Unfortunately, the internal structure of the chip beyond what is shown in the datasheet , is something we cannot share at this time.

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