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MSP430 VCORE, V18, and VUSB

Sinoj B S
Intellectual 540 points

Hi,

We are using  MSP430F5529IPN in our product. During production testing of the product PCB assembly we are planning to measure VCORE, V18, and VUSB pins of the uC using ADC. In the datasheet it has been indicated that "No external current loading is possible"  for VCORE and V18.

Will it affect the functioning of the uC even if I introuduce a high input impedance stage b/w VCORE or V18 pin and the ADC input? If it will really affect the uC functionality, has there a way to measure or verify that the internal of the uC is working fine?

Any help is appreciated.

Sinoj | INDIA

 

  • 0
    TI__Genius 14940 points

    The statement in effect is to indicate no power is deliverable from these pins.  It shouldn't be a problem to detect the voltage on these pins using a high impedance probe.  The concern is what is left after production testing.  Additional trace from these pins to a test point could modify the capacitance seen by the regulators and impact stability or degrade the performance if any noise is picked up here.  It would be a good idea to put a relatively high value resistor (5k to 10k) in series with the pin and have it mounted as close to the pin as possible to minimize these effects.

    Jim Noxon

     

  • 0 in reply to Jim Noxon
    Intellectual 540 points

    Thanks Jim.

    We are planning to take these measurements prior to downloading the firmware into the uC flash, as a voltage check. This will work out right?

    Sinoj B S

  • 0 in reply to Sinoj B S
    TI__Genius 14940 points

    I don't see any issues with what you are planning on doing.

    Jim Noxon

     

  • 0 in reply to Sinoj B S
    Guru 227245 points

    VCore may change depending on the firmware. If the firmware configures the MSP for low speed/low current or high speed/high current, VCore is adjusted accordingly. So checking it without the firmware loaded will only give you the default setting. If this is okay for you, fine.
    You shouldn't however, add too much wire (or a test pad) to the VCore pin. Best case you directly test on the capacitor. (give it a larger pad if you must)

  • 0 in reply to Jens-Michael Gross
    Intellectual 540 points

    Thanks for the comments. I will consider these steps in design.

    Sinoj B S

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