• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 101 subscribers
  • Views 1506 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AM335x ADC Errata Advisory 1.0.32

RY9983
Guru 10570 points


Hello,
I have a question about Advisory 1.0.32 in AM335x.(sprz360f)

I am wondering the operation when following conditions occured simultaneously.
  a) VDDA_ADC and AIN0 are connected, in AMUX5:1.
  b) VSSA_ADC and AIN1 are connected, in AMUX4:1.
  c) AIN0 and AIN1 are connected, in AMUX9:1.

If it occured, VDDA_ADC current flow into VSSA_ADC.
But, workaround does not say about this condition.

Q)
 - Does this condition NOT occur in ADC?
 - Is this condition NO problem in ADC?

Best regards, RY

 

  • 0
    TI__Guru**** 393215 points
    Will escalate this to the factory team for explanation.
  • 0 in reply to Biser Gatchev-XID
    TI__Guru 60865 points

    Yes this is possible.  However, the resistance of the internal analog switches will limit the current to a level that will not damage AM335x.  That is why you only need to add external resistors which limit current to attached devices,

    Regards,
    Paul

  • 0 in reply to peaves
    Intellectual 580 points
    I have a custom board where VDDA_ADC is supplied by a reference voltage source (LM4132-1.8). VREFP is connected to VDDA_ADC with a resistor (50 ohms) and VREFN is connected to VSSA_ADC. Nothing else is connected to this reference voltage. All analog inputs are equipped with 1k series resistors.
    During production test voltages are measured and on some units I can see a significant drop of the 1.8V voltage due to the parasitic current path described here, as long as core voltage is not present. The current that flows into VDDA_ADC is in the range 50mA-70mA on some units, exceeding the maximum current ratings of the data sheet (table 5-10), which is 10mA only for VDDA_ADC.
    My concern is about failure rate and part stress due to this current.
    Is there any specification on this current level during power up sequencing?

    Regards, Tom