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ADS7263: AVDD and DVDD

Y.Ottey
Mastermind 6145 points
Part Number: ADS7263

Dear TI team,

I would like to ask following questions about AVDD and DVDD in ADS7263.

1. The ADS7263 requires two power supplies, AVDD and DVDD. When VDD and DVDD do not rise at the same time at power-on, which one needs to rise first?
(Or do you need to start AVDD and DVDD at the same time?)

2. If the power is turned on in the opposite order to the one asked in step 1, does it affect the operation?
(If you answered that you need to start AVDD and DVDD at the same time in question 1, what kind of effect will the operation have if they do not start at the same time?)

Best Reagards,

Y.Ottey

  • 0
    TI__Guru**** 160675 points

    Hi Y.Ottey,

    Usually the best way to see if a particular device has a power sequencing requirement (assuming its not specifically called out in the datasheet) is to look at the Absolute Maximum Ratings table.  Section 7.1 (pg. 6) for the ADS7263, the second entry on that table shows "Supply voltage, DVDD to AVDD".  There is a MAX limit and a note (2).  The MAX limit is 1.2 x AVDD.  So what this entry is telling us is:

    1. AVDD can rise up first, followed anytime by DVDD.
    2. AVDD and DVDD can rise together
    3. DVDD can rise ahead of AVDD by a factor of 1.2

    Do let us know if you have any further questions!

  • 0 in reply to Tom Hendrick
    Mastermind 6145 points

    Dear Tom

    Thank you for your reply.

    I would like to ask following adding question.

    If DVDD rises before AVDD and the voltage of DVDD exceeds AVDD × 1.2,

    is it OK to recognize that it will cause damage or abnormal operation because it exceeds the rating of DVDD?

    Regards,

    Y.Ottey

  • 0 in reply to Y.Ottey
    TI__Guru**** 160675 points

    Hi Yu,

    As long as you don't exceed the maximum current ratings, you shouldn't damage the part.  If you find the serial communications is not working, a software reset should restore normal operation, however it is best to try and drive AVDD and DVDD up together or bring up AVDD ahead of DVDD.