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ADS7953: ADS7953SBDBTG4

RANGA SWAMY K
Intellectual 520 points
Part Number: ADS7953

Hi,

I am using ADS7953SBDBTG4 in my current project, I need clarification on "Power-up time" requirement Power Supply rail (We are using 5V analog supply in our design). As per the datasheet maximum "Power-up time"  requirement is 1 us which is pretty fast and I believe most of LDOs or DC-DC converter doesn't support to meet the "Power-up time"  requirement. Could you please confirm whether 1us "Power-up time" is same as ramp up voltage of the power rail?

is it fine to use 4.096V for Reference voltage? Absolute max value for REFP is not mentioned in datasheet. Please kindly advise.

Regards

Ranga

  • 0
    TI__Mastermind 36170 points

    Hello Ranga,

    The 'Power-up Time' in the datasheet does not refer to the ramp rate for the analog and digital supplies.  The power-up time, 1uS, is the delay from the time the supply rails ramp up to a valid voltage level (2.7<=+VA<=5.25), and when device IO communications can be begin.

    Using a standard LDO is preferred for low noise, but a good low noise DC-DC can also be used.

    The maximum Reference voltage is 3V; the device will not operate correctly with a reference voltage greater than 3V.  For ABS MAX specs, treat Vref inputs same as AINP, -0.3V(Min) to +VA+0.3V(Max).

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Intellectual 520 points

    Hello Keith Nicholas,

    Thank You Very Much for detailed explanation, could you please share what is the minimum ramp up time requirement for power rail? I couldn't find this requirement in datasheet.

    Regards

    Ranga

  • 0 in reply to RANGA SWAMY K
    TI__Mastermind 36170 points

    Hello Ranga,

    We do not have a strict power-up or down sequence, or a ramp rate for these devices.  However, once powered up, VBD should be equal or less than +VA.

    Also, in general for ADC's, it is important that the power-up ramp is monotonic for the power-up reset circuit to work correctly.  If your power-up ramp is extremely slow with a small amount of noise that could allow the voltage to move up and down, this could cause problems.  In general, a standard LDO or DC/DC that ramps in a few mS should not cause any isssues.

    Regards,
    Keith

  • 0 in reply to Keith Nicholas
    Intellectual 520 points

    Hello Keith,

    Thank You So Much for clear explanation.

    Regards

    Ranga