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ADS1274 Power sequence requirement?

Hak-Jin Jeong
Intellectual 350 points

Other Parts Discussed in Thread: ADS1274

Hello, I am using ADS1274 in my sensor interface module.

I think the nDRDY of ADS1274 should be changed periodically if powers(DVDD,IOVDD,AVDD) are properly provided to the ADC and if CLK is also properly provided,

but I found one problem in my sensor interface module.

When I turn power supply, sometimes nDRDY of ADC is not changed periodically and just it remains high.

In this case, If I do pwer-cycle(turn-off and on again), nDRDY starts work correctly.

CLK is always provided correctly in all cases.

In my sensor interface module

DVDD=1.8V

IOVDD=3.3V

AVDD=5V

and 5V AVDD is LDO regulator(TPS70950) output (7V input)

and 3.3V IOVDD is LDO regulator(TPS70933) output (5V AVDD input)

and 1.8V DVDDD is LDO regulator(TPS70918) output(3.3V IOVDD input)

so, consequently, AVDD is the first applied, IOVDD is the next applied , and DVDD  is the last applied.

Is there any requirement of power up sequence or power rising time requirement? or any other?

Please let me know your valuable recommendations/opinions about this issue.

Best Regads

Hak-Jin Jeong

  • 0
    TI__Mastermind 23235 points
    Hello Hak-Jin -
    The power supply sequence for the device is shown in Figure 84 of the datasheet. The most important is that AVDD comes up last; so this could be one of the reasons that you see random behavior in your circuit. Also take into account the differing amounts of decoupling capacitance on the supplies in terms of how they can affect the supply startup.