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ADS1247 overload recovery time

ttd
Mastermind 8580 points
Other Parts Discussed in Thread: ADS1247

 

Dear Technical Support Team,

 

I have a question about ADS1247.

 

It has chopper-stabilized PGA.

Do you have an information of recovery time (unstable to stable) when it is driven from overload to non-overloaded state?

Dose it have relationship between overload of input voltage and recovery time?

 

For example,

100ms recovery time on 1V overload.

500ms recovery time on 2V overload.

100ms recovery time on any overload.

xx ms recovery time on 6.4V(100mV x Gain 64) overload.

 

■Condition

Input Voltage: 0mV ⇒100mV ⇒ 0mV ⇒100mV　・・・

Internal Reference： 2.048V

PGA: CASE1 ⇒ PGA 64(100mV x 64 = 6.4V ←It is overload over 2.048V)

  　 CASE2 ⇒ PGA 16(100mV x 16=1.6V ←It is not overload)

 

■Problem

Converted data shows below on 0mV.

Sometimes it shows around 3000 on PGA 64.

PGA 16 setting doesn't shows 3000(always shows around 300).

I guess it is caused by overload.

 

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Best Regards,

y.i

  • 0
    TI__Guru* 97465 points
    y.i.,



    I'll need to check further on this question. I believe that we have checked into the overload recovery time. It often comes up when multiple channels are used at different gains. Going from channel to channel will often require a specific configuration order so to that the PGA isn't overloaded.

    To my recollection, I believe that the PGA recovery may take about 2ms of wait time. Again, I'll need to check that, but in most data rates, it doesn't add much overhead to the data collection time.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Mastermind 8580 points
    Hi Joseph Wu,

    Thank you for your answer.
    If you prepare it , please let me know.

    Best Regars,
    y.i
  • 0 in reply to ttd
    TI__Guru* 97465 points
    y.i.,


    After discussing this with a colleague, the 2ms time for overload recovery is correct. We don't have any data overload magnitude and if it contributes more to the overload recovery.

    As I mentioned earlier, this is something that was discovered based on fast channel cycling and the amount of time required to set the PGA gain from one channel to the next. In cases where measurements from channel to channel may see large changes in gain and input magnitude, it is important to prevent the PGA from going into an overload condition (either in differential input, or output of the PGA into the rail.

    If the input is going from small input in gain, to a large input in lower gain, it is important to set the PGA first to the lower setting and then change the channel. If the input is going from a large input to a smaller input in gain, then it is important to set the channel first and then set the gain.


    Joseph Wu