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ADS1298R: Question about time settle in acquisition.

Pablo Sebastian Parodi
Prodigy 140 points
Part Number: ADS1298R
Other Parts Discussed in Thread: ADS1298

Hello. I'm working in a project with the ADS1298. I need some help to understand something about the data rate and time settle:

If im trying to have a 500 SPS (24+24*8 bits ready to be taken by spi, every 2ms), so DRDY should toggle to 0 every 2ms...when I see the t settle table

in the datasheet ( p. 51) it shows a time settle (when DRDY should toggle to 0 to indicate new data) of 18440/2048000 = 9ms...that is a data rate of 111 SPS

So thats my confusion...which is the correct data rate (I understand data rate as have the 24+24*8 bits ready)? 500 sps or 111 sps?

Thank you. 

  • 0
    TI__Guru 66166 points
    Hi Pablo,

    Thanks for your post.

    The settling time is different than the data rate period. When the START pin is taken high, or the START command is sent, the modulator will begin sampling the input. It takes some time for the digital filter to settle and output a valid result. The /DRDY pin is held high and the unsettled data is hidden from the user. After the settling time is complete, the modulator will continue converting and a new sample will be available to read at the set data rate (i.e. 500 SPS).

    Best Regards,
  • 0 in reply to Ryan Andrews
    Prodigy 140 points
    Hello Ryan. I was able to get an oscilloscope, and this morning saw exactly what you said. The settle time occurs only at the beggining of convertion and, if I understood well, it is the neccesary time to do the intial calculations at the filter. Then, as the filter is full of data, the output would be able to deliver data at the requested data rate.

    Thank you