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ADS8686S: ADS8686S implementation

Adam B.
Prodigy 30 points
Part Number: ADS8686S
Other Parts Discussed in Thread: ADS8568, ADS8556

Tool/software:

Hello,

I hope that you are doing well.

I was looking for a poly-meter for 3-phase 115v 400Hz grid measurement but couldn't find any.

I am searching for a simultaneaous 10 channels ADC to perform the Analog to Digital conversion at least and send the data to the CPU that will perform the measurement with the embedded DSP.

The 10 channels will be dedicated to 3 voltages measures (1 per phase) and 6 current measures (2 per phase).

The website seems to recommend the following reference for those simultaneous measurements "ADS8686S".

Can you please comfirm that this reference is OK for our application ?

Please don't hesitate to give me any suggestions regarding my request, you know better than I if you have any better alternative.

Regards,

Adam,

  • 0
    TI__Guru**** 181811 points

    Hi Adam,

    Doing well!  Thank you for asking!  The ADS8686S has two ADC cores internally, each fed by an eight channel MUX.  It is capable of simultaneously sampling 2 channels at a time by eight channel pairs.  Do you need to sample all 10 inputs at the same time?  Can I also ask why you need 10 channels for a 3-phase system?

  • 0 in reply to Tom Hendrick
    Prodigy 30 points

    Hello Tom,

    I need to sample the following : 3 phases voltage, 3 phases current on a socket A, 3 phases current on a socket B.

    The CPU shall compute the power factor so I need to measure, on each phase, 1 voltage and 2 currents.

    In order to compute the angle between each phase, I also need to measure all 3 phases simultaneously.

  • 0 in reply to Adam B.
    TI__Guru**** 181811 points

    Hi Adam,

    OK then, you need all channels to simultaneously sample, it sounds like the channel pair option of the ADS8686S won't fit your needs. 

    You might consider using two ADS8556 devices, which are 6CH, 16-bit converters.  These parts also work in channel pairs, but there are 6 ADC cores and they can all be sampled at the same time.  Channel pairs A, B and C are controlled via independent convert start pins which can simply be tied together - giving you the potential of sampling 12 channels all at the same time.  There is also the ADS8568, which has 8 channel pairs and four independent convert start inputs.