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ADS8568: High resolution, phase compensated simultaneous sampled inputs

gary mella
Intellectual 440 points

Part Number: ADS8568
Other Parts Discussed in Thread: ADS8584S, ADS8588S, ADS8578S

I have an application, where I need to sample 4 inputs simultaneously (range +/-3V RMS, 50 Hz signal). I require minimum 13 bit resolution and no phase delay between channels. I would like to know the suitability of ADS8568 before prototyping. 

  • 0
    TI__Mastermind 25070 points

    Hello,

    The ADS8568 is a great choice.

    I also went ahead and did a quick parametric search based on the criteria you provided to see what other choices there are, and came out with 8 parts, the ADS8568 being one of them. I will point out that the ADS8584S is a 4 channel device.

    Also, in reference to phase compensation, there is a good article written about phase compensation, if need be.  This was written using a device that is does not have simultaneous sampling. I am adding this just for additional information. Phase-Compensated 8-Ch Multiplexed Data Acquisition System for Power Automation

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Intellectual 440 points

    I did preliminary experiment with AD7606 and it turns out to be that I get around 11bits without filter. With filter not so great improvement. Would like to know if similar test data is available for ADS8568 (for AC and DC inputs). Phase compensation is a complicated process as per your reference article and I do not have sufficient computational time left to execute the algorithm. What would be approximate phase error between channels?

  • 0 in reply to gary mella
    TI__Mastermind 48625 points

    Hi gray,

    I think you have two questions:

    1. Lower bits as expected:  both ADS8584S and ADS8568 should be able to get >13 bits (you were checking ENOB?) if the circuit is designed properly, ADS8584S will be easy to design because it has an integrated ADC driver on each channel. ADS8588S (8ch version of ADS8584S) is completely compatible with AD7606. Let me know your test result with ADS8588S or ADS8584S, we can review your sch and pcb to help you improve it.

    2. Delay/phase error between channels on ADS8584S or ADS8568:  these two devices are simultaneous sampling SAR ADCs, they are different from non-simultaneous sampling ADCs which have a phase difference between channels. Your front-end components can have the biggest contribution to the phase error between channels.

    Thanks.

    Regards,

    Dale

  • 0 in reply to Dale Li
    Intellectual 440 points

    Hello

    I need 14 bits for my application. Let me know the conditions (including power supply requirements, PCB layout guidelines) to achieve the same.

  • 0 in reply to gary mella
    TI__Mastermind 48625 points

    Hi gary,

    ADS8578S is the 14-bit version of ADS8588S, this ADC only needs two power supplies: AVDD=5V and DVDD=3.3V. The pcb guidelines are shown in the section 11.1 of datasheet.

    Regards,

    Dale