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ADS8166: ADS8867 vs ADS8166

Part Number: ADS8166
Other Parts Discussed in Thread: PGA281, , ADS8867, ADS8924B

Hi support forum

Question1:  For the ADS8166 please look the attached design proposal and make a sanity check and let me know if there is any problem to use just one pair of MUX inputs for the PGA281 differential output signal?

Question2: ADS8166 pin20 ADS-INM, pin17 ADS-INP or is it better to connect the Diff. output from the PGA281 directly to these two inputs and avoiding the MUX in the ADC?

Question3: Or if it is a better choice to go for the ADS8867.

Question4: Are there any recommendation in parts selection for the 10y production in order to avoided any EOL situation?

Br Jørgen Lundbeck

Attachment: 810.009.250MS-01  AIM 2200 Measurement System.docx

810.009.250MS-01 AIM 2200 Measurement System.docx

  • Hello Jorgen,

    The ADS8166 can be configured as either single ended input or pseudo-diff input.  For single ended, the negative input is connected to ground.  For pseudo-diff, the negative input is connected to 1/2*Vref.  The PGA281 output is differential, so to use this part, you would only use the positive output in a single ended configuration, with Vcom set to 1/2/Vref.

    The ADS8867 is a true-differential input ADC, and can directly accept the outputs of the PGA281.  For best performance, I would suggest using this ADC.  Another option would be the ADS8924B, which is a 16b, fully-differential input ADC.  The nice feature of this part is the inclusion of a reference buffer, allowing the use of an external low power reference.

    Question1:  You can connect the PGA281 through the mux or directly to the ADC input pins.  As noted above, you would only use one of the PGA281 outputs, and could configure the ADS8166 input as pseudo-diff, connecting the negative input to 1/2*Vref.  You can also use the same 1/2*Vref signal as the Vcom input to the PGA281.

    Question2:  You can connect either through the adc mux or directly to the adc inputs.

    Question3:  ADS8867 (or ADS8924B) will allow fully differential inputs.  This will improve your noise by a factor of 2, giving you about 1 extra bit of effective resolution when considering noise limitations of the ADC.

    Question4:  All of the ADC's referenced are relatively new devices, and should be around for many years.

    In summary, you could use any of the above ADC's, with the differential ADC's providing better noise performance.  However, you may be limited by noise in other parts of the total signal chain, so this may not be an advantage.  Also, if I understand your requirements, you need a total sample rate period of 75uS, or 13.3ksps.  If this is the sample rate of the ADC, then the PGA281 should be able to directly drive the inputs of any of the above ADC's.  If you need to run closer to 100ksps, then a higher speed buffer between the PGA281 and ADC may be needed for full settling.

    Keith Nicholas
    Precision ADC Applications