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ADS8166: Settings for use with LMP91000 AFE

Part Number: ADS8166
Other Parts Discussed in Thread: LMP91000,

Hello

I am planning to use ADS8166 with 4 LMP91000 chips. I wish to use the Internal 4.096V reference voltage of the ADS8166 for the LMP91000 to read output from gas sensors like SPEC sensors. I have the following questions.

1. What will be the output range on VOUT of LMP91000 with internal zero at 50% and bias 0%?

2. How do I match the output from LMP91000 to FSR of ADS8166 (0V to 4.096V)?

3. Do I need to add any gain buffer on the REFIO to use it with the 4 LMP91000 chips? The track length between the ADS8166 and the LMP91000 will be around 2 inches.

4. Do I need to add any buffer between VOUT of LMP91000 and AINx of ADS8166?

Regards

Vijay

  • Hi Vijay,

    1.  I suggest you submit a separate e2e post specifically for the LMP91000.  The team that supports this device know it best.

    2.  The output range will depend on the supply voltage and the specific type of gas sensor used.  Assuming a 5V supply, then the output could range from 0V to 5V max.  The following Analog Engineer's Circuit shows how to scale different input voltage ranges to an output suitable for the full scale input range of the ADS8166.

    http://www.ti.com/lit/an/sboa261a/sboa261a.pdf

    Or you can use the Analog Engineer's Calculator tool here:

    http://www.ti.com/tool/ANALOG-ENGINEER-CALC

    Below is an example for scaling a 1V to 3.5V input signal to 0.1V to 4V suitable for the ADS8166:

    3.  I suggest you use the REFby2 buffer output, which is intended to drive external loads.  The output voltage is 2.048V nominal when using the internal reference.  If you want to use the REF voltage at the REFIO pin, then you will need to add an external buffer.

    4.  If you use the voltage scaling circuit above, then you may not need any additional amplifiers.  This will depend on your sampling rate.  In order to get best performance, you will want to add a single buffer between the MUXOUT and ADCIN pins.  Please refer to Figure 102 in the datasheet.

    Regards,
    Keith Nicholas
    Precision ADC Applications