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ADS1220: Clarification on Effective Resolution of ADS1220 with Internal Reference and PGA Settings

MANOJ V
Prodigy 30 points
Part Number: ADS1220

Tool/software:

Dear Texas Instruments Support Team,

We are planning to use ADS1220IPWR ADC in our application. We want to use internal reference voltage (2.048V) and internal PGA (1 and 2 factor)

Analog input side, we will be providing a single-ended input signal to the AIN1 (Pin 10) analog input of the ADC and planning to float  AIN0, AIN2, AIN3 (Pin 11, 7 ,6). We have two input scenarios:

  1. Case 1: The input signal varies from 0V to 2V, connected to the AIN1 pin and an internal PGA with gain = 1 is used.
  2. Case 2: The input signal varies from 0V to 1V, connected to the AIN1 pin, and the internal PGA is set to gain =  2 is used

For the above said scenario, can you please clarify the below queries:

  • Single ended connection of the analog input mentioned above is proper?
  • What is the effective number of bits (ENOB) we can expect from the ADC with the above said configuration?
  • +1
    TI__Guru 52316 points

    Hi MANOJ V

    Yes, a single-ended connection will work here, and the ADS1220 is capable of single-ended measurements

    The ADC noise depends on the data rate. The effective resolution will be largest when the input signal is maximized. Use equation 1 from the image below to calculate the effective resolution, but use your input signal (2V) instead of "Full-Scale Range" in the equation. Use the appropriate noise value from the table, which varies as data rate and gain changes.

    This will give you the theoretical maximum effective resolution that your system can achieve

    -Bryan

  • +1 in reply to Bryan Lizon86
    Prodigy 30 points

    Thanks for the details, One follow up question on single ended connection is as bellow can u please confirm,
    We are connecting analog input to AIN1(pin 10) and AIN0(pin 11) to analog ground and as we are not using other analog channels we are keeping them floating AIN2(pin 7) and AIN3(pin 6). Please confirm this is fine.

  • +1 in reply to MANOJ V
    TI__Guru 52316 points

    Hi MANOJ V

    The answer to your question is in section 9.1.5 in the ADS1220 datasheet

    -Bryan