ADS1220: ADS1220 configuration issue

Oliver Ou

Intellectual 2845 points

Part Number: ADS1220

Hi,

Customer uses ADS1220 in diffenttial mode with below experiment:

(1)cut off the input with"X" label, using AIN0 and AIN1 as its differential channel to test

(2) input the power voltage between AIN0 and AIN1, then make some sample test, the data rate is about 0.5s

(3) got the test result in attachment.

sheet1's data is based on the registers' value: 0x60,0x00,0x50 and 0x00

sheet2's data is based on the registers' value: 0x61,0x00,0x50 and 0x00

ads1220测试.xlsx

the question is that why the sample data is wrong, when the PGA is configured, can you make some explanation?

over 7 years ago

0 Bob Benjamin over 7 years ago

TI__Guru** 113765 points

Hi Oliver,

Most likely the input voltage source does not meet the common-mode input requirements when the PGA is enabled. At a gain of 1 with PGA enabled, the inputs must be within the correct common-mode input range as defined by equations 13 through 15 in the ADS1220 datasheet shown on page 22.

An input source that comes from an AC powered instrument can easily float outside the ground reference of the power supply to the ADS1220. With PGA disabled and bypassed, the common-mode restrictions are greatly relaxed.

Best regards,

Bob B

0 Oliver Ou over 7 years ago in reply to Bob Benjamin

TI__Intellectual 2845 points

Hi Bob,
Thanks a lot for your clear explanation and suggestions.

0 Oliver Ou over 7 years ago in reply to Bob Benjamin

TI__Intellectual 2845 points

Hi Bob,
Thanks a lot for your explanation and suggestion.

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ADS1220: ADS1220 configuration issue