ADS1220: Does the ADS1220 Excitation Current Sources IDACs Current match varies with respect to the Loading?

Komal Charan Garlapati

Prodigy 80 points

Part Number: ADS1220

We are using ADS1220 in one of our RTD applications and the datasheet mentions that the current match is +/-0.3%.

Does this value increase with the loading?

over 2 years ago

+1 Bob Benjamin over 2 years ago

TI__Guru** 112775 points

Hi Komal,

The IDACs are constant current sources, so as long as the compliance voltage is met the current remains constant regardless of loading. The IDAC mismatch may affect a 3-wire RTD measurements resulting in improper lead cancellation when 2 IDACs are used. This is discussed in detail in A Basic Guide to RTD Measurements. Look particularly at section 1.4.1 on Lead Resistance Calculation and section 1.4.2 on IDAC Current Chopping used to cancel IDAC mismatch in the measurement.

IDAC mismatch error is affected by device temperature. Figure 29 in the ADS1220 datasheet shows the typical response for commonly used currents over device operating temperature.

Best regards,

Bob B

0 Komal Charan Garlapati over 2 years ago in reply to Bob Benjamin

Prodigy 80 points

Thank you Bob.

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ADS1220: Does the ADS1220 Excitation Current Sources IDACs Current match varies with respect to the Loading?