Gain setting in ADS1248

Yagnik Patel

Other Parts Discussed in Thread: ADS1248

Hi all,

I am using ads1248 for my project with bipolar supplies i.e. -2.5v and +2.5v. Everything is working fine but have observed that gain in single ended input is not exact multiple of the reading.for example for any voltage the reading is 200000H then PGA of 2 is giving reading of 300000H rather than 400000H. With differential inputs the gain is as expected(direct multiple). Can anyone please clarify that ? or whether i a making any mistake ?

Regards

Yagnik

over 14 years ago

0 Luis Chioye over 14 years ago

TI__Guru 55466 points

Hi Yagnik,

Welcome to the forum! The ADS1248 device always provides conversions as a function of the differential voltage across the AINP and AINN inputs... Provided that both inputs are inside the allowed common-mode voltage range; the device will provide linear results. Both AINP and AINN must be more than 0.1V from the AVDD/AVSS analog supplies (more than 0.1V depending on the PGA gain and differential voltage across the inputs). The link below provides a more detailed explanation of the common-mode voltage requirements of the ADS1248.

http://e2e.ti.com/support/data_converters/precision_data_converters/w/design_notes/input-voltage-range-requirements-for-the-ads1248-and-ads1148-families.aspx

What exactly is meant by single-ended, is this with the AINN connected to GND? Can you please provide a schematic that shows how the AINP and AINN inputs are connected on both cases the single-ended and differential-ended?

Thank you and Best Regards,

Luis

0 Yagnik Patel over 14 years ago in reply to Luis Chioye

Prodigy 20 points

Hi Luis,

Thanks for quick reply. It was really helpful and almost solved my problem.

Thanks again.

Regards,

Yagnik

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Gain setting in ADS1248