ADS1258-EP: Internal System Readings in Autoscan with Chop Enabled

Ashik A

Part Number: ADS1258-EP
Other Parts Discussed in Thread: ADS1258

Hi,

I am using the ADS1258-EP in Auto-scan mode (using Start pin for conversion). I set the CONFIG0/CONFIG1/MUXSCH/MUXDIF/MUXSG0/MUXSG1/SYSRED during initialization of the system in which I am using the CHOP function (CHOP=1). I would like to get the Internal System Reading particularly the GAIN reading. In the datasheet, it indicates that you need to set CHOP=0 prior to taking the GAIN reading. I was wondering if the ADS1258 automatically sets CHOP=0 prior to taking the reading in Autoscan?

Thanks

over 2 years ago

+1 Bryan Lizon86 over 2 years ago

TI__Guru 51846 points

Hi Ashik A,

The ADS1258 does not automatically set CHOP = 0. If you want to measure the GAIN channel, you must turn off CHOP by writing to the appropriate register

-Bryan

0 Ashik A over 2 years ago in reply to Bryan Lizon86

Prodigy 20 points

Bryan, thanks for the quick reply!

0 Bryan Lizon86 over 2 years ago in reply to Ashik A

TI__Guru 51846 points

Hi Ashik A,

No problem, I am glad your issue was resolved quickly

-Bryan

0 Ashik A over 2 years ago in reply to Bryan Lizon86

Prodigy 20 points

HI Bryan,

Quick follow up question: I was asking this because I was looking to do both a Gain and Offset Correction. The way I was going to do this was by setting CHOP ON and then using the Gain Reading from the ADC. Note: I am also using an external gain stage.

Since I can't do this now, can you provide a good way to do Gain and Offset Correction? I am thinking the only way is to set the CHOP OFF then use the Gain and Offset readings from the adc. But the issue I see with this is that the Offset reading includes the offset of the external stage multiplied by the gain of the ADC added to the ADC offset.

0 Bryan Lizon86 over 2 years ago in reply to Ashik A

TI__Guru 51846 points

Hi Ashik A,

You can always manually perform an offset / gain calibration using external signals. This might be the best approach considering that the GAIN reading on the ADS1258 does not measure the gain error of the external conditioning circuitry, only the ADC itself (refer to Figure 35). Therefore, in your application, it might not be that useful anyway.

-Bryan

0 Ashik A over 2 years ago in reply to Bryan Lizon86

Prodigy 20 points

Hi Bryan,

Thanks again!

0 Bryan Lizon86 over 2 years ago in reply to Ashik A

TI__Guru 51846 points

You are welcome Ashik A!

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ADS1258-EP: Internal System Readings in Autoscan with Chop Enabled