ADS1278 data acquisition chip data distortion problem

hhqi_super

ADS1278 data acquisition chip data distortion problem [Copy link]

 Have you used TI's ADS1278 for AD acquisition? During the test, I found that if the input signal exceeds the reference voltage, the analog-to-digital converted signal is not a distorted sine wave with a clipped peak, but an output similar to a valid signal output but abnormal. Has anyone encountered this problem? Please give me an answer.

supermiao123

Such a waveform may be a matter of code conversion

hhqi_super

supermiao123 posted on 2019-3-2 22:33 Such a waveform may be a problem with code conversion

Code conversion problem? AD input signal exceeds the reference and the conversion has problems? Is the AD broken? If the reference voltage is increased, the waveform will be restored to a non-distorted state. If the AD itself has this problem, how should it be handled? What if several ADs are in this situation at the same time?

扫地小僧

The code system mentioned above seems to be a problem of incorrect conversion between signed and unsigned decimal. I suggest you send a large DC signal from the front end of the acquisition and compare the acquisition to determine whether it is a software or hardware problem.

y909334873

The data sheet should have a description of the output value when it is greater than the reference voltage. The other TI ADs I use all have this.                                                         

hhqi_super

Posted by Sweeping Monk on 2019-3-4 07:56 The coding system mentioned above seems to be a problem of signed and unsigned decimal conversion. I suggest you send a large DC signal at the front end of the acquisition, and compare the acquired results to confirm...

Well, thank you. For this problem, I increased the reference voltage and there is no distortion. The software should be correct.

hhqi_super

y909334873 posted on 2019-3-4 11:56 The data sheet should have a description of the output value when it is greater than the reference voltage. The other TI ADs I use all have this...

I have also read the manual. The attached picture says that if it exceeds the range, it is a fixed value.

清风化夜

Use an oscilloscope to measure the output of the differential op amp. It seems to be a problem of bias voltage.