ADS1263EVM-PDK: ADS1263EVM-PDK: When using ADS1263 to collect low-frequency or high-frequency signals, using a low-frequency signal along with a high sampling rate will result

danyang feng

Prodigy 80 points

Part Number: ADS1263EVM-PDK
Other Parts Discussed in Thread: ADS1263

ADS1263-test record.docx

2 个月前

0 Vivian Gao 2 个月前

TI__Mastermind 47830 points

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0 Vivian Gao 2 个月前回复 Vivian Gao

TI__Mastermind 47830 points

Can you tell me how the signal is being applied to the EVM? It looks like there could be a common-mode issue

The 1VPP signal should be centered in the ADC supply range. If you are using 5V unipolar supplies, then the signal should be centered at 2.5V

Also, you in general need to ensure you are taking enough samples per period to get a good recreation of the waveform. For example, measuring a 1 Hz sinewave at 5SPS will not be sufficient to adequately reproduce the sinewave

You should also consider the 3dB cutoff frequency of the filter you are using. This will attenuate the response. Refer to Table 9-4 in the ADC datasheet for more information

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

We are using a signal generator which emits a sinusoidal signal with a frequency of 1 Hz or 1 KHz, a peak-to-peak value of 1 V, and without any offset. So the waveform collected by ADS1263 is one that oscillates up and down around 0. What puzzles me is that when a 1KHz sine wave with a peak-to-peak value of 1V is input, why does the amplitude of the collected signal fluctuate so greatly? It is still rather strange as to why, when a 1Hz peak-to-peak 1V sine signal is input, the waveform obtained with an excessively high sampling rate is of poor quality. These two questions

0 Vivian Gao 2 个月前回复 danyang feng

TI__Mastermind 47830 points

The ADS1263EVM does not support bipolar supplies, which means a signal centered at 0V will be outside the ADC common-mode range. Ideally the sinewave should be centered at 2.5V as I stated in my previous post.

You can see this in the image below, also from the EVM. We are using the same settings as you and the sinewave output looks very good

So you have the signal applied incorrectly to the ADC somehow

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

I understand what you mean. The input sine wave cannot be bipolar. Should we use a sine wave with a peak-to-peak voltage of 1V and a bias voltage of 2.5V for the input? Is that correct? Our EVM is powered by a single-ended 5V supply. I would like to ask if the ADS1263 chip can be powered by ±2.5V.

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

+1 Vivian Gao 2 个月前回复 danyang feng

TI__Mastermind 47830 points

danyang feng 说：
Should we use a sine wave with a peak-to-peak voltage of 1V and a bias voltage of 2.5V for the input? Is that correct?

Yes, this is correct and what we did to obtain the sinewave shown in the image I sent you

danyang feng 说：
I would like to ask if the ADS1263 chip can be powered by ±2.5V.

The ADS1263 device supports bipolar supplies (+/-2.5V). The ADS1263EVM does not support this feature however because AVSS and DGND are connected to the same plane / net

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

OK. Thank you.

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

我按照您的方法采集到的波形是下边这个样子的，请问是我这边干扰太大了吗，还是接地工作没做好。

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

I would like to ask, the waveform I captured looks like this. Is it because there is too much interference on my side, or is the grounding not done properly?

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

I would like to ask, the waveform I captured looks like this. Is it because there is too much interference on my side, or is the grounding not done properly?

0 danyang feng 2 个月前回复 danyang feng

Prodigy 80 points

Could you please show me how the hardware of your ADS1263EVM is connected? Just like what I captured above.

0 Vivian Gao 2 个月前回复 danyang feng

TI__Mastermind 47830 points

Yes it looks like you are picking up another signal, maybe 60Hz?

It does also look like you are getting a discontinuity as the sinewave crosses 0, so there might still be grounding issues as well

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

This is a 1Hz sine wave with a peak-to-peak value of 1V. You mentioned that there was a problem with the grounding. You were able to obtain a complete waveform on the upper side at that time. How was the EVM set up and connected?

0 Vivian Gao 2 个月前回复 danyang feng

TI__Mastermind 47830 points

In general, you are making sure that the ADC ground and the signal source ground are shared

Then you need to ensure the sinewave has a 2.5V DC offset

Of course if you are picking up other signals e.g. 60Hz then you will need to remove those / filter them out somehow

0 danyang feng 2 个月前回复 Vivian Gao

Prodigy 80 points

Could you please show me the connection method of the ADS1263EVM circuit on your side? I'd like to take a look at the picture.

0 Vivian Gao 2 个月前回复 danyang feng

TI__Mastermind 47830 points

Below are the images of my setup:

The red wire is the sinewave output from a signal generator (settings are shown in the second image)
The black wire is the signal generator reference e.g. ground, which is connected to the EVM ground
The orange wire connects to AIN3 and to REFOUT (2.5V) on the ADC
The gray wire connects to AIN2 and the red wire from the signal generator

The signal generator has an offset of 2.5V, so the sinewave is centered at 2.5V relative to the ADC / EVM ground. The results are shown in the third image below