ADS1299-4: Dynamic range

Saba Eas

Part Number: ADS1299-4
Other Parts Discussed in Thread: ADS1299

Hi,

Can you explain the implications of narrowing down the dynamic range? Is it merely going to zoom in the entire signal with the input referred noise levels or it would just zoom in the entire signal of interest? Will this be a valid experiment to detect signals with smaller amplitudes? Currently we are using the internal reference.

Thanks,

Saba

7 months ago

0 Saba Eas 7 months ago

Intellectual 300 points

Hi,

Could anyone here help me with this question please?

Thanks,

Saba

0 Ryan Andrews 6 months ago in reply to Saba Eas

TI__Guru 62786 points

Hi Saba - please excuse our delay. Do you still need help with this?

Regards,

Ryan

0 Saba Eas 6 months ago in reply to Ryan Andrews

Intellectual 300 points

Hi Ryan,

Yes, I am still looking for help.

Regards,

Saba

0 Ryan Andrews 6 months ago in reply to Saba Eas

TI__Guru 62786 points

Hi Saba,

For higher resolution ADC's like the ADS1299, increasing the gain of the front-end amplifier stage can help to improve the dynamic range of the system when measuring small input signals. An example is shown in the slide below. More information can be found in our TI Precision Labs ADCs training videos:

https://www.ti.com/video/series/precision-labs/ti-precision-labs-analog-to-digital-converters-adcs.html

Regards,

Ryan

0 Saba Eas 6 months ago in reply to Ryan Andrews

Intellectual 300 points

Hi Ryan,

Thank you for the response. It's really helpful.
We have utilised the max gain to measure smaller inputs and wondering using an external reference that's lower than the internal 4.5V reference could help more in detecting smaller biopotential signals more accurately. If so how? Because this approach would help the entire noise floor to take advantage as well.

Regards,

Saba

0 Ryan Andrews 6 months ago in reply to Saba Eas

TI__Guru 62786 points

Hello Saba,

By decreasing the reference voltage, you are also decreasing the LSB size of the ADC (least-significant bit voltage). However, the magnitude of the system noise does not change; therefore, more bits will toggle randomly due to noise, and you will reduce the dynamic range of the system. It is better to keep the 4.5-V reference voltage. The advantage to an external reference is the ability to improve the drift performance of the reference, which reduces the system gain error over temperature.

Regards,

Ryan

0 Saba Eas 6 months ago in reply to Ryan Andrews

Intellectual 300 points

Hi Ryan,

Thanks for the clarification.

Regards,

Saba

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ADS1299-4: Dynamic range