ADS131E08: Why is Vpp much larger than 6.6 times Vrms

Ruixin Feng

Intellectual 1965 points

Part Number: ADS131E08

Hi team,

Customer test the EVM and internal short input. The noise result is shown as below. Vpp is much larger than 6.6 times Vrms. Could you pls help me understand the reason? And any suggestion that can improve Vpp of noise?

Thanks!

B&Rs,

Rayna

over 1 year ago

0 Ruixin Feng over 1 year ago

TI__Intellectual 1965 points

0 Cole Macias over 1 year ago in reply to Ruixin Feng

TI__Mastermind 18900 points

Hi Rayna,

This is expected, please see this TI Precision labs video on the topic: https://www.ti.com/video/series/analog-to-digital-converters-adcs.html Go check out the noise section ADC noise measurement, methods and parameters video.

Below is a relevant plot from the video. As you can see 6 standard deviations, or ~6*V_RMS is a standard way to predict noise for a Gaussian distributed noise plot.

I don't know what your settings for gain, reference, and sample rate are, but you can back calculate using the equations in the datasheet and compare against your settings:

I'm not sure if you changed the reference, data-rate, or gain, but solving for V_RMS and comparing with the standard deviation gave me something around 111dB which correlates with 4kSPS

Best,

-Cole

Data converters

Data converters forum

ADS131E08: Why is Vpp much larger than 6.6 times Vrms