ADC5140EVM-PDK: It is best to measure the noise floor with the differential inputs shorted together and AC coupled to GND.

user6547614

Intellectual 340 points

Part Number: ADC5140EVM-PDK

hi sir

when i test analog differ signal 1channel with IIS 16bit,

DRE enable: the SNR=110db

DRE disable:SNR=108db

so,when DRE enable and disable,there is no high effect ???

How can I configure it to have a noticeable effect

over 3 years ago

0 user6547614 over 3 years ago

Intellectual 340 points

and when i config with 32bit IIS normal,

DRE enable and disable,there have about 6db floatting

0 user6547614 over 3 years ago in reply to user6547614

Intellectual 340 points

How does the use of DRE relate to the bit width??

0 Zak Kaye over 3 years ago in reply to user6547614

TI__Mastermind 23050 points

Hi,

I'm a bit confused by your measurements. The theoretical maximum SNR that can be achieved with 16-bit resolution is 98dB, and there will always be some noise energy so you should measure somewhat less than this in 16-bit mode.

The DRE works by taking advantage of the fact that the SNR of the front end PGA is better than the SNR of the ADC, so that the system performance is limited by the PGA noise rather than the ADC noise. Since the performance of the ADC though is inherently better than 98dB, using the DRE in 16-bit mode does nothing because the SNR is limited by your bit depth, not by the PGA or ADC noise. If you want high performance, you should use 24-bit or 32-bit formats. I hope this helps!

Best,

Zak

0 user6547614 over 3 years ago

Intellectual 340 points

About the relationship between the output quantization SNR and the encoding bit N in the PCM system, the statement is correct.

A. The output quantization SNR increases linearly with the increase of N.

B. The output quantization SNR has an upper limit with the increase of N.

C. Under the condition of small SNR, the SNR of output quantization is independent of N.

D. When a single single-frequency sinusoidal signal is input, increasing N can improve the quantization signal-to-noise ratio.

0 user6547614 over 3 years ago in reply to user6547614

Intellectual 340 points

SNR equals to（bit *6+2）dB??

0 Zak Kaye over 3 years ago in reply to user6547614

TI__Mastermind 23050 points

Yes this equation describes the theoretical SNR of an ideal converter. To be a bit more precise, it is typically given as SNR (dB) = 6.02*N + 1.76

Best,

Zak

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ADC5140EVM-PDK: It is best to measure the noise floor with the differential inputs shorted together and AC coupled to GND.