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Original question:

ADS131E04: Diffirenences between E , A and M

ADS131E04: Advantage of "Digital gain"

Marvin Gasis Arcangel
Genius 9465 points
Part Number: ADS131E04
Other Parts Discussed in Thread: ADS131A04, ADS131M04,

Hi Team,

Can you help with the inquiry below?

I understand that this ADS131A04 device has no PGA integrated and the gain that is featured is implemented "digitally" which means noise performance does not improve when the gain is scaled. In this case, would you kindly explain what is the purpose of the "digital" gain? Since after the delta-sigma ADC you will have some small voltage say nV, then you go into the CS interface and output SPI signals. So whatever this "digital gain" is, just amplifies the signal+noise but only after the analogue is converted to digital so it will just use up more of the bit resolution? Whereas the chip with the PGA will amplify the signal+noise analogue then convert to digital then you are using whatever bits you can depending on the size of the digital signal after gain. And presume in principle the PGA will help improve this SNR since it's done before the analogue to digital conversion.

Is my understanding correct? If not could you clarify why this "digital gain" is not as ideal as the PGA for a very small input signal (nV to pV).

What is the advantage of a digitally implemented gain (ADS131A04) Vs PGA (ADS131M04, ADS131E04)? 

Thanks!

Regards,

Marvin

  • 0
    TI__Mastermind 37330 points

    Hi Marvin,

    The digital gain does not improve device's performance and it just does signal processing on the digital side. It is usually used on delta-sigma ADCs where they require higher gain (>32) because of  less noise improvement, power consumption and so on with PGA implementation. The higher gains on M04 are actually digital gains as well. For A04, this is the result of comprehensive consideration in terms of cost and application.

    Regards,

    Dale