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Original question:

TMUX1209: TMUX1209PWR POWER SOURCE

ADS1261: ADS1261BIRHBR ADS1261BIRHBR Inside Mux

Muzaffer Nizam
Prodigy 50 points
Part Number: ADS1261

Tool/software:

Hi,

Could you please tell me about the internal MUX of the ADS1261BIRHBR? I couldn't understand the MUX's block diagram from the datasheet. There is no detailed information about it.

This is important for me because I would like to use the ADS1261BIRHBR in the following configuration and achieve maximum gain. The first step is to achieve a gain of 5 using a fully differential opamp, and the second step is to achieve a gain of 128 using the ADS1261BIRHBR.

Is this possible?

Additionally, I might use a current source with the ADS1261BIRHBR for measuring RTD sensors.

Thank you.

  • 0
    TI__Guru 51676 points

    Hi Muzaffer Nizam,

    The ADS1261 datasheet has a section covering the analog inputs in detail (9.3.1), as well as a subsection covering the analog multiplexer (9.3.1.2). Can you be more specific with your questions? What exactly do you want to know about the multiplexer?

    It is never a good idea to use two gain stages and then have a small gain in the first stage and a large gain in the second stage. This is because the large second stage gain amplifies the noise of the first stage, so you are probably making your noise performance worse by designing your system in this way. See this video for more information about this topic: https://www.ti.com/video/series/precision-labs/ti-precision-labs-analog-to-digital-converters-adcs.html?videoId=6222578382001. That video also discusses why having a gain of 5*128 = 640 is not necessarily beneficial to your system

    Why not just use the ADS1261 as-is? The ADS1261 has a 5x differential inputs (the TMUX only has 4x) and has current sources for RTD biasing integrated into the device (see section 9.3.6 for more information). The ADS1261 also has a very low noise amplifier that is equal or better compared to almost any discrete op amp

    -Bryan