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ADS 1148 Programming and communication &temperature sensors

Georgios Kefis
Intellectual 450 points
Other Parts Discussed in Thread: ADS1148, ADS1248

Hello to everyone. I am trying to make an application in which there is the ability to use temperature sensors and for this reason i 've decided to use the ADS 1148 ic. My question is the following: since the device converts the data from analogue to digital the device has to be programmed somehow in order to be able to convert-callibrate the received data correctly (ΔΣ function and so on) but i do not see how using a specific hardware module for the communication between the ic and the a controller. I have to use some pins of it which are ? 
the communication with my controller is done with the usage of the SPI Interface. Could someone please enlighten me ?Thanks in advance!!

  • 0
    TI__Guru* 92715 points
    Georgios,


    As you mention, the ADS1148 uses SPI communication to convert, calibrate and set up the device. Like most SPI, this is done through control of SCLK, DIN, /DRDY, DOUT, /CS. This device uses the START pin to start a conversion and the /RESET as an dedicated reset as well.

    We don't sell specific solutions to communicate with parts. Usually this is done with some sort of microcontroller which the user will have to connect and program to make functional systems. We do make a variety of devices like the MSP430 series that can be used for this purpose.

    As an example, look through this post and it's attachment:

    e2e.ti.com/.../292787


    Joseph Wu
  • 0 in reply to Joseph Wu
    Intellectual 450 points

    Hello Joseph and thanks a lot for your help. I have another question regarding the layout of this ic. I will use 2 analog inputs of this device including both filters (see here for more info :  Ratiometric measurements). Any guidance how should i place the filters or something that i have to do carefully regarding the layout ?

  • 0 in reply to Georgios Kefis
    TI__Guru* 92715 points
    Georgios,


    I'm not sure if some of the text of your post was missing, but I'll post what I think you were asking about.

    For the input filtering, you should consider what currents you have from the analog inputs and their impact on the measurement. First if you route the excitation current through the resistive part of the filter, this is a large additional voltage error that you will see in the measurement. Also, there are some smaller input currents (like input bias currents in the nA range) that may also add smaller error to measurement, especially if the filter resistors are large (>10k).

    For filters, I often refer back to the ADS1148EVM and the input filtering on the board. It is not a large filter, and does not necessarily try to completely remove all frequencies from anti aliasing. However, I generally have good performance with the EVM. You can also look to the EVM for guidance for the layout.

    Additionally, here are two application notes on the use of the ADS1248 (similar to the ADS1148) with a few examples for measuring RTDs with a ratiometric measurement. There are circuits and equations that can guide you through a design. Links to the application note are posted below.

    www.ti.com/.../sbaa180.pdf
    www.ti.com/.../sbaa201.pdf

    If you still have problems on it, post back with some additional questions.


    Joseph Wu