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ADS1148EVM-PDK

Dvin Amirian
Prodigy 10 points
Other Parts Discussed in Thread: ADS1148EVM-PDK, ADS1148, ADCPRO

Hello,

 

I have a few questions regarding the ADS1148EVM-PDK. The ADS1148 has 4 Channel Differential Inputs. I am planning to use these inputs to connect 3 two wire RTDs. Does the ADS1148EVM-PDK allow access to those channels in order to connect RTDs? The ADS1148 has an internal temperature sensor. Does the software that is provided allow to read this sensor information? Is there any source code available for the ADS1148EVM-PDK or ADS1148EVM? Also, I am planning to use 3 1000 Ohm RTDs and want to know how the chip functions. Do all channels receive current continuously and the multiplexer only switches to read values from different channels? Do the chip provide current to the RTD after multiplexing? For 1000 Ohm RTDs, does IEXC1/IEXC2 need to be used to provide more current?

 

 

Thank You for your help!

 

Dvin

  • 0
    TI__Guru* 98195 points
    Dvin,


    The ADS1148 has an 8-input mulitplexer on the front end. Really you can select any input as the ADC positive input and any other input as the ADC negative input. Often we say that it has 4 differential inputs, but really we're just grouping them in pairs.

    ADCPro software can be used to read the internal temperature sensor. However, the output data is only reported in Voltage or output data codes. You'll need to convert these values to get a temperature.

    I don't know if there's any source code for the ADS1148EVM that I can provide. I've pointed out something for the ADS1248EVM which is very similar (24-bit ADC instead of a 16-bit ADC). Regardless, look at this link:

    e2e.ti.com/.../48321

    Again, the input of the ADC is a multiplexer and with only two IDAC current sources and two ADC inputs (positive and negative). Each one of these is switched independently so a channel that is not selected does not have anything on it and there are no currents going to it.

    Currents from the IDAC go to the pins before the mux, so that the IDAC current never sees the mux resistance.

    IDAC currents go to 1.5mA each, so with a 1000Ohm RTD, you can get 1.5V. This is enough to get a reasonable reference and measurement signal.


    Joseph Wu