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ADS1219: Advice on possible pitfalls on using Microcontroller 10bit SAR ADC channels along with ADS1219 channels

Rahul S
Prodigy 20 points
Part Number: ADS1219

I am planning on building a DAQ system using ADS1219 and a microcontroller (ATmega328p) to log values into a PC via a USB interface.

I was planning on using Microcontrollers ADC channels (10 bit)  along with ADS1219's channels to log sensor data (from different sensors) at the same time .

Is it recommended to do so ?

Will there be any effect on the ADS1219 accuracy ?

What are the ways to reduce interference between microcontroller ADC input and ADS1219 inputs.

I plan to use a two layer board. 

  

  • 0
    TI__Mastermind 23275 points

    Hi Rahul,

    welcome to our forum and thanks a lot for your interest in our data converters. Please apologize for the delay in responding as most of our support team is on vacation this week.

    Do I understand correctly that you want to measure the same sensor signal both with the ADC inside the MCU and with one channel of the ADS1219?
    I assume the ADC inside the MCU is a SAR ADC. So the only potential issue I could think of is that the SAR ADC inputs 'load' the sensor signal during the acquisition phase. This will depend somewhat on the source impedance of the sensor, the RC filter that you are using in front of the SAR ADC input and the data rate of the ADC.
    Should there be any loading effect of the SAR ADC on the sensor signal, then the ADS1219 might not measure the sensor signal correctly during this time and you might see a gain or offset error.
    You should definitely consider individual RC filters for the MCU ADC inputs and the ADS1219 connecting to the sensor.

    If the ADC inside the MCU and the ADS1219 measure different sensor signals then I don't see any concerns at all. This is a very common use-case by our customers.

    Most important will be the layout to make sure no digital signals cross the analog signals.
    We usually recommend a 4-layer PCB with our 24-bit ADCs, but you can also make it work with a 2-layer PCB with careful layout.

    Regards,

  • 0 in reply to Joachim Wuerker
    Prodigy 20 points

    Hello Mr. Joachim,

    Thanks for replying to my query,

    ADS1219 is used for measuring signals from Sensor1 (lets say a load cell) while MCU ADC lines are used for measuring different sensors (Sensor2 -LDR etc).

    Should i connect the top and bottom Ground planes (AGND for the ADS1219)  near ADS1219 with a lot of vias so they are all at the same potential?

    We are building a small USB powered  Data Acquisition board.

    Regards

    Rahul.S  

  • 0 in reply to Rahul S
    TI__Mastermind 23275 points

    Hi Rahul,

    as both ADCs are measuring completely different sensor signals I don't see a concern at all.

    Connecting the top and bottom GND planes near the ADS1219 with multiple vias is definitely a good idea.
    Also in general make sure you do not create any unintentional GND loops and that no digital lines are crossing critical analog signals on the top or bottom plane.

    Regards,