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ADS114S06B: Noise Issue in ADS114S06B

bruno macedo
Prodigy 10 points
Part Number: ADS114S06B
Other Parts Discussed in Thread: ADS114S08B

Dear All,

I am using ADS114S06B as can be seen in the SCH in attachment. It was designed to measure thermocouples.

When operating my final product with power contactors, the A/D is subjected to noise and it stops working: when sending readdata command (continous mode), the answer from A/D is 0 (data, status register and CRC).

Can somone help me to solve this issue?

B.R,

INPUT.pdf

  • 0
    TI__Guru** 113765 points

    Hi Bruno,

    Welcome to the E2E forum!  When you mention the use of power contactors,  Are these contactors operating external to the PCB (like turning on a motor)?  Strong EMI/RFI can enter the system by cabling acting as an antenna.  Extra precaution may be required to prevent large transients from entering the measurement system.

    You may need to add TVS diodes to limit the transient.  I see that you have some diodes on the TC input at R7, but this connects to the reference and not to a ground point (preferably earth ground) where the transient should be delivered.  The reference input directly connects to the ADC input at AINCOM.  As the TC would connect to input connectors labeled 2 and 3, lots of transient current could enter at AINCOM.

    The current into the ADS114S08B analog inputs must be limited to no more than a maximum of 10mA.  This would require a series resistance between the reference and the AINCOM pin.  Also, you need to prevent the transient from entering the supply and the shunt reference may not be capable of limiting the voltage quickly enough.  I would suggest adding TVS diodes to the sensor inputs to limit the voltage to a reasonable voltage value.

    Best regards,

    Bob B