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TS3A24159: Noise/ Ripple

Plantin Anthony
Prodigy 10 points
Part Number: TS3A24159

Hi,

I'm kind of new in this forum, so I'll try to explain my trouble as simple and clear as I can :), if it's not just let me know ! 

So first of all, the aim of our project is to read a thermistor and connect this termistor to an heating controller. We also want control this heating controller with a digital potentiometer.
To do the job we're using two TS3A24159.

When the thermistor is directly connect to the heating controller everything is ok, the signal is a simple DC signal depending of the thermistor.
But when the signal is going through the both TS3A24159, we have a kind of ripple. And so on the average signal is not the same and when the heating controller read the temperature this is not the same.

Can you please help with some thoughts to rectify this issue. Thanks in advance for your help and support.

Anthony
TSA3A24159.zip

  • 0
    TI__Mastermind 45340 points
    Anthony,

    Thank you for sharing the scope shots and schematic.

    In the schematic it looks like you are using the 2:1 switch (U503) to take the signal from the thermistor and choosing it to go to the heating controller or to the ADC. It also looks like (U505) is choosing the signal from the heating controller to go to see the signal from the thermistor or see the signal from the digital potentiometer. Is my understanding correct?

    When you remove the TS3A24159 from the board and connect the thermistor IN+ and IN- signal directly to the heat controller SET_POINT_+ and SET_POINT_- you see the DC 200mV as seen in image IMG_0076. correct?

    When you place TS3A24159 on the board and you probe the COM 1 and COM 2 pin of the TS3A24159 U505 you see the 200mV DC signal with a periodic (50Hz) slow rising edge from 100mV to 200mV. correct?

    Since the "ripple is periodic", are you toggling the IN1/IN2 pins of the TS3A24159 at 50Hz? The thought is you may be seeing a slow rise time due the high capacitance on the bus.

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    TI__Mastermind 45340 points
    Anthony,

    Have you been able to resolve the issue you were seeing? Do you have additional questions?

    Adam
  • 0 in reply to Adam Torma
    TI__Mastermind 45340 points

    Anthony,

    I haven't heard from you so I will close this thread.  If you have additional questions responding to this thread will reopen it or you may post a new thread.

    thank you,

    Adam