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TSC2046 noise issues

Gabi
Prodigy 30 points
Other Parts Discussed in Thread: TSC2046, ADS7846

Hi,

I have a system with TSC2046 controller for a 2.8" TFT (DT028ATFT-TS).  The touch screen is a 4 wire one with 300ohms for X and 600 ohms for Y. 

The analog connections are short, about 1/2 inch, and the touch controller is decoupled locally with 2.2u and 0.1u.

I experience noise, about 100-200 digital units, when TFT is on. The touch readings  are fine when TFT is not initialized. The backlight driver is not adding significant noise to the touch screen readings. 

SW: emWin ADS7846 touch driver., with PENIRQ detection, but no BUSY line.

Not sure what to do next, maybe to add input capacitors?  I would still try to fix the issue on the HW level before filtering this noise.

Any suggestions, please?

Thank you,

Gabi

  • 0
    TI__Guru 52115 points

    Hi Gabi,

    I think you are looking for some solution to deal with LCD noise in your system. I would recommend that you add some several decoupling capacitors, from Y+, Y–, X+, and X– to ground.

    If you need more information on how to reduce the noise from LCD. Here is a very good application note for you to digest:  http://www.ti.com/lit/an/sbaa155a/sbaa155a.pdf

    Andy

  • 0 in reply to Andy Liu (BMS)
    Prodigy 30 points

    Hi Andy,

    Thank you for feedback. The 1nF capacitors and digital average filtering was a good compromise between noise and speed; 10nF was too slow.

    Gabi