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TSC2046EIPWR touch controller is getting hang on 8KV contact discharge as per IEC standard 61000-4-2

Siva kumar95216
Prodigy 30 points
Other Parts Discussed in Thread: TSC2046, TSC2046E

Hi,

We are using touch controller PN: TSC2046EIPWR in our automotive control panel project.  But when applying high voltage ESD pulses(+/-8KV contact discharge) on the LCD metal back plate (touch panel is attached with this LCD), touch became non operative.

I have not used any ESD suppression diodes on the touch lines(X+,X-,Y+,and Y-) since the datasheet says no external ESD diodes are required. Anybody has come  across same behavior with TSC2046? Please see the touch controller schematic below...

  • 0
    TI__Guru 52115 points

    Hi Siva,

    I will take a look and get back to you soon.

    Andy

  • 0 in reply to Andy Liu (BMS)
    TI__Guru 52115 points
    Hi Siva,

    Did that TSC2046E device become nonfunctional permanently? Could that device recover after reset? If that device becomes bad forever, I think it will be necessary to do an FA for that device.

    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 30 points
    Hi Andy,
    Thanks for the reply. It is a temporary failure, we have to do a restart to make the system back to working condition.
    Also when a thick metal wire is connected between the LCD back plate and the shield ground on the system cable input, this issue got solved.
    Since we dont want to use an external wire strip in the product (and we dont have provision to add it in the plastic casing), we are planning to install TVS diodes on the C37,C51,C153 and C183 and do a re-test.
    Regards,Siva
  • 0 in reply to Siva kumar95216
    Prodigy 30 points
    Hi All,
    The above post was based on the feedback from our customer on the ESD tests, we have done some experiments and below are the inferences/corrections on above reported issue,

    1. ESD failure is happening only on some particular areas of the LCD/Touch panel (left side and top side to be specific, may be due to panel structure)
    2. Once the touch panel is hung, only power restart of the board can bring the panel to working condition
    3. Terminating the back side metal sheet of the touch panel to the shield ground is not solving the issue
    4. Installing external TVS diodes (SESD0402P1BN-0450-090) on the X,Y lines did not solve the issue
    5. Removed all wire connection to LCD (LCD LVDS Data cable and back light cable ), only touch FPC cable (X,X-,Y,Y-) lines are connected to the PCB, 2CM gap maintained between touch panel and PCB; still on exposure to 8KV ESD pulse, the touch panel hung
    6. While the touch panel is hung , X and Y co-ordinates are read as 4096 ( looks like 12 bit ADC of the touch controller is getting saturated)
    7. Removed the touch panel, and applied 4KV contact discharge directly on the touch connector (just to see the behavior of touch controller ), then we were able to get X and Y co-ordinates as 4096. Same as touch panel hang situation.

    Regards,
    Siva
  • 0 in reply to Siva kumar95216
    TI__Guru 52115 points

    Hi Siva,

    Below are my comments:

    a) Try other types of ESD diodes.

    b)  Another thing that the customer can try is to put a series resistor in the analog lines from the driver to form a low-pass filter on the input, but the series resistor has to be as small as possible (I would suggest resistors of less than 10 ohms).  See the screenshot below: