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OMAP-L138 + Battery + Touch

1258021
Genius 5120 points
Other Parts Discussed in Thread: OMAP-L138, TPS65070, OMAPL138

Hi,

We are using OMAP-L138 SOM from LogicPD.

In our desing we are using Touch screen which is connected to PMIC.

The observation what we have made is when the system is operating from a 3.7V battery touch pressure value read from ADRESULT_1 and ADRESULT_2 shows a value of 0x3FF always even if we do not touch on screen.

When the system is operating with DC 5.0V volts this issue is not observed.

We are following the same circuitry for Touch Screen as there in EVM.

Please suggest how we can debug?

Regards,
GSR

  • 0
    TI__Intellectual 880 points

    Hello GSR,

                    Is it possible to send the schematics of your Board. Which PMIC you are using ? I am considering TPS65070.

                    1. Please confirm Li-on thermister is properly connected or not?Battery is fully charged / not? What is the Voltage of battery after connecting to the board.

                    2. Pull up resistance of PIMC with OMAPL138?  Voltage of the Pull point when Li-On & 5VDc is connected.

                    3. Battery is charging with PMIC?

                    4 . Please check that what is the voltage change after changing power supply from 5VDC to 3.7V Li-on Battery.

                    5. Check Touch Screen Controller(TSC) is active or standby (TSCMODE = ?) ?

                    6. please check the Touch Screen ADC reference voltage is proper? Voltage at internal voltage regulator for TSC should be 2.30V for TPS65070.

                    7 Should follow the TSC Equations for measuring Touch Screen

                         Please send the circuit asap.

     

    Regards

    Abhijit

     

     

  • 0 in reply to Abhijit Das84416
    TI__Intellectual 880 points

    Hello GSR,

                        Any update ?

    Regards

    Abhijit

  • 0 in reply to Abhijit Das84416
    Genius 5120 points

    Hi Abhijit,

    The HW team suggested us to enable the VREF by setting Bit:4 in Register:07 of the PMIC.

    Any how, we are observing a very low sensitivity with touch panel.

    How can we increase sensitivity?

    Regards,

    GSR