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MSPM0L2228: MSPM0L2228 LCD Ghosting / OFF Segment Visibility Issue

Ranganath Kuntumalla
Prodigy 20 points

Part Number: MSPM0L2228

Dear TI Support Team,

We are using the MSPM0L2228 internal LCD controller with a segmented LCD display.

Current configuration:

  • LCD Mode: 4-MUX
  • Bias: 1/3 Bias
  • Supply: Internal AVDD = 3.3V
  • Charge Pump: Disabled
  • Low Power Resistor Ladder: Enabled
  • Frame Frequency: ~80 Hz

Issue observed:
Some OFF segments are faintly visible (ghosting effect) even when they are not enabled. ON segments are displaying correctly, but OFF segments appear lightly activated.

We have already verified:

  • Correct COM/SEG connections
  • Proper 4-COM configuration
  • PCB cleanliness and LCD connection
  • Different frame frequency settings
  • Contrast adjustment attempts

We would like guidance on:

  1. Recommended LCD settings for minimizing ghosting in 4-MUX mode
  2. Whether low power resistor ladder can cause faint OFF segments
  3. Recommended VLCD/contrast configuration when using only AVDD without charge pump
  4. Any known limitations or best practices for reducing OFF-segment RMS voltage

Please let us know if any additional waveform measurements or configuration details are required.

Thank you for your support.

Best Regards,

Ranganath

  • 0
    TI__Mastermind 31225 points

    Hi Ranganath,

    Ranganath Kuntumalla said:
    Some OFF segments are faintly visible (ghosting effect) even when they are not enabled.

    Is this means that the un-enabled segments are seen some ghosting effect (static display)? Or in dynamic switching, the OFF segments are seen the ghosting.

    I suggest to test these affected pins to record its waveform and compared to other unaffected pins, and analyze its RMS.

    Ranganath Kuntumalla said:
    We would like guidance on:

    For these recommendation, I'll check with internal team and feedback later.

    B.R.

    Sal

  • 0
    Prodigy 20 points

    Hi Sal Ye,

    Thank you for your reply.

    Yes, the un-enabled segments are seen as a ghosting effect in both static and dynamic switching conditions. Not only some segments, but all segments in the display are showing the ghosting effect.

    Kindly check this issue and provide a suitable solution or recommendation to resolve it.

    Looking forward to your support.

    Best Regards,

    Ranganath

  • 0 in reply to Sal Ye
    Prodigy 20 points

    Hi Sal Ye,

    Thank you for your reply.

    Yes, the un-enabled segments are seen as a ghosting effect in both static and dynamic switching conditions. Not only some segments, but all segments in the display are showing the ghosting effect.

    Kindly check this issue and provide a suitable solution or recommendation to resolve it.

    Looking forward to your support.

    Best Regards,

  • 0 in reply to Ranganath Kuntumalla
    TI__Mastermind 31225 points

    Hi Ranganath,

    Sorry for the late response. Please see my quick comments below: 

    For the static ghosting effect, can you check waveform and the RMS value of the OFF segments and then compare to your LCD specifications?

    - If you find the OFF RMS is slightly larger than expectation (check the waveform), then the HP (small resistor ladder) mode will help to reduce it (the optimization is limited, as the OFF RMS voltage majority comes from VLCD).

    - To reduce the OFF RMS, the easier way is to enable the charge pump and configure the LCD to slightly smaller than current VDD supply (3.3V).

    For the dynamic ghosting effect, my initial thought is the frame frequency, you can set it to 60Hz to quickly verify scenarios.

    Additionally, if you are setting the LP mode, you can try the HP mode with smaller resistor in the voltage generator will help:

    I recommend using the charger pump mode for this issue.

    I am OOO this week for business travel and will check your feedback next week. 

    B.R.

    Sal

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