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MSP430FG439: there is a possiblity LCD's SEG pin and COM pin might become shorted

Shunsuke Yamamoto
Expert 4946 points
Part Number: MSP430FG439

Hi team,

Is it acceptable in below cases? Because there is a possiblity LCD's SEG pin and COM pin might become shorted in customer's use case.

1. S0 and S1 are shorted.

2. S31 and COM0 are shorted.

3. COM2 and COM3 are shorted.

Best regards,

Shunsuke Yamamoto

  • 0
    TI__Guru 56685 points

    Hello Shunsuke,

    Please see the following application note for more information of how to utilize LCDs with MSP430s. www.ti.com/lit/slaa654 or www.ti.com/lit/slaa516 

    You should have a network of voltage dividers/bias resistors on the COM pins in some manner, depending on setup. (See above app notes). If things are shorted then the LCD will not display things properly.

  • 0 in reply to Jace H
    TI__Expert 4946 points

    Hi Jace-san,

    Thank you for the reply. I understood that LCD will not display things properly when SEG pins and COM pins are shorted. 

    May I ask you an additional question?

    If one of three shorted cases occurs, MSP430FG439 will get broken?

    Best regards,

    Shunsuke Yamamoto

  • +1 in reply to Shunsuke Yamamoto
    TI__Guru 56685 points

    Shunsuke,

    From a voltage perspective, you should be good as the device can't generate anything beyond VCC going into the device. From a current perspective though, there is a risk if one is set high and the other low. You will then have a large current spike which could possibly exceed device maximums for pin or port. At that point, damage is possible, especially of continued in that state over time. Now, if you never set those pins and leave them floating, then you might be safe.  In the end, the recommendation is to not have these pins shorted. 

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