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DLPA2005: RGB operation is different if I press the IC by hand

Chase Jeong
Genius 4670 points
Part Number: DLPA2005
Other Parts Discussed in Thread: DLPC3470

Hello TI experts,

My customer designed DLPA2005 and DLPC3470 for their product, recently they found a problem in their solution.

the problem is, RGB operation is different between the IC is pressed by hand, and just normal operation.

here are the waveforms and color of DLP product.

1. normal operation

2. when press IC or bend the PCB

You can see that RGB anode level is low when B LED ON compared to normal operation, finally the LED looks like blue color is very weak. (it looks like light green)

the question is,

1. was there any issues like this before?

2. what is the reason of this issue?

3. should we modify schematic or artwork, or mechanical structure to avoid this issue?

please let me know if you need more information about this issue. Thanks.

Best regards,

Chase

  • 0
    TI__Genius 16900 points

    Hi Chase,

    This is strange operation. Did you base your system design on a TI reference design?

    Since this issue is sensitive to pressure on the IC I suspect it may be related to a poor solder connection. Is this issue seen on multiple boards?

    Regards,

    Arthur Brown

  • 0 in reply to Arthur Brown
    Genius 4670 points

    Hi Arthur,

    Thank you for your reply.

    here is more information from the customer ;

    1. they followed TI reference design for their schematic.

    2. they re-worked with new IC and heat gun, but it appeared again.

    3. it is seen on every boards, even it have differences how strong should I press each boards.

    and here is one more thing they tested.

    - if they set the current value of LED low, this symptom can re-produce easily. but they set the current high, they hardly re-produce it.

    - they designed some vias on exposed pad for DLPA2005. they think that the impedance through via would be changed when they press the IC or bend the PCB. so the current would be changed and this symptom happens.

    => is it possible situation?

    please check this issue. Thanks,

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Expert 3360 points

    Hi Chase,

    We are still looking into this and will reply shortly.

    Thank you,

    Chris