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LM2903: LM2903PWR

Jordi Torrents
Prodigy 10 points
Part Number: LM2903
Other Parts Discussed in Thread: LM393LV

Tool/software:

Hello,

I mount LM2903PWR on a PCB board, but I find that in some PCB the component is working well, but in other PCBs is isn't working properly. I verified that all PN an they ara ell the same, but I saw that there ara two different marking code. The chips with the marking: 

Logo TI 38

L2903

2o

work correctly, but the components with marking:

Logo 32

L2903

don't work.

Do you know any kind of difference bettwen thes two chips that could make my desing not work correctly?

Attached you will find both components OK and NOK and the part of the schematic affecteb by LM2903PWR.

Thanks.

  • +1
    Guru 316690 points

    This circuit uses a reference voltage (R556/R557) of about 4.1 V. But with a 5 V supply, the input common-mode voltage range of the LM2903 goes only up to 3 V. When both inputs are above 3 V, the output is random, and this is different for these chips.

    You could change R556/R557 to set a threshold not above 3 V, and adjust R555/C221 so that the timing is correct again. Alternatively, use comparators with rail-to-rail inputs like the LM393LV‍PWR.

  • 0
    TI__Guru 60236 points

    Hello Jordi,

    There was a PCN to change the die in 2022.

    As Clemens points out, you are violating the input range (>3V) and the output behavior during this time depends on which version of the die you received.

    Please see the following Appnote:

     Application Design Guidelines for LM339, LM393, TL331 Family Comparators

    The quick-fix is to use a LM393LV, which has a rail-to-rail input and will not have the input voltage limitation.

    You probably have both versions. One happens to give you your "preferred" output when out of range.

    Since this is a high volume device from multiple assembly locations, we would need the lot codes from either on the back of the device, or, from the reel/box labels.

    But most likely you have a Ji1 (original) device and a Ji3 (PCN#1) device. Without the lot code, I cannot tell which you have as both die were available at the time.