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LM2903: The schematic and power sequence

Lacey Lin
Intellectual 2900 points

Part Number: LM2903

Hi team,

My customer use the LM2903 as below:

Can you help to answer below questions:

1. Please help to review the schematic.

2. Customer use the same power for the LM2903 and the reference voltage, will this cause the output of the LM2903 is not stable during the power up process?

3. For the output of LM2903, because it's the OD type, is it a must we connect it to the power of LM2903, or we can connect to other power rail?

 

Please help on this.

Lacey

Thanks a lot!

 

  • 0
    TI__Guru 68126 points
    Hello Lacey,

    #1. Looks okay. Input range is not violated.

    #2 - It is "ratiometric" when they use the same reference voltage (supply) - so the common mode voltage will track the supply. The comparator will start to react to the inputs at a supply voltage around 1.6V.

    The hysteresis analysis is complicated by the two 1k resistors on the output that reduce the output "high" swing. I assume the transistor is for level-shifting.

    #3 - Yes. You can pull the output up to any voltage up to 36V, independent of the supply. So if they wish to pull-up to 24V, or 5V, or 3.3V, that is fine - just watch the pull-up resistor current (recommend 100uA to 1mA range).