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LM136A-2.5QML-SP: How does the Adjust pin work?

William DeCook
Prodigy 50 points

Part Number: LM136A-2.5QML-SP

How does the Adjust pin of the LM136A-2.5QML-SP work? From the Electrical Characteristics DC Parameters table in the datasheet, it looks like a higher Vadj voltage will result in a higher Zener Voltage, but that's pretty vague. There's no equation or design example to show a specific application. 

I want to minimize the temperature coefficient, similar to what is shown in Figure 3, but I'd rather not put a potentiometer into my design. Is there any method to choose two precise resistor values that will set Vz to 2.49V without having to adjust a pot?

  • 0
    TI__Expert 8390 points

    Hi William, 

    The ADJ pin gives the user the ability to manually trim the nominal zener voltage. As you mentioned, a higher Vadj voltage typically increases the zener voltage and likewise for lowering - this was likely never specified further because the ADJ pin is mainly intended to provide a custom trim for any given part. 

    A potentiometer could be used for initial evaluation to find appropriate approximate resistance values for a given device, then replaced with two precise resistors for a final design. 

    Thanks,

    Sarah