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LM4040: Calculate the worst Vz variation with temperature for LM4040C30I?

Howard Zou
Genius 12365 points
Part Number: LM4040


Hi,

my customer is using LM4040C30I as ADC reference.

And they find that their ADC digitized code would variate with the same analog input when temp changes.

So they would like to figure out what's the worst Vz variation when temp changes from like 0C to 50C.

In

6.12 LM4040C30I, LM4040D30I Electrical Characteristics

We only have Average temperature coefficient of reverse breakdown voltage maximum value at Iz=1mA for full temp range, but we are not working at this current rating, for example, Iz is 5mA in the circuit.

So how I can calculate the maximum variation of Vz with the temp change?

  • 0
    TI__Intellectual 1735 points

    Hi Howard,

    I am looking into this - I will get back to you within 24 hours.

    -Tony

  • 0
    TI__Intellectual 1735 points

    Hi Howard,

    Thanks for your patience. 

    In table 6.5, look at the parameter for "Reverse Breakdown Voltage Change with Operating Current Change" like below:

    If you IR > 1mA, then use the bottom value (8mV) for full temperature range, or if IR < 1mA, use the top value (1mV). Add that value to the one from 6.12 that you already have (which is 150ppm/C for your case).

    For 2.5V at 5mA, this ends up being (150ppm/C)*(2.5V) + 8mV = 187.5uV/C + 8mV for what your worst case tempco is under a different IR than 1mA. let me know if this helps you out.

    -Tony