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I am trying to understand why, in the datasheet, the maximum input voltage of the LT3483 changes.

In the features we have: "Wide Input Range: 2.5V to 16V". However, on the last page, we have an example:

example

Here the max. input voltage is 6 V, and output is -5 V.

Moreover, there is a different document:

Demonstration circuit guide

And there are 2 circuit examples:

These have different maximum input voltages; 12 V for -15 V output, and 4.2 V for -8 V output.

How to compute the max. input voltage?

Is there some rule?

Or is it always 16 V, but in the datasheet it's smaller because of a typo (6 V = 16 V), and capacitors protection in the "Demonstration circuit guide"?

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    \$\begingroup\$ Welcome! Depends on your passive component selection. The IC can withstand at least 16 V. Please simulate it in LTspice and sweep the input voltage to wider than specified for one of the examples to find out. \$\endgroup\$
    – winny
    Commented Aug 4, 2022 at 8:57
  • \$\begingroup\$ So, the only problem is with passive elements? If I use passive components that have much higher voltage and current parameters than needed, I can safely use 16 V? \$\endgroup\$
    – 4a4ik
    Commented Aug 4, 2022 at 12:13
  • \$\begingroup\$ It’s not the passives themself but rather the situation they “program” the IC to operate in. Simulate it! It’s free. \$\endgroup\$
    – winny
    Commented Aug 4, 2022 at 13:16
  • \$\begingroup\$ I simulated and didn't find any difference between 5 V and 15 V for -5V output example. Not in output voltage, not in input current, etc. I think, in examples, they copied them from somewhere, where it matters (due to passive components or something else, not DC/DC performance specifically). Because in the datasheet there is no info about operating voltages for different circuit configurations or output voltages. Thank you very much. \$\endgroup\$
    – 4a4ik
    Commented Aug 5, 2022 at 9:36
  • \$\begingroup\$ What about peak current? \$\endgroup\$
    – winny
    Commented Aug 5, 2022 at 9:54

1 Answer 1

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You need to make a distinction between the absolute maximum voltage limit (above which you can expect IC failure) and, the maximum operating voltage for a specific circuit configuration (above which the output voltage or load current cannot be guaranteed). These are two different things.

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  • \$\begingroup\$ Ok, so input voltage in the examples shows range in which output parameters will be guaranteed. How can I compute them myself? Or simulation is the only way? If I have - 10 V with specific topology for example. In the -5 V example, input voltage can be higher than output. In the -15 V, it should be lower. \$\endgroup\$
    – 4a4ik
    Commented Aug 4, 2022 at 12:09
  • \$\begingroup\$ @4a4ik correct. Simulation is always a good way and can either replace hand calculations or used with them. I don't follow the rest of your comment but, please take the 2 minute tour to understand why folk give free help. \$\endgroup\$
    – Andy aka
    Commented Aug 4, 2022 at 12:41

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