App note: Linear regulators reverse voltage protection


Various input and output reverse voltage protection method for linear regulators discussed in this app note from ROHM. Link here (PDF)

A linear regulator integrated circuit (IC) is a DC-to-DC buck converter system that reduces a DC supply from higher voltage level to a lower voltage level, thus it requires that the input voltage is always higher than the regulated voltage. Output voltage, however, may become higher than the input voltage under specific situations or circuit configurations, and that reverse voltage and current may cause damage to the IC. A reverse polarity connection or certain inductor components can also cause a polarity reversal between the input and output terminals. This application note provides instructions on reversed voltage polarity protection for ICs.

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  1. DC to DC “Buck Converter”? That is Utter bolox!

    They are not switched mode systems,
    they are self regulating linear voltage dropping systems,
    that dissipate the unwanted energy as heat.
    Nothing SMPS related in any way, so *very* low noise,
    and with *very* good dynamic regulation.

    Correct and robust reverse I/O polarity protection takes
    a lot more than just a diode between input and output!

    Best read the most excellent National Semiconductor
    (and other) application and data books for these things.


  2. Shocking, ROHM must have got some rubbish new staff or intern to work on this. Watch out, onlines sellers in China are doing the same dumbass thing lately. I’ve corrected one vendor on this in the past month. Of course the Chinese vendor’s excuse was that they do not have the relevant tech knowledge, but I don’t think ROHM can give the same excuse.

    1. Of course, for avoidance of ambiguity, I am following up on Dave noticing the “DC-to-DC buck converter”. So which ROHM staff thinks the FET there is a converter?

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