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The datasheet of MCP73831 (a small LiIon charger device) recommends a transzorb on the USB power input (VDD) for input over voltage protection. See Section 6.1.1.2.

Absolute maximum ratings for VDD is listed as 7.0V plus 4kV human body ESD and 400V machine model ESD.

Most transzorb/TVS/varistor devices that allows 5.1V, can be at 7V before the shunt current reaches 1mA and will specify a clamping voltage of 15-35V for higher currents.

Looking at some hobby devices using the same chip does not help. All these Sparkfun product designers clearly ignored the datasheet recommendation.

So what transzorb device did the datasheet author have in mind?

ADDED Apr 1, 16:

As an example of how the voltage waveform may look without any transzorb device during the USB plug-in event is shown below.

Vdd peaking just above 7V when plugging in a 5m USB cable

This is using a 5m USB cable to a standard USB wall adapter.

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  • \$\begingroup\$ Looks like this is a registered trademark for a snubber transient diode. You should be able to just choose an appropriate diode. Given the application, probably a Schottky (but this is a guess, not an answer.) \$\endgroup\$
    – user65586
    Mar 30, 2016 at 15:03
  • \$\begingroup\$ @jdv A diode may suppress a too negative voltage. Not bad, but that's not what we are after here. The plug-in event will create a too high voltage. \$\endgroup\$
    – Rolf Ostergaard
    Mar 31, 2016 at 5:29
  • \$\begingroup\$ Even Vishay, the holders of this trademark, call it one of these: en.m.wikipedia.org/wiki/Transient-voltage-suppression_diode basically, two fast diodes back to back. \$\endgroup\$
    – user65586
    Mar 31, 2016 at 12:24
  • \$\begingroup\$ Ahh I see what you mean. And the question is what type of TVS can actually save this charger chip? Can you actually find a TVS that would work? \$\endgroup\$
    – Rolf Ostergaard
    Mar 31, 2016 at 17:11
  • \$\begingroup\$ Yeah, that's the part I'm not so great at. I'm not sure what the key items in the TVS datasheet you'd need to meet or exceed for your charger. But, I'm smart at searching SE, and I found this: electronics.stackexchange.com/questions/22489/… Maybe this will help? \$\endgroup\$
    – user65586
    Mar 31, 2016 at 17:25

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