<story><title>Macbook Pro frying USB peripherals</title><url>https://discussions.apple.com/thread/8223635</url></story><parent_chain><item><author>Kelbit</author><text>As an electrical engineer - I think incidents like these are a pretty solid argument for incorporating overvoltage protection  into 5V USB peripherals.&lt;p&gt;Even something as simple as a zener clamp with a polyfuse to make a dead-simple crowbar circuit will save a device and won&amp;#x27;t contribute a whole lot to BOM cost.</text></item></parent_chain><comment><author>joshvm</author><text>It&amp;#x27;s a bit odd, most older Macbooks have current limiting ICs on the USB ports. I&amp;#x27;ve found this out when tinkering with devboards and accidentally shorting things. In fact most motherboards have some kind of protection for overcurrent conditions.&lt;p&gt;But USB-C isn&amp;#x27;t limited to 5V, power delivery is at 20V. That might explain what&amp;#x27;s going on here (since the user reports 20V on the output) - it thinks that the peripheral is a power hungry device and it&amp;#x27;s trying to charge it. That&amp;#x27;s a problem, but it could be that the peripheral is poorly designed and is mistakenly asking for power that it can&amp;#x27;t actually handle.&lt;p&gt;Edit: in this case the peripheral seems to be the Macbook charger... and plugging it in causes 20V on all the other outputs with only a dongle plugged in. Oops. Yeah not good.&lt;p&gt;I wonder what happens if you actually load the port? Perhaps it&amp;#x27;ll drop down to 5V? Or maybe it&amp;#x27;ll fry things.&lt;p&gt;That said, my comment above still applies: USB-C relies on &lt;i&gt;both&lt;/i&gt; devices to be compliant with the spec. Otherwise you can get into situations where one device fries the other, or tries to charge things it shouldn&amp;#x27;t, etc.</text></comment>
<story><title>Macbook Pro frying USB peripherals</title><url>https://discussions.apple.com/thread/8223635</url></story><parent_chain><item><author>Kelbit</author><text>As an electrical engineer - I think incidents like these are a pretty solid argument for incorporating overvoltage protection  into 5V USB peripherals.&lt;p&gt;Even something as simple as a zener clamp with a polyfuse to make a dead-simple crowbar circuit will save a device and won&amp;#x27;t contribute a whole lot to BOM cost.</text></item></parent_chain><comment><author>koala_man</author><text>If you were a business major, you would instead put that circuitry in a USB surge protector and sell them for $4.99</text></comment>