Adding ESD Protection on Miuni32

ATmega32u4 reference does not delve into the details of ESD protection in the USB circuitry. It merely mentions this:

Although TVS chip is simple to apply, I can’t be too careful since there is more than one type. And since ESD is something I can’t readily test on my own, I must make sure the choices are effective. Searching on StackOverflow led me to a few useful posts. This one discusses how 2 TVS diodes have the exact same SOT-23 IC packaging, but functionally very different (one is unidirectional while the other is bi-directional). To be honest I am still not clear on when to use which. I think the gist is that bidirectional TVS chips are used for data lines (such as USB D+ and D-), and unidirectional ones are used for DC circuit.

My 1st choice is TPD1E10B06 from TI:

As you can see, it is a dead simple part. It is standard 0402 package, bi-directional and can easily be reworked if needed to. The only downside is that I need 2 of these… and that it actually doesn’t support USB 2.0.

My 2nd choice is the following, found in this ESD guide from TI:

The ESD122 is a small bi-directional 2 channel ESD protection diode. The price is right and it is very simple to use. The packaging is 3X2SON, which is difficult to work with hands, but luckily I don’t plan to do that.

3rd choice is the most expensive, but the most simple solution CGA-MLC from Bourns:

This comes in 0402 / 0603 package. Dead simple, but pricey especially when I need a pair of these on every Miuni32.

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