Analog Discovery USB isolation




Intro

Back when I was deverloping the PSU burner, I wanted to have the Analog Discovery isolated from the common ground, to avoid noise and other issues. Since I did not have a way to do this, I ended up using a laptop on battery for measurements. But for long term, I needed to have this isolation. Unfortunately, things that can isolate USB at 480Mbps or faster are too expensive to justify.

The solution

The ADUM3160 isolator can provide a magnetically isolated 12 Mbps connection, which proved to be good enough. I grabbed one ready made isolator module from ebay for about $12, cheap enough. Well, it is not perfect: the B0505S DC/DC converter provided can only supply 1W and the Analog Discovery is a hungry beast.

 Analog Discovery

Luckily, these DC/DC converters are cheap and I had some more in my parts bin.  Their internal structure allows them to be connected in parallel, so I used 3, which should cover the 2.5W needed.

Next up, I had to upgrade the input fuse, to allow for higher current, my parts bin provided 0.65A one. Given the efficiency of the converters, this his slightly too small, so I would advice for a 0.9A one, the limit of USB 3 ports. Next up I have used an extra wire to connect the output of the DC/DC converter because the PCB trace was too small, dropping 0.3V on it already. Added an extra 470uF capacitor for decoupling, just to be sure.

for more detail: Analog Discovery USB isolation




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