open-ephys / acquisition-board

Hardware interface for streaming up to 512 channels of neural data via USB
https://open-ephys.github.io/acq-board-docs/
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Zener diode (and orientation) missing on silkscreen #9

Closed cxrodgers closed 9 years ago

cxrodgers commented 9 years ago

The Zener diode exists in the solder mask / solder paste layers, but is not marked on the silkscreen. I figured out where it's supposed to go based on the board_centroids file, but I'm not sure about its orientation.

At first I thought Zener diodes were bidirectional, but the datasheet is pretty specific that Pin 1 goes over the power line and Pin 2 goes to ground. See Figure 11: http://www.ti.com/lit/ds/symlink/tpd1e10b06.pdf

Can someone tell me which orientation that should be on the board? See image here: zener The Zener diode is in the lower right corner. It looks to me like the ground pin (Pin 2) should be on the left, connected to C1, and the power pin (Pin 1) should be on the right, connected to Polyfuse. But please verify for me. Thanks!

aacuevas commented 9 years ago

The ESD zener is almost symmetrical, so even if you put ir backwards it wouldn't be much of a difference. That said, the proper way to solder it is as you say: Pin1 to the fuse at the right and pin2 at the left, connected to the capacitor and gnd.

The thing is, there is a little line in the board layout that marks pin1, but it isn't present in the gerber files. We'll have to update them.

jvoigts commented 9 years ago

Hi, good catch! I just put the diode in assuming it was symmetrical, but you're right that they specify pin 2 over gnd, even though they also say that it's symmetrical. I'd say just to be safe let's stick with their recommendation, and put pin2 on the left over ground as you inferred. I'll see if i can make this clearer on the eagle source files.