As promised in my post about USB PD - CC decoding adventures, here is the conclusion of my journey to a usable tool to debug USB-PD messages on the CC interface. It also shows that picking the correct opamp characteristics is not only a good idea, but makes the circuit work.
I decided to build a board to pick up the CC1/CC2 signals and amplify them from a 1.2 V to ~3.3 V high level through a simple non-inverting op-amp with a gain of 2.5. The op-amp is a ST Micro TSV992 dual op-amp with 20 MHz GBW and 10 V/usec slew rate. I still made a mistake picking this particular part, as the datasheet clearly states it is stable for gain >4 only. I might have gotten lucky as I don't see any instability/oscillation in my setup. The part is a standard pinout for a dual op-amp, so the board is still useful and rev 1.1 will use a different op-amp.
Here is the schematic, board and pictures of the setup.
| {gallery}CC Monitor |
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CC Monitor Schematic |
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Bare board front (who has good eyes?) |
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Bare board back |
