power supply controller board

Congratulations.

We're in the midst of figuring out why the first-silicon bathymetric lidar chips we've been evaluating don't seem to work. (They aren't really our design, but we've been kibitzing a lot since the very beginning, so we've had a a fair amount of input.)

Looks like the silicon vendor's models for their brand-new integrated APD designs aren't up to snuff. The IC designer's simulations look fine, of course. In any event, we have these 20V APDs that we can't bias above two diode drops because something else starts sucking a lot of current. :(

Razza fraza %&$@#&*!!

However, as Mehitabel used to say at such times, "Toujours gai, toujours gai."

Cheers

Phil Hobbs

We found a mistake on the controller board: an FPGA pin can't do the MOSI thing we wanted. One blue wire, a grim tragedy. Fortunately we can hide it under the microZed.

Congratulations.

It looks like there's some unsuspected silicon connection between the substrate (APD anode, nominally about -18V) and some net called GND_I, which is where ESD fault currents get dumped.

The current isn't going to VSS, VDD, or any of the chip inputs, just GND_I.

The rug only has to be big enough for the amount of dust you actually have. ;)

Cheers

Phil Hobbs