Digging through some datasheets I discovered that I had the MR pin (Master Reset) of the 74HC595 shift registers tied to 5V, so I wouldn't be able to reset it from a microcontroller. I fixed it by widening the data connector to 5 pins and connecting the extra column to MR. I also realized the footprint on the design doesn't match the package of the chips I've ordered; the footprint should've been slightly narrower.
On the cathode board there was no room for the extra pins, so I had to move the power indicator LED to the other side of the board, It's now located near the power connector. I've also added a bunch vias in various places that are connected to GND. This helps the ground fill occupy a larger part of the board. I've also rerouted a couple of traces to make things prettier :)
On the anode board there was a bit more room for the extra pin, but connecting the extra pin took a bit more work. On the anode board the pins are pretty much right next to the pins on the IC. On the cathode board the traces have to cross each other.
One of my colleagues noticed the 100 Ohm resistor between the MOSFETs drain and GND. Ohm's law tells us that a 100 Ohm resistor at 5 Volts will have 0.05 Ampères running through it (I = U/R). It also tells us that there will be 0.25 Watt to handle (P = U^2/R). That doesn't sound like much, but an ordinary 0603 sized resistor is only rated at 1/8th or 1/10th Watt. I don't want to add through hole resistors, so I ordered a bunch of 2512 sized resistors, they're rated at 1 Watt (and easier to find than 1210s). There's plenty of space on the board for the increased footprint, so no problem there. I may be moving the caps to the other side of the board so the MOSFETs have more room for heat dissipation (and electrolytic caps don't like heat much).
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