1. Are you using 180 ohm Rext on each TLC5916?
2. What 5V power supply are you using? Have you measured its output when all the LEDs are on?
3. Do you have a 0.1uF or greater decoupling capacitor local to each TLC5916?
4. Have you tried a lower multiplexing frequency, say 10KHz?
I am indeed using a 180 ohm resistor on the TLC5916s when I run everything at 5 V. The adapter I use for those tests is a 5 V 4 A switching wall adapter; my meter says it's at about 2.2 A when all LEDs are on full brightness.
I do have 0.1uF cap near all TLC5916s (and all other chips). I have a 220uF cap next to the incoming power supply and when I'm using a 12 V power supply I have a 10uF cap next to the voltage regulator (LD1117S50TR) per its data sheet. If you have any other recommendations I would welcome any input.
I haven't tried lower multiplexing frequencies, that will require reworking some of the code, but I will try that out this weekend as well.
btw if you run the setup from 12V then you will dissipate far too much power in the TLC5916s, and I would expect the overtemperature detection will trip in very quickly when you are lighting all the LEDs. Even at 5V, the voltage at their outputs when they are sinking 100mA could be more than 2V, at which the dissipation in each would be 1.6W
Thank you, I hadn't considered that. So far I had just been staying under the 960mA limit of the chips; I hadn't looked at wattage limits.