Earlier designs I used 74HC595, and HW/firmware designs are perfectly working for it.The problem is they fail frequently & brightness depends on make. So I decided to go for constant current, & as my application is w/o gray scales, I selected TLC5928. :-)
My 595based PCBs are in use since long, So, in same replaced all(8) HC595 by 4No TLC5928 & New PCBs were made. PCBs are made by best CNC facility available in local market.
I use 5V+/-5% SMPS for all circuitry. CPU is AT89S8253 @18.432MHz in 6clock/cycle, transferring data on SPI bus at max speed ~3MHz. Eveen if it's 18MHz, it's in safe region for TLC5928.
Problem faced is: message is readable but random LEDs keep flickering (dim) at some fixed locations. Is that noise because of PADs too close? I have 7-8micron gap at present. (in lay-out, might have become 6 in mfg process.)
Another problem: I tried to use CPU card at 5V & TLC5928 at 3.3V, but then it completely don't work. :'(
Help will be highly appreciated. Thank you.
