I am designing an RGB LED matrix version of Sure Electronics 2416: http://www.sureelectronics.net/goods.php?id=979
I got the PCBs made and HT1632C ICs and found that if I solder 2 HT1632C ICs onto the PCB, the LEDs display nothing and the chips get pretty hot. 1 by itself works but 2 or more does nothing.
After troubleshooting all day and going through 2 PCBs and 9 HT1632 chips, I think I know the reason why it is not working and would like some confirmation to that please.
Each HT1632 has 24 cathode outputs. I am using 3 HT1632C ICs for red, green and blue LEDs and 6 RGB LED matrixes (common anode).
Each HT1632 has 16 common anode outputs. Theses 16 common anode outputs are shared by each of the 3 HT1632C ICs 16 common anode outputs.
If they are shared that means they are putting +5vdc on any of these 16 common anode outputs when an LED is turned on. This means that since the 3 HT1632C ICs have their 16 common anode outputs tied together going to the 16 common anode RGB LED matrixes, then that same +5vdc output from one HT1632C chip is actually INPUTing +5vdc onto the other 2 HT1632C ICs 16 common anode outputs.
Does this sound right?
I supose my fix would be to have 16 * 3 diodes (IN914?) on each of the 16 common anode outputs so that the +5vdc does not get fed back into the other 2 HT1632C 16 common anode outputs.
Is there another solution? I spent $200-$300 already on this project for a design flaw. Doh! The HT1632C ICs are fairly small and surface mount so I can't test on a solderless breadboard.