Question on outputs tied into RGB LED matrix

I am designing an RGB LED matrix version of Sure Electronics 2416:

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.

The answer is one you may not want to hear, but the fix is easy.

READ THE DATA SHEET. There is an example of using 3 HT1632s together. When using HT1632s together, only the common terminals of one of the HT1632s are connected to all of the LED arrays. The chips are operated in a slave mode, so all the multiplexing is done automatically.

The fix should be fairly simple. Just cut the traces to the common terminals on the 2nd and 3rd HT1632s, and configure them as master and slaves. The commons to have to supply enough current for all the LEDs that are on. The data sheet shows transistors to do this. Look on pages 15 & 16 of the data sheet dated 6/18/2008.


I wasn't sure if everyone was exactly picturing what I wanted to do so I came up with a picture. This shows the diode approach instead of the transistor buffer (2 parts of transistor and resistor vs 1 part of diode only).

I just wanted to know if you think this would work. Currently I did not have the diodes in place and it caused the 2nd and 3rd HT1632C chips to overheat.


Look at the last link at this post for the picture attachment:

Why the HT1632 with RGB?

How are you going to PWM the channels to get the various colors?

Why not just build it out with TLC5940s and matrix them.

I'm asking because I don't know and was thinking of building a RGB matrix with TLC 5940s so that I could get 30bit color. With the HT1632s, it seems like you're going to have to go to a lot of effort to get any level of blended colors. ????

The HT1632 used in the Sure Electronics 2614 and 0832 displays are obsolete and have been replaced with the HT1632C which besides just providing more output current also uses the ‘RC Master’ ($18) comand now which is a combined command of RC and Master found on the obsolete HT1632.

I have a few samples of the TLC5940 chips but have not done any design work with them. I understand the HT1632C chips more and have working code for my Parallax SX48 but any other micro-controller could also be used. I am awaiting on some IDC connectors from Futurlec to arrive before I can finish the soldering of the boards and write some preliminary coding.

The RGB board is a 24x16 RGB common anode board but with the driver chips I used it is more or less now common cathode which works better with the HT1632C chip. This RGB board is a separate board from the smaller HT1632C board and connected by IDC cables for flexibility. I could also design another TLC5940 control board for the separate 24x16 RGB board in the future also.

The HT1632C has 16 shades of color possible so with RGB I could have up to 4096 colors - which is not 24 bit but still not too bad to start with.

When I get the IDC connectors in, I will try to post some pics for better clarity of what I am trying to do for a concept of operation. Basically it is like an RGB version (3 HT1632C chips used) of the Sure Electronics 2416 board.

More to come.


I'm building a LED matrix projected based on the HT1632. I've been experimenting with the Sure 2416 board & I've got my basic SW working. Now I'm going to lay-out my own matrix board. My only problem is that I can't get hold of samples of the HT1632. I've mailed Holtek & Sure to try and order 10 pieces but got no replies. The HOltek site claims that you can buy direct from them, but only in US. I'm based in Finland ...

Does anyone know of a European distributor for these parts???


I looked at ordering from Holteck from the US. The price per piece is great - a couple dollars. No minimum order. But the handling and shipping fees were a few hundred dollars! Not unreasonable if you want to order hundreds, but not practical to order any small quantity.

I have ordered from their website two times and ordered about 10 or 12 each time and I believe it was about $50 to $60 or so total including shipping and handling charges. Shipping did seem high because the $4.50 or so HT1632C chips had $10 handling + $10 shipping. So $45 for 10 chips has $20 in shipping and handling.

The chips are packed in a plastic case for protection.

Technical question support has been good but slow. I think the chip came from california.