HT1632C Led driver help and advice

Hey guys,
I was wondering if you could give me some advice with the HT1632C chip. I’ve learned what I could from the datasheet and various forums online but the information seems to gloss over some noob information I require.

The main goal for me is to drive a 32x8 RGB LED dot matrix (page 17 of attached datasheet). Right now I just have regular red LEDs in there for me to practice and acquire knowledge of how to run the matrix. Could anyone shed some light on the following?

  • There are 2 LED_VSS and LED_VDD pins on the chip. I initially thought that these were input/output for the LED voltages but the LEDs are connected to the ROW and COM pins only. Do the voltages supplied by ROW and COM pins come from the LED_VDD? Why would there be two sets?

  • Can LED_VDD be larger than the 5V stated (which I believe is for the logic circuit)? I don’t want to fry my chip. I want to drive the LEDs with a higher voltage to get maximum brightness - this usually occurs at 20-22mA for the LEDs I have at the moment.

  • If I drive the LEDs at a higher voltage, how would I calculate the resistance required for the ROW pin? There could be anything from 1 to 8 LEDs lit at anyone time.

  • Originally my setup was driving the anodes with the COM lines, I did this because my RGB LEDs are common anode. So the COM would source and the ROWs would sink current like the setup on page 15 of the datasheet. I didn’t use the transistor buffers and the matrix did not light at all. I just want to confirm that if I did include the buffers that the matrix would light and I would not need to edit the software to configure the ROW/COM as source/sink.

My current setup is that of page 13 - ROW source/COM sink - which seems to be the way the chip prefers it (source 70mA/sink 350mA). Should I invest in some common cathode RGB LED or is it worth continuing with common anode and buffering them. Any thoughts on this?

Cheers.

ht1632cv120.pdf (216 KB)