PWM Generator Array

Question

I want to use an AVR microcontroller to ultimately control an array of RGB 8-segment displays. The only relatively cost effective RGB 8-segment I could find was here,

but it isn't common anode/cathode; instead, it's slightly more involved in order to reduce pin count from 25 to 14:

There's no reference to an associated driver, so:

• Is this a standard topology, which would have associated driver ICs?

It appears that a PWM must be used to split the cycle in two (a half cycle for each of the two digits on the dual 8-segment display), in which the cycle may be depleted further to dim the associated color (RGB), so:

• If not, is there a means to array a datastream (serial or other) to PWM signal?

Answer 1

Electrically, these are 6 digits by 8 segments.

If you use any well-known method of multiplexing, you can have the usual 8 different colors per segment.

To get intermediate brightness levels, we can imagine 12 logical digits. Multiplexing this way, each physical digit is covered by 2 time slots. If you use a hardware driver, simply connect pairs of digit outputs of the driver.

If the 2 time slots are equally long, you will get 27 different colors. Each LED of a segment can be off, half on, and fully on, resulting in 3 different levels. Taking the power of 3 levels by 3 LEDs results in 27 colors.

If you make one time slot longer than the other, you will get 64 different colors. This case results in 4 different levels per LED, off, 1/3 on, 2/3 on, fully on. 4 to the power of 3 gives 64.

There are caveats:

First, the data sheet reveals only a low maximum peak current. It is just 3 times the maximum continuous current. Please check that you don't source too much, or prepare for early failures.

Second, the perceived brightness of an LED is in general not proportional to the average current. You will need to experiment with the duration of the time slots for the 64-color solution.