These little jems are serial controlled (i2c) PWM generators, designed by Philips Semiconductor for the purpose of controlling leds. I received samples of both the 9531 and 9533, which contain two separate pwm generators, and either four or eight outputs.

Above is a 9531 mounted to a prototyping adapter so it would go into a breadboard. Original tests with the chips were very interesting. The onboard pwm generator is capable of a wide range of frequencies and a full 8-bit gamut of duty cycles (256 steps). I ended up not liking these chips for a couple of reasons…

The biggest drawback is the chips only contain 2 pwm generators … while this would be great for a dichromatic white lite (yellow + blue), it’s no good for trichromatic (red + blue + green) … so the development would require two chips, and additional logic in the program to figure out which chip controls which color. The programming isn’t that big of deal… but I’m lazy. The second drawback is I couldn’t find anywhere to buy these. I don’t have any venture capital, so I can’t buy them in lots of 1000 from a regional distributor, and the supply houses I normally buy from didn’t have them in stock at the time I was working with them… so they’re on the back burner for now.