An open-drain port expander for microcontrollers, the Catalyst Semiconductor CAT9552, is aimed at switching and flashing LEDs for advertising and industrial control.

Data arriving through either an I2C or SMBus serial bus sets the state of up to 16 individual LEDs, an oscillator, and two internal timers.

LEDs can be set to 'on', 'off' or 'flash', with the flash rate tied to either of the timers which can be adjusted between 0.172Hz and 44Hz (5.8s to 20ms) and from 0 to 99.6 per cent duty cycle.

"This oscillator and its two timers reduce overall parts count and substantially reduce the I2C bus traffic, which would normally occur if traditional bus expanders were used," said Catalyst. "An added benefit is that outputs not used for controlling LEDs can be used as general-purpose I/Os."

The open-drain outputs are rated at 25mA each, and each LED needs an external current-limiting resistor, or when used as I/O, a pull-up resistor.

The chip comes in a 24 lead SOIC, TSSOP and 4x4mm TQFN with samples now and projected lead-time for production quantities six to eight weeks.

Colour coding LED info
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	Display Trilogy
	Headlight glare
	Phosphorous
	Sensing light
	Grey area
An alternative look at the hues and shades of LED technology