Dual RGB LED Driver

The RGB driver has six outputs that can independently drive

2 separate RGB LEDs or six LEDs of any kind. User has

control over the following parameters separately for each

LED:

(PWM brightness control)

(turn-on and turn-off slope)

(output enable control)

The main blinking cycle is controlled with 2-bit CYCLE con-

trol (0.25 / 0.5 / 1.0 / 2.0s).

20080501

RGB PWM Operating Principle

RGB_START is the master enable control for the whole RGB

function. The internal PWM and blinking control can be

disabled by setting the RGB_PWM control LOW. In this case

the individual enable controls can be used to switch outputs

on and off. PWM_LED input can be used for external hard-

ware PWM control.

In the normal PWM mode the R, G and B switches are

controlled in 3 phases (one phase per driver). During each

phase the peak current set by external resistor is driven

through the LED for the time defined by DUTY setting

(0 µs–50 µs). As a time averaged current this means

0%–33% of the peak current. The PWM period is 150 µs and

the pulse frequency is 6.7 kHz in normal mode.

20080506

Normal Mode PWM Waveforms at Different Duty

Settings

In the FLASH mode all the outputs are controlled in one

phase and the PWM period is 50 µs. The time averaged

FLASH mode current is three times the normal mode current

at the same DUTY value.

Blinking can be controlled separately for each output. On

and OFF times determine, when a LED turns on and off

within the blinking cycle. When both ON and OFF are 0, the

LED is on and doesn’t blink. If ON equals OFF but is not 0,

the LED is permanently off.

20080502

Example Blinking Waveforms

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