CAT4109, CAV4109

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4

Output Enable

SHUTDOWN

SHUTDOWN 0 mA

SHUTDOWN 0 mA

0 mA

SHUTDOWN 0 mA

SHUTDOWN 0 mA

LED Current

VIN Quiescent Current

50%

50%

90%

10%

Figure 2. CAT4109/CAV4109 OE Timing

OE Operation

The Output Enable (OE) pin has two primary functions.

When the OE input goes from high to low, all three LED

channels are turned off. If OE remains low for longer than

current” from the supply.

The OE input can be used to adjust the contrast of the RGB

LED by applying an external PWM signal. The device has

a very fast turn−on time (from OE rising to LED on)

allowing “instant on” when dimming LEDs.

When applying PWM signals to the three PWMx inputs

and using the OE pin for dimming, the OE PWM frequency

should be much lower to preserve the color mixing.

Accurate linear dimming on OE is compatible with PWM

frequencies from 100 Hz to 5 kHz for PWM duty cycle

down to 1%. PWM frequencies up to 50 kHz can be

supported for duty cycles greater than 10%.

When performing a combination of low frequencies and

small duty cycles, the device may enter shutdown mode.

This has no effect on the dimming accuracy, because the

To ensure that PWM pulses are recognized, pulse width

a “zero current” shutdown mode after a 4 ms delay (typical)

when OE is held low.