CAT3649 Datasheet, PDF (4/14 Pages) ON Semiconductor – 6-Channel Quad-Mode LED Driver with 32 Dimming Levels & PWM

CAT3649
Figure 3. Functional Block Diagram
Basic Operation
At power−up, the CAT3649 starts operating in 1x mode
where the output will be approximately equal to the input
supply voltage (less any internal voltage losses). If the
output voltage is sufficient to regulate all LED currents, the
device remains in 1x operating mode.
If the input voltage is insufficient or falls to a level where
the regulated currents cannot be maintained, the device
automatically switches into 1.33x mode. In 1.33x mode, the
output voltage is approximately equal to 1.33 times the input
supply voltage (less any internal voltage losses).
This sequence repeats in the 1.33x and 1.5x mode until the
driver enters the 2x mode. In 1.5x mode, the output voltage
is approximately equal to 1.5 times the input supply voltage.
While in 2x mode, the output is approximately equal to 2
times the input supply voltage.
If the device detects a sufficient input voltage is present to
drive all LED currents in 1x mode, it will change
automatically back to 1x mode. This only applies for
changing back to the 1x mode. The difference between the
input voltage when exiting 1x mode and returning to 1x
mode is called the 1x mode transition hysteresis (V_HYS) and
is about 300 mV.
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