CAT3636 Datasheet, PDF (8/14 Pages) Catalyst Semiconductor – 6-Channel Quad-ModeTM Fractional LED Driver in TQFN3x3

Block Diagram
V_IN
CAT3636
C_1− C₁₊
C_2− C₂₊
1x mode (LDO)
1.33x, 1.5x, 2x Charge Pump
V_OUT
EN/SET
0.8, 1.1 MHz
Oscillator
100 kW
Serial
Interface
Reference
Voltage
Registers
Current
Setting DAC
Mode Control
LEDA1
LEDA2
LEDB1
LEDB2
LEDC1
LEDC2
6 Current
Sink Regulators
GND
Figure 20. CAT3636 Functional Block Diagram
Basic Operation
At power−up, the CAT3636 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 (after a fixed delay
time of about 400 ms). In 1.33x mode, the output voltage is
approximately equal to 1.33 times the input supply voltage
(less any internal voltage losses).
If the input voltage is insufficient again or falls to a level
where the regulated currents cannot be maintained, the
device will automatically switch to the 1.5x boost mode
(after a fixed delay time of about 400 ms). In 1.5x mode, the
output is approximately equal to 1.5 times the input supply
voltage (less any internal voltage losses).
If the input voltage fails more or is still insufficient to
drive the LEDs, it will automatically switch again into 2x
mode where the output is approximately equal to 2 times the
input supply voltage (less any internal voltage losses).
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
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