CAT3612 Datasheet, PDF (9/13 Pages) Catalyst Semiconductor – Programmable 300mA Camera Flash LED Driver

Block Diagram
V_IN
CAT3612
C_1− C₁₊
C_2− C₂₊
1x mode (LDO)
1.5x Charge Pump
V_OUT
EN/DIM
1 MHz
Oscillator
Reference
Voltage
Mode Control
LED1
LED2
Current
Setting DAC
Serial
Interface
Registers
LED Channel
Current Regulators
GND
Figure 27. CAT3612 Functional Block Diagram
Basic Operation
At power−up, the CAT3612 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 LEDs 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 (after a fixed of 400 ms) into 1.5x
mode.
In 1.5x mode, the output is approximately equal to 1.5
times the input supply voltage (less any internal voltage
losses).
The above sequence is repeated each and every time the
chip is powered−up or is taken out of shutdown mode (via
EN/DIM pin).
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