CAT3604V_14 Datasheet, PDF (10/13 Pages) ON Semiconductor – 4-Channel LED Driver

Block Diagram
V_IN VIN
CAT3604V
C_1− C₁₊
C_2− C₂₊
1x mode (LDO)
1.33x, 1.5x, 2x Charge Pump
VOUT
EN
RSET
1, 1.3 MHz
Oscillator
Mode Control
Reference
Voltage
Current
Setting
LED1
LED2
LED3
LED4
LED Channel
Current Regulators
GND
Figure 25. CAT3604V Functional Block Diagram
Basic Operation
At power−up, the CAT3604V 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).
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 500 mV
The EN pin enables and disables the device. The LED
driver enters a “zero current” shutdown mode if EN is held
low for 1.5 ms or more.
As soon as the EN input goes low, all LED channels are
instantly disabled, where the LED current is set to zero. As
long as the CAT3604V is not in shutdown mode, the LEDs
turn on as soon as the EN goes high.
Unused LED Channels
For applications not requiring all the channels, it is
recommended to connect the unused LED pins directly to
VOUT (see Figure 26).
1 mF
1 mF
V_IN
C_IN
1 mF
ON _OFF
R_SET
C1+ C1− C2+ C2−
VIN
VOUT
CAT3604V
EN
RSET
GND
LED1
LED2
LED3
LED4
C_OUT
1 mF
LED Current Selection
The LED current is set to by the external resistor RSET as
follows:
LED current + 132
0.6 V
R_SET
Figure 26. Application with 3 LEDs
Protection Mode
If an LED is disconnected, the device senses that, run the
diagnostics, then ignores that channel and goes back to the
most effective mode. When all LEDs are disconnected, the
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