CAT4134 Datasheet, PDF (8/12 Pages) Catalyst Semiconductor – 500mA Dual Channel Movie/Flash LED Driver

CAT4134
Device Operation
The device is powered from the input pin VIN. A
switching frequency of 1.2 MHz is used in Movie mode,
when the FLASH input is low. Continuous LED current up
to 50 mA is controlled by the RSET resistor. For higher load
current, the Flash mode is selected by setting the FLASH
input pin high. RFLASH now controls the LED current. In
flash mode, the driver efficiency is kept high even under
high load current by using a lower switching frequency of
900 kHz. In movie mode, the higher frequency of 1.2 MHz
provides a lower noise operation.
Overvoltage Protection (OVP)
To prevent the SW pin voltage from exceeding the internal
switch maximum voltage rating, an overvoltage protection
(OVP) function is supported. The OVP pin allows to set the
Block Diagram
maximum operating voltage on the output VOUT using
external resistors R1 and R2. The resistor ratio sets the
maximum output voltage as shown in the equation below:
ǒ Ǔ ^R1
R2
+
VOUT_MAX
1.2
* 1.2
VOUT_MAX should always be higher than the total LED
forward voltage (SVf) plus 1.2 V. Also VOUT must be less
than SVf + 8 V.
SVf ) 1.2 V t VOUT_MAX t SVf ) 8 V t 16 V
If the overvoltage protection is not needed, then the OVP pin
should be connected to Ground. In that case, the maximum
voltage on the SW pin is set to 17 V.
VIN
VOUT
C_IN
SW
C_OUT
VIN
EN
FLASH
RFLASH
Dual
Frequency
PWM
Controller
PGND
LED1
R1
LED2
OVP
Current
RSET
mux
Setting
2 Current Sink
Regulators
R2
RFLASH
RSET
AGND
Figure 15. Block Diagram
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