cat4139 Catalyst Semiconductor, cat4139 Datasheet - Page 8

• Manufacturer Part Number: cat4139
• Description: 22v High Current Boost White Led Driver
• Manufacturer: Catalyst Semiconductor

CAT4139
OPEN LED PROTECTION
In the event of an “Open LED” fault condition, the
CAT4139 will continue to boost the output voltage
with maximum power until the output voltage
reaches approximately 24V. Once the output
exceeds this level, the internal circuitry immediately
places the device into a very low power mode
where the total input power is limited to about 6mW
(about 1.6mA input current with a 3.6V supply). The
SW pin clamps at a voltage below its maximum
rating of 40V. There is no need to use an external
zener diode between VOUT and the FB pin. A 35V
rated C2 capacitor is required to prevent any
overvoltage damage in the open LED condition.
Doc. No. MD-5032 Rev. A
V
IN
4.7µF
OFF
C1
2.5
2.0
1.5
1.0
Open LED Protection Circuit
Open LED Supply Current
ON
3.0
3.5
INPUT VOLTAGE [V]
SHDN
VIN
22µH
CAT4139
L
GND
4.0
(Central CMSH05-4)
SW
FB
4.5
Schottky 40V
D
5.0
5.5
V
15Ω
R1
1µF
OUT
C2
8
Open LED Disconnect and Reconnect
35
30
25
20
15
Open LED Output Voltage
3.0
Open LED Disconnect
3.5
INPUT VOLTAGE [V]
4.0
Characteristics subject to change without notice
4.5
© Catalyst Semiconductor, Inc.
5.0
5.5