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參數資料
| 型號： | SC4539ULTRT |
| 廠商： | Semtech Corporation |
| 英文描述： | High Effi ciency Boost Converter for up to 6 LEDS |
| 中文描述： | 高艾菲布缺陷升壓多達6個LED轉換器 |
| 文件頁數： | 1/14頁 |
| 文件大小： | 256K |
| 代理商： | SC4539ULTRT |
POWER MANAGEMENT
1
Typical Application Circuit
Applications
White LED Display Backlight Driver
Smartphones and PDAs
Cellular Handsets
MP3 and Portable Media Players
DSC, GPS, Satellite Radio, Game Players
High Efficiency Boost Converter
for up to 6 LEDS
SC4539
SC4539
Features
Input voltage range — 2.8V to 5.5V
Current-mode PWM control — 800kHz
Programmable LED current up to 30mA
Soft-start to reduce in-rush current
PWM dimming — 100Hz to 50kHz
PWM dimming at ISET — Analog and filtered
Over-voltage protection — 25V (max.)
Under-voltage lockout (UVLO)
Thermal shutdown
Shutdown current — <1μA
Ultra-thin package — 2mm x 2mm x 0.6mm
Lead-free package, WEEE and RoHS compliant
Description
The SC4539 is designed to regulate current for a series
chain of white LEDs in LCD backlighting applications
where small size and high efficiency are priorities. This
device integrates an 800kHz current-mode PWM boost
converter and a 30mA programmable low dropout current
sink regulator.
An external resistor sets the LED current up to 30mA.
PWM dimming (100Hz to 50kHz) may be applied directly
to the enable (EN) pin, or dimming can be controlled by
applying an analog signal to the ISET circuit. The boost
circuit can output up to 22V (guaranteed) to drive up to 6
LEDs in series. The current regulator protects against
shorts between the BL and OUT pins and also eliminates
backlight glow during shutdown when using LEDs with
high leakage. Under-voltage lockout and thermal shut-
down provide additional protection. A small external
capacitor and series resistor control soft-start and loop
compensation. Over-voltage detection protects the
SC4539 if the LED pin is floating or shorted to ground.
The SC4539 is available in an MLPD-8 pin 2mm x 2mm x
0.6mm package, with a rated temperature range of -40°C
to +85°C.
OUT
LX
BL
C
IN
2.8 to
5.5V
IN
EN
ISET
GND
COMP
Enable and
PWM dimming
R
ISET
C
COMP
L1
D
C
OUT
R
COMP
September 5, 2007
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