Low Noise, High Efficiency
Regulated White LED Driver
POWER MANAGEMENT
OBJECTIVE -NOVEMBER
Description
Features
9,
SC604A
Very high efficiency over 90% of battery life
The
2000
is a very high efficiency charge pump white
LED driver driver from the mAhXLife
TM
family of products,
optimized for Li-Ion battery applications.
The four (4) LED outputs are current matched for consis-
tent LED brightness. Extremely low battery current is
achieved by automatically reconfiguring the charge pump
to match circuit conditions. Using four LEDs, each at
20mA for a total I
OUT
= 80mA, the SC604A can use less
than 83mA from the supply for most of the battery life.
Patented low noise mode switching circuitry and constant
output current allow the use of extremely small input and
output capacitors.
SC604A
Peak efficiency over 92%
Current regulation for up to 4 LEDs
Digital 3 bit output control logic
Current matching tolerance of ±3% typical
Wide current range per LED [0.5mA - 30mA]
High available total LED current = 4 I
LED
= 120mA
Low Shutdown Current: 1µA typical
Soft start / In-rush current limiting
Short circuit protection
MLP-16 [4x4] Package
Fixed frequency 250kHz
1x, 1.5x and 2x charge pump modes of operation
Applications
Cellular phones
LED backlighting
PDA power supplies
Portable devices
Electronic books
Wireless web appliances
LCD Modules
Typical Application Circuit
Patent Pending
VIN
BATTERY
1µF
VOUT
1µF
SC604A
EN
CTRL0
CTRL1
CTRL2
GND
C1+
1µF
ILED1
ILED2
ILED3
ILED4
ISET
C1-
C2+
1µF
C2-
June 27, 2005
1
United States Patents: 6,504,422, 6,794,926
www.semtech.com
SEMTECH [ SEMTECH CORPORATION ]
