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SC4505
High Efficiency Boost Converter
for Backlight/Flash LED Driver
POWER MANAGEMENT
Description
The SC4505 is a high-frequency PWM current-mode step-
up switching regulator with an integrated 2A power tran-
sistor. Its high switching frequency (1MHz) allows the use
of tiny surface-mount external passive components. The
internal switch is rated at 36V which makes the con-
verter ideal for multiple LED series operation with opti-
mal current matching. Two programmable independent
current source structure allows dual panel LED backlight
and flash operation.
Features
Two independent current sources for dual LED strands
with optimal current/light matching. Backlight up to
75mA, Flash up to 125mA
Wide input range from 2.6V to 12V
Adaptive output voltage up to 28V with OVP protec-
tion against open circuit conditions
Low shutdown current (<1
μ
A )
Internal Flash/Torch mode with flash timeout to pro-
tect LEDs
1MHz Fixed Frequency Current-Mode Control
Internal 2A current limit for driving large numbers of
LEDs
Supports PWM Dimming from 50Hz to 50kHz
Internal undervoltage lockout
Small, low profile, thermally enhanced 16-MLPQ pack-
age is fully WEEE and RoHS compliant
Applications
White LED power supplies
Flat screen LCD bias supplies
TFT bias supplies
Dual panel Handset/Liquid Crystal Display Monitor
Portable media players
Digital video cameras
Digital still cameras
The operating frequency of the SC4505 is set at 1MHz.
The selected operating frequency gives the SC4505 de-
sign flexibility for size, cost and efficiency optimization.
The SC4505 is available in thermally enhanced 16-pin
MLPQ package (3x3x0.9mm) with embedded over tem-
perature protection.
Typical Application Circuit
Revision: December 15, 2006
Figure 1. SC4505 Application Circuit for Backlight and Flashlight LED Driver
All Capacitors are Ceramic.
Boost Converter Efficiency vs Input Voltage
(2 String of 3 LEDs @30mA)
77
79
81
83
85
87
2.5
3
3.5
4
4.5
5
Input Voltage (V)
E
C6
12n
C5
12n
(Optional)
FL_TRB
D3
LED
RO2SET
1.54k
0
D6
LED
D2
LED
0
C4
(Optional)
EN_BL
D4
LED
AGND
Power
Ground
0
SC4505
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PGND
PGND
SW
SW
VO
IO2
IO1
COMP
AGND
IO2SET
IO1SET
EN_BL
EN_FL
FL_TRB
FTO
VIN
Analog
Ground
C3
0.33uF
C1
2.2uF
0
C2
2.2u
0
EN_FL
D7
LED
RO1SET
6.98k
LED: SML-LX0603UWD
D1
1
VIN: 2.6V ~ 6.0V
10BQ015
2
L1
IHLP-2525CZ-01-1R5-M-01
D5
LED
R1
1.47k
PGND
0