1.3MHz Step-Up Switching
Regulator with 1.4A Switch
POWER MANAGEMENT
Description
The SC4503 is a 1.3MHz current-mode step-up switch-
ing regulator with an integrated 1.4A power transistor.
Its high switching frequency allows the use of tiny sur-
face-mount external passive components. The SC4503
features a combined shutdown and soft-start pin. The
optional soft-start function eliminates high input current
and output overshoot during start-up. The internal com-
pensation network accommodates a wide range of volt-
age conversion ratios. The internal switch is rated at 34V
making the device suitable for high voltage applications
such as Boost and SEPIC.
The SC4503 is available in low-profile 5-lead TSOT-23 and
8-lead 2X2mm MLPD-W packages. The SC4503’s low
shutdown current (< 1μA), high frequency operation and
small size make it suitable for portable applications.
SC4503
Features
Low Saturation Voltage Switch: 260mV at 1.4A
1.3MHz Constant Switching Frequency
Peak Current-mode Control
Internal Compensation
Programmable Soft-Start
Input Voltage Range From 2.5V to 20V
Output Voltage up to 27V
Uses Small Inductors and Ceramic Capacitors
Low Shutdown Current (< 1μA)
Low Profile 5-Lead TSOT-23 and 8-Lead 2X2mm
MLPD-W packages
Fully WEEE and RohS compliant
Applications
Local DC-DC Converters
TFT Bias Supplies
XDSL Power Supplies
Medical Equipment
Digital Cameras
Portable Devices
White LED Drivers
Typical Application Circuit
Typical Application Circuit
D1
10BQ015
1
SW
SC4503
OFF ON
4
SHDN/SS
GND
2
R2
49.9k
FB
3
C4
15pF
R1
432k
C2
4.7µF
VIN
5V
5
IN
C1
1µF
L1
4.7µH
VOUT
12V, 0.5A
Efficiency vs Load Current
95
90
85
Efficiency (%)
1.3MHz
80
75
70
65
60
55
V
OUT
= 12V
C1: Murata GRM188R61A105K
C2: Murata GRM21BR61C475K
L1: Sumida CDC5D23B-4R7
Figure 1(a). 5V to 12V Boost Converter
May 4, 2007
1
50
0.001
0.010
0.100
1.000
Load Current (A)
Figure 1(b). Efficiency of the 5V to 12V Boost Converter
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