SC4502 Datasheet, PDF (1/19 Pages) Semtech Corporation – 1.4Amp, 2MHz Step-Up Switching Regulator with Soft-Start

SC4502/SC4502H
1.4Amp, 2MHz Step-Up Switching
Regulator with Soft-Start
POWER MANAGEMENT
Description
The SC4502/SC4502H is a high-frequency current-mode
step-up switching regulator with an integrated 1.4A
power transistor. Its high switching frequency (program-
mable up to 2MHz) allows the use of tiny surface-mount
external passive components. Programmable soft-start
eliminates high inrush current during start-up. The inter-
nal switch is rated at 32V (40V for the SC4502H) mak-
ing the converter suitable for high voltage applications
such as Boost, SEPIC and Flyback.
The operating frequency of the SC4502/SC4502H can
be set with an external resistor. The ability to set the
operating frequency gives the SC4502/SC4502H design
flexibilities. A dedicated COMP pin allows optimization of
the loop response. The SC4502/SC4502H is available
in thermally enhanced 10-pin MLPD package.
Typical Application Circuit
Features
‹ Low saturation voltage switch: 210mV
(250mV for the SC4502H)
‹ Constant switching frequency current-mode control
‹ Programmable switching frequency up to 2MHz
‹ Soft-Start function
‹ Input voltage ranges from 1.4V to 16V
‹ Output voltage up to 32V (40V for the SC4502H)
‹ Low shutdown current
‹ Adjustable undervoltage lockout threshold
‹ Small low-profile thermally enhanced lead free
package. This product is fully WEEE and RoHS
compliant.
Applications
‹ Flat screen LCD bias supplies
‹ TFT bias supplies
‹ XDSL power supplies
‹ Medical equipment
‹ Digital video cameras
‹ Portables devices
‹ White LED power supplies
VIN
5V
C1
2.2µF
L1
D1
10BQ015
8
6,7
IN
OFF ON ³ _SHDN
SW
FB ²
SC4502
10 _SS
COMP ¹
C3
47nF
GND
4,5
ROSC
9
R4
R3
C6
C4
R1
866K
R2
100K
VOUT
12V
C2
10µF
All Capacitors are Ceramic.
f (MHz) R₃ (KΩ) R₄ (KΩ)
0.7 33.2 23.7
C₄ (pF)
1500
C₆ (pF)
-
L₁ (µH)
10.5 (Falco D08019)
1.4 59.0 9.53 560
-
5.3 (Sumida CDRH5D28)
2
73.2 5.36 330
22
3.3 (Coilcraft DO1813P)
Figure 1(a). 5V to 12V Boost Converter.
Efficie ncy
95
10.5µH, 700KHz
90
5.3µH, 1.4MHz
85
80
75
3.3µH, 2MHz
70
65
60
55
50
0.0
V_IN = 5V
V_OUT = 12V
0.1 0.2 0.3 0.4 0.5
Load Current (A)
Figure 1(b). Efficiencies of 5V to 12V Boost Converters at
700KHz, 1.4MHz and 2MHz.
Revision: July 25, 2005
1
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