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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SC4503
POWER MANAGEMENT
Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the
Electrical Characteristics section is not recommended.
Parameter
Supply Voltage
SW Voltage
FB Voltages
SHDN/SS Voltage
Thermal Resistance Junction to Ambient (TSOT - 23)
Thermal Resistance Junction to Ambient (2X2 mm MLPD-W)
Maximum Junction Temperature
Storage Temperature Range
Lead Temperature (Soldering)10 sec (TSOT - 23)
Peak IR Reflow Temperature (2X2mm MLPD-W)
ESD Rating (Human Body Model)
Symbol
V
IN
V
SW
V
FB
V
SHDN
θ
JA
θ
JA
T
J
T
STG
T
LEAD
T
IR
ESD
Maximum
-0.3 to 20
-0.3 to 34
-0.3 to V
IN
+0.3
-0.3 to V
IN
+1
191*
78*
150
-65 to +150
Units
V
°C/W
°C/W
°C
260
260
2000
V
*Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad as per JESD51 standards.
Electrical Characteristics
Unless specified: V
IN
= V
SHDN/SS
= 3V, -40°C < T
A
= T
J
< 85°C
Parameter
Under-Voltage Lockout Threshold
Maximum Operating Voltage
Feedback Voltage
Feedback Line Voltage Regulation
FB Pin Bias Current
Switching Frequency
Minimum Duty Cycle
Maximum Duty Cycle
Switch Current Limit
Switch Saturation Voltage
Switch Leakage Current
V
IN
Quiescent Supply Current
V
IN
Supply Current in Shutdown
2007 Semtech Corp.
Conditions
Min
Typ
2.2
Max
2.5
20
Units
V
1.225
2.5V < V
IN
< 20V
1.250
0.02
-25
1.275
%/V
-50
1.55
0
%
nA
MHz
1.15
1.30
86
1.4
I
SW
= 1.4A
V
SW
= 5V
V
SHDN/SS
= 2V, V
FB
= 1.5V (not switching)
V
SHDN/SS
= 0
2
90
1.9
260
0.01
0.8
0.01
2.5
430
1
1.1
1
A
mV
µA
mA
µA
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SC4503
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: V
IN
= V
SHDN/SS
= 3V, -40°C < T
A
= T
J
< 85°C
Parameter
SHDN/SS Switching Threshold
Shutdown Input High Voltage
Shutdown Input Low Voltage
Conditions
V
FB
= 0V
Min
Typ
1.4
Max
Units
V
V
2
0.4
V
SHDN/SS
= 2V
22
20
50
45
0.1
155
°C
10
µA
SHDN/SS Pin Bias Current
V
SHDN/SS
= 1.8V
V
SHDN/SS
= 0V
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Pin Configuration - TSOT - 23
Top View
SW
GND
FB
1
2
3
4
SHDN/SS
5
IN
Ordering Information
Device
(1,2)
SC4503TSKTRT
SC4503EVB
Top Mark
BH00
Package
TSOT-23
Evaluation Board
5-LEAD TSOT-23
Notes:
(1) Available in tape and reel only. A reel contains 3,000 devices.
(2) Available in lead-free package only. Device is WEEE and
RoHS compliant.
Pin Descriptions - TSOT -23
Pin
1
2
3
Pin Name
SW
GND
FB
Pin Functions
Collector of the internal power transistor. Connect to the boost inductor and the freewheeling
diode. The maximum switching voltage spike at this pin should be limited to 34V.
Ground. Tie to ground plane.
The inverting input of the error amplifier. Tie to an external resistive divider to set the output volt-
age.
4
Shutdown and Soft-start Pin. Pulling this pin below 0.4 shuts down the converter. Applying more
than 2V at this pin enables the SC4503. An external resistor and an external capacitor con-
nected to this pin soft-start the switching regulator. The SC4503 will try to pull the SHDN/SS pin
SHDN/SS below its 1.4V switching threshold regardless of the external circuit attached to the pin if VIN
is below the under-voltage lockout threshold. Tie this pin through an optional resistor to IN or
to the output of a controlling logic gate if soft-start is not used. See Applications Information for
more details.
IN
Power Supply Pin. Bypassed with capacitor close to the pin.
3
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5
2007 Semtech Corp.
SC4503
POWER MANAGEMENT
Pin Configuration - 2mm X 2mm MLPD
Top View
Ordering Information
Device
(1,2)
Top Mark
E00
Package
2mmX2mm
MLPD-W
SW
1
8
NC
SC4503WLTRT
SC4503_MLPD EVB
SW
2
7
GND
Evaluation Board
IN
3
6
GND
SHDN/SS
4
5
FB
Notes:
(1) Available in tape and reel only. A reel contains 3,000 devices.
(2) Available in lead-free package only. Device is WEEE and
RoHS compliant.
8-LEAD 2X2mm MLPD-W
Pin Descriptions - 2X2mm MLPD-W
Pin
1,2
Pin Name
SW
Pin Functions
Collector of the internal power transistor. Connect to the boost inductor and the free-
wheeling diode. The maximum switching voltage spike at this pin should be limited to
34V.
Power Supply Pin. Bypassed with capacitor close to the pin.
Shutdown and Soft-start Pin. Pulling this pin below 0.4 shuts down the converter. Apply-
ing more than 2V at this pin enables the SC4503. An external resistor and an external
capacitor connected to this pin soft-start the switching regulator. The SC4503 will try
to pull the SHDN/SS pin below its 1.4V switching threshold regardless of the external
circuit attached to the pin if VIN is below the under-voltage lockout threshold. Tie this pin
through an optional resistor to IN or to the output of a controlling logic gate if soft-start is
not used. See Applications Information for more details.
The inverting input of the error amplifier. Tie to an external resistive divider to set the
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