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PDF SC4502 Data sheet ( Hoja de datos )
| Número de pieza | SC4502 | |
| Descripción | 2MHz Step-Up Switching Regulator | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SC4502 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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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.
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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
SC4502/SC4502H
1.4Amp, 2MHz Step-Up Switching
Regulator with Soft-Start
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
OFF ON 3
10
C3
47nF
10BQ015
8 6,7
IN
SHDN
SW
FB 2
SC4502
SS COMP 1
GND ROSC
R3
4,5 9
R4
C4
C6
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)
-
1.4 59.0 9.53 560
-
2
73.2 5.36 330
22
L1 (µH)
10.5 (Falco D08019)
5.3 (Sumida CDRH5D28)
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
VIN = 5V
VOUT = 12V
0.1 0.2 0.3 0.4
Load Current (A)
0.5
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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1 page  
SC4502/SC4502H
POWER MANAGEMENT
Typical Characteristics
Feedback Voltage vs Temperature
1.3
ROSC vs Switching Frequency
100
1.25
1.2
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VIN = 2V
25ºC
10
1.15
-50 -25
0 25 50 75 100 125
Temperature (ºC)
1
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Frequency (MHz)
Switching Frequency
vs Temperature
1.7
ROSC = 7.68KΩ
1.6
VIN = 12V
1.5
VIN = 2V
1.4
1.3
-50 -25
0 25 50 75 100 125
Temperature (ºC)
Switch Saturation Voltage
vs Switch Current
500
SC4502
400
300
85ºC
200
25ºC
100
0
0 0.5 1 1.5 2
Switch Current (A)
Switch Saturation Voltage
vs Switch Current
500
SC4502H
400
300
85ºC
200
25ºC
100
0
0 0.5 1 1.5 2
Switch Current (A)
Minimum VIN vs Temperature
1.5
1.4
1.3
1.2
1.1
1
-50 -25
0 25 50 75 100 125
Temperature (ºC)
VIN Quiescent Current vs Temperature
1.3
Not Switching
1.2
VIN = 16V
1.1
1
VIN = 2V
0.9
0.8
-50 -25
0 25 50 75 100 125
Temperature (ºC)
VIN Current in Shutdown
vs Input Voltage
50
40
-40ºC
30
125ºC
20
10
0
0
VSHDN = 0
5 10 15
Input Voltage (V)
20
Shutdown Threshold
vs Temperature
1.20
VIN = 2V
1.15
1.10
1.05
1.00
-50 -25
0 25 50 75 100 125
Temperature (ºC)
2005 Semtech Corp.
5
www.semtech.com
5 Page 
POWER MANAGEMENT
Applications Information
IN
SC4502
SC4502H
SHDN
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(a)
VIN
1N4148
IN
SC4502
SC4502H
SHDN
SC4502/SC4502H
IN
SC4502
SC4502H
SHDN
(b)
IN
SC4502
SC4502H
SHDN
(c) (d)
Figure 5. Methods of Driving the Shutdown Pin
(a) Directly Driven from a Logic Gate
(b)
(c)
(d)
Driven from an Open-drain N-channel MOSFET or an Open-Collector
DCorimvebninfrinogmSahuLotdgoicwGnawteithwPitrhoVgrOaH m> mVINed UVLO (See Section Below).
NPN
Transistor
(VOL
<
0.1V)
gate whose VOH is higher than the supply voltage of the
SC4502/SC4502H. The diode clamps the maximum
shutdown pin voltage to one diode voltage above the
input power supply.
Programming Undervoltage Lockout
The SC4502/SC4502H has an internal VIN undervoltage
lockout (UVLO) threshold of 1.4V. The transition from idle
to switching is abrupt but there is no hysteresis. If the
input voltage ramp rate is slow and the input bypass is
limited, then sudden turn on of the power transistor will
cause a dip in the line voltage. Switching will stop if VIN
falls below the internal UVLO threshold. The resulting
output voltage rise may be non-monotonic. The 1.1V
disable threshold of the SC4502/SC4502H can be used
in conjunction with a resistive voltage divider to raise the
UVLO threshold and to add an UVLO hysteresis. Figure 6
shows the scheme. Both VH and VL (the desired upper
and the lower UVLO threshold voltages) are determined
by the 1.1V threshold crossings, VH and VL are therefore:
VH
=
1+
R3
R4
⋅
(1.1V )
VL = VH − VHYS = VH − IHYSR3
Re-arranging,
(10)
R3
=
VHYS
IHYS
(11)
R4
=
R3
VH
1.1V
−1
(12)
2005 Semtech Corp.
11
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11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet SC4502.PDF ] | |
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