SC1103_05 Datasheet, PDF (1/7 Pages) Semtech Corporation – Asynchronous Voltage Mode PWM Controller for 12V Input

SC1103
Asynchronous Voltage Mode PWM
Controller for 12V Input
POWER MANAGEMENT
Description
The SC1103 is a versatile, low-cost, voltage-mode PWM
controller designed for 12V input DC/DC power supply
applications. A simple, fixed-voltage buck regulator can
be implemented using the SC1103 with a minimum of
external components. Internal level shift and drive
circuitry eliminates the need for an expensive p-channel,
high-side switch. The small device footprint
allows for compact circuit design.
Features
‹ Low cost / small size
‹ Switch mode efficiency up to 95%
‹ 1% reference voltage accuracy
‹ Over current protection
‹ 500mA output drive
‹ 5V to 12V Input power source
‹ Lead free package available. Fully WEEE and RoHS
compliant
SC1103 features include a temperature compensated
voltage reference, triangle wave oscillator, current limit
comparator, frequency shift over-current protection, and
an internally compensated error amplifier. Pulse by pulse
current limiting is implemented by sensing the
differential voltage across an external resistor, or an
appropriately sized PC board trace.
Applications
‹ Pentium® P55 Core Supply
‹ Low Cost Microprocessor Supplies
‹ Peripheral Card Supplies
‹ Industrial Power Supplies
‹ High Density DC/DC Conversion
The SC1103 operates at a fixed frequency of 200kHz,
providing an optimum compromise between efficiency,
external component size, and cost.
Typical Application Circuit
+12V
Q1
IRLR3103
L1
R5
6uH
0.05
GND
C1
1.0
C2
C3
47/16V 47/16V
D2
MBRD1035L
+20V
R1
10
R2
R3
1k
1k
U1
SC1103
C6
R4
1 _VCC
GND ⁸
0.01
2.2
2 _CS(-)
FB ⁷
C4
C5
0.1
0.001
3 _CS(+)
BST ⁶
4 _PGND
C7
DH ⁵
0.1
* NOTE:
R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value
12V to 3.3V @ 10A with “flying capacitor” boost voltage.
Revision: July 28, 2005
1
C8
220/4V
C9
220/4V
C10
220/4V
Vout = 2.5V @ 10A
+
R6
C11
127*see note
1.0
R7
127
GND
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