Asynchronous Voltage
Mode PWM Controller
POWER MANAGEMENT
Description
The SC1101 is a versatile, low-cost, voltage-mode PWM
controller designed for low output voltage DC/DC power
supply applications. A simple, fixed-voltage buck
regulator can be implemented using the SC1101 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.
SC1101 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.
The SC1101 operates at a fixed frequency of 200kHz,
providing an optimum compromise between efficiency,
external component size, and cost.
SC1101
Features
Low cost / small size
Switch mode efficiency up to 95%
1% reference voltage accuracy
Over current protection
500mA output drive
SO-8 package
Applications
Pentium® P55 Core Supply
Low Cost Microprocessor Supplies
Peripheral Card Supplies
Industrial Power Supplies
High Density DC/DC Conversion
Typical Application Circuit
Q1
IRLR3103
L1
4uH
R5
0.05
Vout = 2V @ 10A
+
C8
330/2.5V
C9
330/2.5V
C10
330/2.5V
C11
1.0
R6
76.8 *see note
R7
127
+5V
C1
1.0
C2
150/6.3V
C3
150/6.3V
D2
MBRD1035L
GND
GND
+12V
R1
10
R2
1k
R3
1k
1
U1
SC1101
VCC
GND
8
C6
0.01
R4
2.2
2
C4
0.1
C5
0.001
3
CS(-)
FB
7
CS(+)
BST
6
C7
0.1
4
PGND
DH
5
* NOTE:
R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value
Revision: May 25, 2005
1
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