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SC4812
Current Mode PWM Controller with
Integrated Start-up Circuit and Op Amp
POWER MANAGEMENT
Revision: February 6, 2007
Description Features
Applications
Typical Application Circuit
Wide input range 12V to 90V
High-voltage start-up circuit
Current mode control
Transconductance error amplifier
Leading-edge blanking
Cycle by cycle current limit
Programmable external soft-start
Thermal shutdown
SO-8 package. Fully WEEE and RoHS compliant
The SC4812 is a highly integrated current mode PWM
controller designed for isolated or non-isolated dc-dc con-
verters in telecommunication and data communication
applications. It minimizes the amount of external discrete
components needed and leads to substantial cost and
space saving converter designs.
The circuitry of the SC4812 includes an integrated high
voltage start-up circuit suitable for telecom/industrial
voltage applications. It is disabled during regular opera-
tion and improves efficiency. Current mode control with
leading-edge blanking simplifies control loop design and
internal ramp compensation circuit stabilizes the current
loop when operating above 50% duty cycle. Internal er-
ror amplifier could be used for non-isolated applications.
IP phones, PoE
Telecom isolated converters
Off-line isolated power supplies
Instrumentation power supplies
Battery chargers
C6
C4
R1
R4
C3
C2
C5
R3
Q1
C1
R5
VIN
1
SS/SHDN
4
FB
2
COMP
3
CS
5
GND
6
OUT
7
VCC
8
U1
SC4812
D1
R2
Vin
T1
Vout
