LM3101 Datasheet, PDF (1/20 Pages) National Semiconductor (TI) – Secondary-Side PWM Controller

January 1995
LM3101 Secondary-Side PWM Controller
General Description
The LM3101 is a precision high-speed PWM controller It is
designed to provide secondary-side feedback for offline
Switch-Mode Power Supplies (SMPS) using pulse communi-
cation to the primary-side driver The LM3101 is applicable
in all of the popular converter topologies such as flyback or
forward
The LM3101 combined with its companion LM3001 Primary-
Side Driver forms a regulator chip-set that provides preci-
sion control of offline or other isolated DC DC converters
The communication is realized between the two chips by a
small pulse transformer with one or two turns on its primary
and secondary This type of communication does not intro-
duce any poles or zeroes in the control loop and yields the
fastest possible loop response for the isolated switching
regulator
The secondary-side controller contains a precision 1 242V
reference an error amplifier and a trimmed oscillator which
is programmed with a single resistor The LM3101 can real-
ize voltage current or charge mode control Power supply
monitor features include power-on reset with programmable
delay and overvoltage protection
Features
Y g_{2% precision voltage reference}
Y _{Wide-bandwidth (8 MHz) error amplifier}
Y _{External synchronization}
Y _{Frequency shift during an output short circuit}
Y _{Power-on reset flag with programmable delay}
Y _{Overvoltage crowbar trigger circuit}
Y _{Ramped reference Soft-Start}
Y _{Operation beyond 1 MHz}
Y _{Voltage current or charge mode control}
Typical Applications
Y _{Isolated offline switching power supplies}
Y _{Isolated DC DC power converters}
Y _{Flyback regulator}
Y _{Forward converter}
Block Diagram
C1995 National Semiconductor Corporation TL H 11436
TL H 11436 – 1
RRD-B30M75 Printed in U S A