LM5021 Datasheet, PDF (1/15 Pages) National Semiconductor (TI) – AC-DC Current Mode PWM Controller

May 2005
LM5021
AC-DC Current Mode PWM Controller
General Description
The LM5021 off-line pulse width modulation (PWM) control-
ler contains all of the features needed to implement highly
efficient off-line single-ended flyback and forward power con-
verters using current-mode control. The LM5021 features
include an ultra-low (25 µA) start-up current, which mini-
mizes power losses in the high voltage start-up network. A
skip cycle mode reduces power consumption with light loads
for energy conserving applications (ENERGY STAR^®,
CECP, etc.). Additional features include under-voltage lock-
out, cycle-by-cycle current limit, hiccup mode overload pro-
tection, slope compensation, soft-start and oscillator syn-
chronization capability. This high performance 8-pin IC has
total propagation delays less than 100nS and a 1MHz ca-
pable oscillator that is programmed with a single resistor.
Features
n Ultra Low Start-up Current (25 µA maximum)
n Current Mode Control
n Skip Cycle Mode for Low Standby Power
n Single Resistor Programmable Oscillator
n Synchronizable Oscillator
n Adjustable Soft-start
n Integrated 0.7A Peak Gate Driver
n Direct Opto-Coupler Interface
n Maximum Duty Cycle Limiting (80% for LM5021-1 or
50% for LM5021-2)
n Slope Compensation for (LM5021-1 Only)
n Under Voltage Lockout (UVLO) with Hysteresis
n Cycle-by-Cycle Over-Current Protection
n Hiccup Mode for Continuous Overload Protection
n Leading Edge Blanking of Current Sense Signal
n Packages: MSOP-8 or MDIP-8
Simplified Application Diagram
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