January 15, 2009
LM5026
Active Clamp Current Mode PWM Controller
General Description
Features
The LM5026 PWM controller contains all of the features nec-
essary to implement power converters utilizing the active
clamp / reset technique with current mode control. With the
active clamp technique, higher efficiencies and greater power
densities can be realized compared to conventional catch
winding or RDC clamp / reset techniques. Two control outputs
are provided, the main power switch control (OUT_A) and the
active clamp switch control (OUT_B). The device can be con-
figured to control either a P-Channel or N-Channel clamp
switch. The main gate driver features a compound configu-
ration, consisting of both MOS and Bipolar devices, providing
superior gate drive characteristics. The LM5026 can be con-
figured to operate with bias voltages over a wide input range
of 8V to 100V. Additional features include programmable
maximum duty cycle, line under-voltage lockout, cycle-by-cy-
cle current limit, hiccup mode fault operation with adjustable
timeout delay, PWM slope compensation, soft-start, 1MHz
capable oscillator with synchronization input / output capabil-
ity, precision reference and thermal shutdown.
Current Mode Control
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Internal 100V Start-up Bias Regulator
3A Compound Main Gate Driver
High Bandwidth Opto-coupler Interface
Programmable Line Under-Voltage Lockout (UVLO) with
Adjustable Hysteresis
Versatile Dual Mode Over-Current Protection with hiccup
delay timer
Programmable Overlap or Deadtime between the Main
and Active Clamp Outputs
Programmable Maximum Duty Cycle Clamp
Programmable Soft-start
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Leading Edge Blanking
Resistor Programmed 1MHz Capable Oscillator
Oscillator Sync I/O Capability
Precision 5V Reference
Packages
TSSOP-16
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LLP-16 (5x5 mm) Thermally Enhanced
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Typical Application Circuit
20147901
Simplified Forward Power Converter with Active Clamp Reset
© 2009 National Semiconductor Corporation
201479
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