LM5025 Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – Active Clamp Voltage Mode PWM Controller

March 2004
LM5025
Active Clamp Voltage Mode PWM Controller
General Description
The LM5025 PWM controller contains all of the features
necessary to implement power converters utilizing the Active
Clamp / Reset technique. The device can be configured to
control either a P-Channel clamp switch or an N-Channel
clamp switch. With the active clamp technique, higher effi-
ciencies and greater power densities can be realized com-
pared 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 active clamp output can be configured
for either a guaranteed overlap time (for P-Channel switch
applications) or a guaranteed deadtime (for N_Channel ap-
plications). The two internal compound gate drivers parallel
both MOS and Bipolar devices, providing superior gate drive
characteristics. This controller is designed for high-speed
operation including an oscillator frequency range up to 1MHz
and total PWM and current sense propagation delays less
than 100ns. The LM5025 includes a high-voltage start-up
regulator that operates over a wide input range of 13V to
90V. Additional features include: Line Under Voltage Lockout
(UVLO), softstart, oscillator UP/DOWN sync capability, pre-
cision reference and thermal shutdown.
Features
n Internal Start-up Bias Regulator
n 3A Compound Main Gate Driver
n Programmable Line Under-Voltage Lockout (UVLO) with
Adjustable Hysteresis
n Voltage Mode Control with Feed-Forward
n Adjustable Dual Mode Over-Current Protection
n Programmable Overlap or Deadtime between the Main
and Active Clamp Outputs
n Volt x Second Clamp
n Programmable Soft-start
n Leading Edge Blanking
n Single Resistor Programmable Oscillator
n Oscillator UP / DOWN Sync Capability
n Precision 5V Reference
n Thermal Shutdown
Packages
n TSSOP-16
n LLP-16 (5x5 mm) Thermally Enhanced
Typical Application Circuit
Simplified Active Clamp Forward Power Converter
20086901
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