LM5027 Datasheet, PDF (1/35 Pages) National Semiconductor (TI) – Voltage Mode Active Clamp Controller

LM5027
www.ti.com
SNVS620C – AUGUST 2009 – REVISED MARCH 2013
Voltage Mode Active Clamp Controller
Check for Samples: LM5027
FEATURES
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•2 Voltage-Mode Control
• Line Feed-Forward PWM Ramp
• Internal 105V Rated Start-Up Bias Regulator
• Programmable Line Under-Voltage Lockout
(UVLO) with Adjustable Hysteresis
• Versatile Dual Mode Over-Current Protection
• Programmable Volt-Second Llimiter
• Programmable Soft-Start
• Programmable Synchronous Rectifier Soft-
Start and Stop
• Precise 500mV Over-Current Comparator
• Current Sense Leading Edge Blanking
• Programmable Oscillator ith 1 MHz Maximum
Frequency and Synchronization Capability
• Precision 5V Reference
• Programmable Time Delays Between Outputs
PACKAGES
• HTSSOP-20
• WQFN-24
DESCRIPTION
The LM5027 pulse-width modulation (PWM)
controller contains all of the features necessary to
implement power converters utilizing the Active
Clamp / Reset technique. With the active clamp
technique, higher efficiencies and greater power
densities can be realized compared to conventional
catch winding or RDC clamp / reset techniques.
Three control outputs are provided: the main power
switch control (OUTA), the active clamp switch
control (OUTB), and secondary side synchronous
rectifier control (OUTSR). The timing between the
control outputs is adjustable with external resistors
that program internal precision timers. This controller
is designed for high-speed operation including an
oscillator frequency range up to 1 MHz and total
PWM propagation delays less than 50 ns. The
LM5027 includes a high-voltage startup regulator with
a maximum input voltage rating of 105V. Additional
features include Line Under Voltage Lockout (UVLO),
separate soft-start of main and synchronous rectifier
outputs, a timer for hiccup mode current limiting, a
precision reference, and thermal shutdown.
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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