LM5027A_15 Datasheet, PDF (1/35 Pages) Texas Instruments – Voltage Mode Active Clamp Controller

LM5027A
www.ti.com
SNVS642B – APRIL 2010 – REVISED MARCH 2013
Voltage Mode Active Clamp Controller
Check for Samples: LM5027A
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 Limiter and Soft-
Start
• Programmable Synchronous Rectifier Soft-
Start and Stop
• Precise 500mV Over-Current Comparator
• Current Sense Leading Edge Blanking
• Programmable Oscillator With 1 MHz
Maximum Frequency and Synchronization
Capability
• Precision 5V Reference
• Programmable Time Delays Between Outputs
• A 70% Maximum Duty Cycle
DESCRIPTION
The LM5027A is a functional variant of the LM5027
active clamp PWM controller. The functional
difference of the LM5027A is that the maximum duty
cycle of the LM5027A is decreased from 91% to 71%.
In addition, the oscillator timing equation has been
modified.
The LM5027A 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
LM5027A 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.
Packages
• HTSSOP-20
• WQFN-24
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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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