LM5025B Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – Active Clamp Voltage Mode PWM Controller

LM5025B
www.ti.com
SNVS354B – JULY 2005 – REVISED MARCH 2013
LM5025B Active Clamp Voltage Mode PWM Controller
Check for Samples: LM5025B
FEATURES
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•2 Internal Start-Up Bias Regulator
• 3A Compound Main Gate Driver
• Programmable Line Under-Voltage Lockout
(UVLO) with Adjustable Hysteresis
• Voltage Mode Control with Feed-Forward
• Adjustable Dual Mode Over-Current Protection
• Programmable Overlap or Deadtime between
the Main and Active Clamp Outputs
• Volt x Second Maximum Duty Cycle Clamp
• Programmable Soft-Start
• Current Sense Leading Edge Blanking
• Single Resistor Programmable Oscillator
• Oscillator Up / Down Sync Capability
• Precision 5V Reference
• Thermal Shutdown
PACKAGES
• TSSOP-16
• WSON-16 (5x5 mm) Thermally Enhanced
DESCRIPTION
The LM5025B is a functional variant of the LM5025
active clamp PWM controller. The functional
differences of the LM5025B are as follows:
• The maximum PWM duty cycle is limited to less
than 75% to reduce voltage stress on the power
MOSFETs.
• The CS2 hiccup mode threshold is increased to
0.5V
• The CS2 filter discharge device is disabled
• The V_CC regulator continues to operate when the
line UVLO is below the threshold of normal
operation
• The V_REF regulator is switched off when the line
UVLO input falls below the operating threshold
• The internal 5kΩ COMP pin pull-up resistor is
removed
The LM5025B 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. Two control outputs are provided, the
main power switch control (OUT_A) and the active
clamp switch control (OUT_B). 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 LM5025B includes a high-voltage start-up
regulator that operates over a wide input range of
13V to 100V. Additional features include: Line Under
Voltage Lockout (UVLO), softstart, oscillator
UP/DOWN sync capability, 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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