LM5025_15 Datasheet, PDF (1/23 Pages) Texas Instruments – Active Clamp Voltage Mode PWM Controller

LM5025
www.ti.com
SNVS265B – DECEMBER 2003 – REVISED MARCH 2013
Active Clamp Voltage Mode PWM Controller
Check for Samples: LM5025
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 Clamp
• Programmable Soft-start
• 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 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 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 active
clamp output can be configured for either a specified
overlap time (for P-Channel switch applications) or a
specified deadtime (for N_Channel applications). 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, precision reference and thermal shutdown.
Typical Application Circuit
VIN
35 - 78V
VOUT
3.3V
LM5025
CS1 CS2
VIN
VCC
UVLO
OUT_A
OUT_B
RAMP
REF ^COMP
Rt
SYNC
TIME
SS
PGND AGND
ERROR
AMP &
ISOLATION
UP/DOWN
SYNC
Figure 1. Simplified Active Clamp Forward Power Converter
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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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