OBSOLETE
LM27241
www.ti.com
SNVS309 – MAY 2005
LM27241 Synchronous Buck Regulator Controller for Mobile Systems
Check for Samples: LM27241
FEATURES
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•2 Input voltage range from 5.5V to 28V
• Forced-PWM or Pulse-skip modes
• Lossless bottom-side FET current sensing
• Adaptive duty cycle clamping
• High current N-channel FET drivers
• Low shutdown supply currents
• Reference voltage accurate to within ±1.5%
• Output voltage adjustable down to 0.6V
• Power Good flag and Chip Enable
• Under-voltage lockout
• Over-voltage/Under-voltage protection
• Soft-start and Soft-shutdown
• Switching frequency adjustable 200kHz-
500kHz
APPLICATIONS
• Notebook Chipset Power Supplies
• Low Output Voltage High Efficiency Buck
Regulators
DESCRIPTION
The LM27241 is an adjustable 200kHz-500kHz single channel voltage-mode controlled high-speed synchronous
buck regulator controller. It is ideally suited for battery powered applications such as laptop and notebook
computers. The LM27241 requires only N-channel FETs for both the upper and lower positions of the
synchronous stage. It features line feedforward to improve the response to input transients. At very light loads,
the user can choose between the high-efficiency Pulse-skip mode or the constant frequency Forced-PWM mode.
Lossless current limiting without the use of external sense resistor is made possible by sensing the voltage drop
across the bottom FET. A unique adaptive duty cycle clamping technique is incorporated to significantly reduce
peak currents under abnormal load conditions. The input voltage range is 5.5V to 28V while the output voltage is
adjustable down to 0.6V.
Standard supervisory and control features include soft-start, power good, output under-voltage and over-voltage
protection, under-voltage lockout, soft-shutdown and enable.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
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.
Copyright © 2005, Texas Instruments Incorporated
