SNVS309 – MAY 2005
LM27241 Synchronous Buck Regulator Controller for Mobile Systems
Check for Samples: LM27241
•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-
• Notebook Chipset Power Supplies
• Low Output Voltage High Efficiency Buck
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.
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PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
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Copyright © 2005, Texas Instruments Incorporated