LM2647

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SNVS210E – MAY 2004 – REVISED JUNE 2005

LM2647 Dual Synchronous Buck Regulator Controller

Check for Samples: LM2647

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FEATURES

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Power Good flag and Chip Enable

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Under-voltage lockout

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Input voltage range from 5.5V to 28V

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Over-voltage/Under-voltage protection

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Synchronous dual-channel Interleaved

switching

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Soft-start and Soft-shutdown

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Forced-PWM or Pulse-skip modes

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Switching frequency adjustable 200kHz-

500kHz

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Lossless bottom-side FET current sensing

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Adaptive duty cycle clamping

APPLICATIONS

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High current N-channel FET drivers

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Notebook Chipset Power Supplies

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Low shutdown supply currents

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Low Output Voltage High-Efficiency Buck

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Reference voltage accurate to within ±1.5%

Regulators

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Output voltage adjustable down to 0.6V

DESCRIPTION

The LM2647 is an adjustable 200-500kHz dual channel voltage-mode controlled high-speed synchronous buck

regulator controller ideally suited for battery powered applications such as laptop and notebook computers. The

LM2647 requires only N-channel FETs for both the upper and lower positions of each 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 resistors 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 two independently programmable outputs switch 180° out of phase

(interleaved switching) to reduce the input capacitor and filter requirements. The input voltage range is 5.5V to

28V while the output voltages are 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.

Copyright © 2004–2005, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.