1FEATURES
2• 300 kHz Fixed-Frequency Switching
• Switching Synchronization with an External
Signal up to 400 kHz
• Optional Pulse-Skipping Mode
• Adjustable Secondary Feedback
• Input Undervoltage Lockout
• Output Undervoltage Shutdown Protection
• Output Overvoltage Shutdown Protection
• Programmable Soft-Start (Each Controller)
• 5V, 50 mA Linear Regulator Output
• Precision 2.5V Reference Output
• 28-pin TSSOP

APPLICATIONS
• Notebook and Subnotebook Computers
• Wireless Data Terminals
• Battery-Powered Instruments

KEY SPECIFICATIONS
• 96 % Efficient
• 5.5 – 30 V Input Range
• Dual Outputs Adjustable from 2.2 – 8 V
• 0.5 % Typical Load Regulation Error
• 0.002 %/V Typical Line Regulation Error

DESCRIPTION
The LM2641 is a dual step-down power supply
controller intended for application in notebook
personal computers and other battery-powered
equipment.
Fixed-frequency synchronous drive of logic-level N-
channel power MOSFETs is combined with an
optional pulse-skipping mode to achieve ultra efficient
power conversion over a 1000:1 load current range.
The pulse-skipping mode can be disabled in favor of
fixed-frequency operation regardless of the load
current level.
High DC gain and current-mode feedback control
assure excellent line and load regulation and a wide
loop bandwidth for fast response to dynamic loads.
An internal oscillator fixes the switching frequency at
300 kHz. Optionally, switching can be synchronized
to an external clock running as fast as 400 kHz.
An optional soft-start feature limits current surges
from the input power supply at start up and provides a simple means of start-up sequencing.
Logic-level inputs allow the controllers to be turned
ON and OFF separately.