1 Features
1• Ultrahigh Efficiency up to 97%
• High-Efficiency Over a 1.5-A to 1.5-mA Load
Range
• 4-V to 14-V Input Voltage Range
• 1.8-V, 2.5-V, 3.3-V, or ADJ Output Voltage
• Internal MOSFET Switch With Low RDS(on) of
75 mΩ
• 300-kHz Fixed Frequency Internal Oscillator
• 7-μA Shutdown Current
• Patented Current Sensing for Current Mode
Control
• Input Undervoltage Lockout
• Adjustable Soft-Start
• Current Limit and Thermal Shutdown
• 16-Pin TSSOP Package

2 Applications
• Personal Digital Assistants (PDAs)
• Computer Peripherals
• Battery-Powered Devices
• Handheld Scanners
• High-Efficiency 5-V Conversion

3 Description
The LM2651 switching regulator provides high-
efficiency power conversion over a 100:1 load range (1.5 A to 15 mA). This feature makes the LM2651 an
ideal fit in battery-powered applications that demand
long battery life in both run and standby modes.
Synchronous rectification is used to achieve up to
97% efficiency. At light loads, the LM2651 enters a
low power hysteretic or sleep mode to maintain high
efficiency. In many applications, the efficiency still
exceeds 80% at 15-mA load. A shutdown pin is
available to disable the LM2651 and reduce the
supply current to less than 10 μA.
The LM2651 contains a patented current sensing
circuitry for current mode control. This feature
eliminates the external current sensing resistor
required by other current-mode DC-DC converters.
The LM2651 has a 300-kHz fixed frequency internal
oscillator. The high oscillator frequency allows the
use of extremely small, low-profile components.
A programmable soft-start feature limits current
surges from the input power supply at start-up and provides a simple means of sequencing multiple
power supplies.
Other protection features include input undervoltage
lockout, current limiting, and thermal shutdown.