1 Features
1• Operates from a Single Li-Ion Cell (3 V to 5.5 V)
• 6-MHz (typ.) PWM Switching Frequency
• Fixed Output Voltage: 3.3 V
• Up to 1.2-A Maximum Load Capability
• High Efficiency: 94% (typ.) with 3.8-V V IN at
300 mA
• Analog Bypass: 60-mV (typ.) Drop-Out at 600 mA
• Low I Q: 16 μA typical, 25 μA maximum
• Automatic ECO/PWM/Bypass Mode Change
• Forced PWM Mode for Low Output-Voltage Ripple
• Soft-Start Limits Input Current on Start-Up
• Current Overload Protection
• Thermal Overload Protection
• Small Total Solution Size: < 7.5 mm2

2 Applications
• WLAN, WiFi Station Devices
• WiFi RF PC Cards
• Battery-Powered RF Devices

3 Description
The LM3281 is a high-efficiency low-noise miniature
DC-DC converter optimized for powering noise- sensitive wireless connectivity chipsets and RF Front
End Modules (FEMs) from a single Lithium-Ion cell.
The LM3281 is ideal for “always on” applications with
very low unloaded quiescent current of 16 μA (typ.).
The LM3281 steps down an input supply voltage to a
fixed output voltage of 3.3 V with output current up to
1200 mA. Five different modes of operation are used
to optimize efficiency and minimize battery drain. In
Pulse Width Modulation (PWM) mode, the device
operates at a fixed frequency of 6 MHz which
minimizes RF interference when driving medium-to- heavy loads. At light load, the device automatically
enters into Economy (ECO) mode with reduced
quiescent current. In a low-battery voltage condition,
a bypass mode reduces the voltage dropout to 60 mV
(typ.) at 600 mA. If very low output voltage ripple is
desired at light loads, the device can also be forced into PWM mode. Shutdown mode turns the device off
and reduces battery consumption to 0.1 μA (typ.).