描述 Description

The LM3281 is a high-efficiency low-noise miniature DC-DC converter optimizedfor powering noise-sensitive wireless connectivity chipsets and RF Front EndModules (FEMs) from a single Lithium-Ion cell. The LM3281 is ideal for “alwayson” applications with very low unloaded quiescent current of 16 μA (typ.). The LM3281 steps down an input supply voltage to a fixed output voltage of3.3 V with output current up to 1200 mA. Five different modes of operation areused to optimize efficiency and minimize battery drain. In Pulse WidthModulation (PWM) mode, the device operates at a fixed frequency of 6 MHz whichminimizes RF interference when driving medium-to-heavy loads. At light load, thedevice automatically enters into Economy (ECO) mode with reduced quiescentcurrent. In a low-battery voltage condition, a bypass mode reduces the voltagedropout to 60 mV (typ.) at 600 mA. If very low output voltage ripple is desiredat light loads, the device can also be forced into PWM mode. Shutdown mode turnsthe device off and reduces battery consumption to 0.1 μA (typ.).

特性 Features

? 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 VIN at 300?mA
? Analog Bypass: 60-mV (typ.) Drop-Out at 600 mA
? Low IQ: 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: 2