FAN5307S18X

FAN5307 High-Efficiency Step-Down DC-DC Converter January 2006 FAN5307 High-Efficiency Step-Down DC-DC Converter Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ General Description The FAN5307, a high efficiency low noise synchronous PWM current mode and Pulse Skip (Power Save) mode DC-DC converter is designed for battery-powered applications. It provides up to 300mA of output current over a wide input range from 2.5V to 5.5V. The output voltage can be either internally fixed or externally adjustable over a wide range of 0.7V to 5.5V VIN by an external voltage divider. Custom output voltages are also available. Contact a Fairchild sales representative for customized output voltage options. At moderate and light loads pulse skipping modulation is used. Dynamic voltage positioning is applied, and the output voltage is shifted 0.8% above nominal value for increased headroom during load transients. At higher loads the system automatically switches to current mode PWM control, operating at 1 MHz. A current mode control loop with fast transient response ensures excellent line and load regulation. In Power Save mode, the quiescent current is reduced to 15µA in order to achieve high efficiency and to ensure long battery life. In shut-down mode, the supply current drops below 1µA. The device is available in 5-lead SOT-23 and 6-lead MLP 3x3mm packages. 95% Efficiency, Synchronous Operation Adjustable Output Voltage Option from 0.7V to VIN 2.5V to 5.5V Input Voltage Range Customized Fixed Output Voltage Options Up to 300mA Output Current Fixed Frequency 1MHz PWM Operation High Efficiency Power Save Mode 100% Duty Cycle Low Dropout Operation Soft Start Dynamic Output Voltage Positioning 15µA Quiescent Current Excellent Load Transient Response 5-Lead SOT-23 Package 6-Lead MLP 3x3mm Package Applications ■ Pocket PCs, PDAs ■ Cell Phones ■ Battery-Powered Portable Devices ■ Digital Cameras ■ Low Power DSP Supplies Typical Application EFFICIENCY vs. LOAD CURRENT VOUT = 1.8V 100 95 90 Efficiency [%] 85 80 75 70 65 0.01 0.1 1 10 100 1000 VIN=3.6V VIN=5.5V VIN=2.5V Load Current [mA] ©2005 Fairchild Semiconductor Corporation 1 www.fairchildsemi.com FAN5307 Rev. 1.0.4 FAN5307 High-Efficiency Step-Down DC-DC Converter Pin Assignment Pin Description 5-Lead SOT-23 Pin No. 1 2 3 4 5 Pin Name VIN GND EN FB LX Pin Description Supply voltage input. Ground. Enable Input. Logic high enables the chip and logic low disables the chip and reduces supply current to