lm22676国半芯片技术文档LM22676 3A SIMPLE SWITCHER, Step-Down Voltage Regulator with Precision Enable November 21, 2008 LM22676 3A SIMPLE SWITCHER, Step-Down Voltage Regulator with Precision Enable General Description The LM22676 series of regulators are monolithic integrated circuits which provide all of the active functions for a stepdown (buck) switching regulator capable of driving up to 3A loads with excellent line and load regulation characteristics. High efficiency (>90%) is obtained through the use of a low ON-resistance N-channel MOSFET. The series consists of a fixed 5V output and an adjustable version. The SIMPLE SWITCHER concept provides for an easy to use complete design using a minimum number of external components and National’s WEBENCH design tool. National’s WEBENCH tool includes features such as external component calculation, electrical simulation, thermal simulation, and Build-It boards for easy design-in. The switching clock frequency is provided by an internal fixed frequency oscillator which operates at 500 kHz. The LM22676 series also has built in thermal shutdown, current limiting and an enable control input that can power down the regulator to a low 25 A quiescent current standby condition. Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Wide input voltage range: 4.5V to 42V Internally compensated voltage mode control Stable with low ESR ceramic capacitors 120 m N-channel MOSFET TO-263 THIN package 100 m N-channel MOSFET PSOP-8 package Output voltage options: -ADJ (outputs as low as 1.285V) -5.0 (output fixed to 5V) ±1.5% feedback reference accuracy Switching frequency of 500 kHz -40°C to 125°C operating junction temperature range Precision enable pin Integrated boot diode Integrated soft-start Fully WEBENCH enabled Step-down and inverting buck-boost applications Package ■ PSOP-8 (Exposed Pad) ■ TO-263 THIN (Exposed Pad) Applications ■ ■ ■ ■ ■ Industrial Control Telecom and Datacom Systems Embedded Systems Automotive Telematics and Body Electronics Conversions from Standard 24V, 12V and 5V Input Rails Simplified Application Schematic 30076501 2008 National Semiconductor Corporation 300765 www.national.com LM22676 Connection Diagrams 30076540 8-Lead