深圳市中立信电子科技有限公司

1 Features

1• Efficiency Up to 92%

• Simple and Easy to Design Using Off-the-Shelf

External Components

• 120-mΩ DMOS Output Switch

• 3.3-V, 5-V, and 12-V Fixed Output and Adjustable

(1.2 V to 37 V) Versions

• 50-μA Standby Current When Switched OFF

• ±2% Maximum Output Tolerance Over Full Line

and Load Conditions

• Wide Input Voltage Range: 8 V to 40 V

• 260-kHz Fixed Frequency Internal Oscillator

• −40 to 125°C Operating Junction Temperature

Range

• Create a Custom Design Using the LM2678 With

the WEBENCH® Power Designer

2 Applications

• Simple-to-Design, High Efficiency (>90%) StepDown

Switching Regulators

• Efficient System Preregulator for Linear Voltage

Regulators

• Battery Chargers
3 Description The LM2678 series of regulators are monolithic integrated circuits which provide all of the active functions for a step-down (buck) switching regulator capable of driving up to 5-A loads with excellent line and load regulation characteristics. High efficiency (>90%) is obtained through the use of a low ONresistance DMOS power switch. The series consists of fixed output voltages of 3.3 V, 5 V, and 12 V and an adjustable output version. The SIMPLE SWITCHER® concept provides for a complete design using a minimum number of external components. A high fixed frequency oscillator (260 kHz) allows the use of physically smaller sized components. A family of standard inductors for use with the LM2678 are available from several manufacturers to greatly simplify the design process. The LM2678 series also has built-in thermal shutdown, current limiting, and an ON/OFF control input that can power down the regulator to a low 50- μA quiescent current standby condition. The output voltage is ensured to a ±2% tolerance. The clock frequency is controlled to within a ±11% tolerance.