1 Features

• 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%) Step-Down 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 ON-resistance 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.

1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application