1 Features

• Efficiency Up to 92%
• Simple and Easy to Design Using Off-The-Shelf External Components
• Resistor Programmable Peak Current Limit Over a Range of 3 A to 7 A
• 120-mΩ DMOS Output Switch
• 3.3-V, 5-V, 12-V Fixed Output and Adjustable
  (1.2 V to 37 V) Versions
• ±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
• Soft-Start Capability
• −40 to 125°C Operating Junction Temperature Range

2 Applications

• Simple-to-Design, High Efficiency (>90%)
  Step-Down Switching Regulators
• Efficient System Preregulator for Linear Voltage Regulators
• Battery Chargers

3 Description

The LM2679 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 LM2679 are available from several manufacturers to greatly simplify the design process.

Other features include the ability to reduce the input surge current at power on by adding a soft-start timing capacitor to gradually turn on the regulator. The LM2679 series also has built-in thermal shutdown and resistor programmable current limit of the power MOSFET switch to protect the device and load circuitry under fault conditions. The output voltage is specified 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