Datasheet

LM2679
www.ti.com SNVS026N –MARCH 2000–REVISED APRIL 2013
SOFTSTART
A capacitor connected from pin 7 to ground allows for a slow turn-on of the switching regulator. The capacitor
sets a time delay to gradually increase the duty cycle of the internal power switch. This can significantly reduce
the amount of surge current required from the input supply during an abrupt application of the input voltage. If
softstart is not required this pin should be left open circuited. Please see the C
SS
SOFTSTART CAPACITOR
section for further information regarding softstart capacitor values.
DAP (VSON PACKAGE)
The Die Attach Pad (DAP) can and should be connected to PCB Ground plane/island. For CAD and assembly
guidelines refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.
DESIGN CONSIDERATIONS
Figure 16. Basic Circuit for Fixed Output Voltage Applications
Figure 17. Basic Circuit for Adjustable Output Voltage Applications
Power supply design using the LM2679 is greatly simplified by using recommended external components. A wide
range of inductors, capacitors and Schottky diodes from several manufacturers have been evaluated for use in
designs that cover the full range of capabilities (input voltage, output voltage and load current) of the LM2679. A
simple design procedure using nomographs and component tables provided in this data sheet leads to a working
design with very little effort. Alternatively, the design software, LM267X Made Simple (version 6.0), can also be
used to provide instant component selection, circuit performance calculations for evaluation, a bill of materials
component list and a circuit schematic.
Copyright © 2000–2013, Texas Instruments Incorporated Submit Documentation Feedback 9
Product Folder Links: LM2679