Product Summary

The LM2678 series of regulators are monolithic integratedcircuits which provide all of the active functions for astep-down (buck) switching regulator capable of driving up to5A loads with excellent line and load regulation characteris-tics. High efficiency (>90%) is obtained through the use of alow ON-resistance DMOS power switch. The series consistsof fixed output voltages of 3.3V, 5V and 12V and an adjust-able output version.The SIMPLE SWITCHER concept provides for a completedesign using a minimum number of external components. Ahigh fixed frequency oscillator (260KHz) allows the use ofphysically smaller sized components. A family of standard in-ductors for use with the LM2678 are available from severalmanufacturers to greatly simplify the design process.The LM2678 series also has built in thermal shutdown, cur-rent limiting and an ON/OFF control input that can powerdown the regulator to a low 50μA quiescent current standbycondition. The output voltage is guaranteed to a ±2% toler-ance. The clock frequency is controlled to within a ±11% tol-erance.

Parametrics

Absolute Maximum Ratings :
If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.
(1)Input Supply Voltage:45V;
(2)ON/OFF Pin Voltage:-0.1V to 6V;
(3)Switch Voltage to Ground:-1V to VIN;
(4)Boost Pin Voltage:VSW +8V;
(5)Feedback Pin Voltage:-0.3V to 14V;
(6)Power Dissipation:Internally Limited;
(7)ESD:2 kV;
(8)Storage Temperature Range:-65℃ to 150℃;
(9)Soldering Temperature,Wave:4 sec, 260℃;Infrared:10 sec, 240℃;Vapor Phase:75 sec, 219℃

Features

(1)Efficiency up to 92%;
(2)Simple and easy to design with (using off-the-shelf external components);
(3)120 mΩ DMOS output switch;
(4)3.3V, 5V and 12V fixed output and adjustable (1.2V to 37V ) versions;
(5)50μA standby current when switched OFF;
(6)±2%maximum output tolerance over full line and load conditions;
(7)Wide input voltage range: 8V to 40V;
(8)260 KHz fixed frequency internal oscillator;
(9)-40 to +125℃ operating junction temperature range

Diagrams

<IMG border=0 src="http://www.seekic.com/uploadfile/ic-mfg/2012841137173.jpg">

Image Part No Mfg Description Data Sheet Download Pricing
(USD)		 Quantity
LM2678S-3.3
LM2678S-3.3
National Semiconductor (TI)
Switching Converters, Regulators & Controllers
Data Sheet
0-135: $3.29
135-270: $3.03
270-540: $2.76
540-1035: $2.32
LM2678S-3.3/NOPB
LM2678S-3.3/NOPB
National Semiconductor (TI)
Switching Converters, Regulators & Controllers HIGH EFF 5A STEP- DOWN VLTG REG
Data Sheet
0-1: $4.45
1-25: $3.65
25-100: $3.29
100-250: $3.03