LM2742 datasheet(14/22 Pages) NSC

Part #	LM2742

Description	N-Channel FET Synchronous Buck Regulator Controller for Low Output Voltages

PDF	22 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

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14 / 22 page

Example Circuits (Continued)

This circuit design, detailed in the Design Considerations

section, uses inexpensive aluminum capacitors and off-the-

shelf inductors. It can deliver 10A at better than 85% effi-

ciency. Large bulk capacitance on input and output ensure

stable operation.

The example circuit of Figure 4 has been designed for

minimum component count and overall solution size. A

switching frequency of 600kHz allows the use of small input/

output capacitors and a small inductor. The availability of

separate 5V and 12V supplies (such as those available from

desk-top computer supplies) and the low current further

reduce component count. Using the 12V supply to power the

MOSFET drivers eliminates the bootstrap diode, D1. At low

currents, smaller FETs or dual FETs are often the most

efficient solutions. Here, the Si4826DY, an asymmetric dual

FET in an SO-8 package, yields 92% efficiency at a load of

2A.

20087504

FIGURE 3. 5V to 1.2V, 10A, 300kHz

20087505

FIGURE 4. 5V to 1.8V, 3A, 600kHz

LM2742 Datasheet(PDF) 14 Page - National Semiconductor (TI)