LM2671 datasheet(13/26 Pages) NSC

Part #	LM2671

Description	SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator with Features

PDF	26 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

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13 / 26 page

LM2671 Series Buck Regulator Design Procedure (Fixed Output) (Continued)

PROCEDURE (Fixed Output Voltage Version)

EXAMPLE (Fixed Output Voltage Version)

7. Frequency Synchronization (optional)

The LM2671 (oscillator) can be synchronized to run with an

external oscillator, using the sync pin (pin 3). By doing so, the

LM2671 can be operated at higher frequencies than the

standard frequency of 260 kHz. This allows for a reduction in

the size of the inductor and output capacitor.

As shown in the drawing below, a signal applied to a RC filter at

the sync pin causes the device to synchronize to the frequency

of that signal. For a signal with a peak-to-peak amplitude of 3V

or greater,a1k

Ω resistor and a 100 pF capacitor are suitable

values.

7. Frequency Synchronization (optional)

For all applications, usea1k

Ω resistor and a 100 pF capacitor

for the RC filter.

INDUCTOR VALUE SELECTION GUIDES

(For Continuous Mode Operation)

10004229

FIGURE 4. LM2671-3.3

10004230

FIGURE 5. LM2671-5.0

10004231

FIGURE 6. LM2671-12

10004232

FIGURE 7. LM2671-ADJ

LM2671 Datasheet(PDF) 13 Page - National Semiconductor (TI)