LM2672 datasheet(21/36 Pages) TI1

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LM2672

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SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016

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(1)

SM = surface mount, TH = through hole

For this application example, select R1 to be 1 kΩ, 1%. Solve for R2 with Equation 5.

(5)

R2 = 1 kΩ (16.53 − 1) = 15.53 kΩ, closest 1% value is 15.4 kΩ.

R2 = 15.4 kΩ.

10.2.2.2.2

Inductor Selection (L1)

Calculate the inductor Volt × microsecond constant E × T (V × μs) with Equation 6.

where

•

VSAT = internal switch saturation voltage = 0.25 V

•

VD = diode forward voltage drop = 0.5 V

(6)

For this application example, calculate the inductor Volt × microsecond constant (E × T) with Equation 7.

(7)

Use the E × T value from the previous formula and match it with the E × T number on the vertical axis of the

inductor value selection guide in Figure 27. E × T = 21.6 (V × μs).

On the horizontal axis, select the maximum load current (ILOAD(max) = 1 A).

Identify the inductance region intersected by the E × T value and the maximum load current value. Each region is

identified by an inductance value and an inductor code (LXX). From the inductor value selection guide shown in

Figure 27, the inductance region intersected by the 21.6 (V × μs) horizontal line and the 1-A vertical line is 68 μH,

and the inductor code is L30.

Select an appropriate inductor from the four manufacturer's part numbers listed in Table 2. For information on the

different types of inductors, see the inductor selection in the fixed output voltage design procedure. From the

table in Table 2, locate line L30, and select an inductor part number from the list of manufacturers' part numbers.

10.2.2.2.3

Output Capacitor SeIection (COUT)

Select an output capacitor from the capacitor code selection guide in Table 7. Using the inductance value found

in the inductor selection guide, step 1, locate the appropriate capacitor code corresponding to the desired output

voltage. Use the appropriate row of the capacitor code selection guide, in Table 7. For this example, use the 15

to 20 V row. The capacitor code corresponding to an inductance of 68 μH is C20.

Table 7. Capacitor Code Selection Guide

CASE STYLE(1)

OUTPUT

VOLTAGE (V)

INDUCTANCE (μH)

100

150

220

SM and TH

1.21 to 2.5

—

SM and TH

2.5 to 3.75

—

SM and TH

3.75 to 5

—

SM and TH

5 to 6.25

—

SM and TH

6.25 to 7.5

SM and TH

7.5 to 10

C10

C11

C12

C13

SM and TH

10 to 12.5

C14

C11

C12

C13

SM and TH

12.5 to 15

C15

C16

C17

SM and TH

15 to 20

C18

C19

C20

SM and TH

20 to 30

C21

C22

30 to 37

C23

C24

C25

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