LM2674
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SNVS007F –SEPTEMBER 1998–REVISED APRIL 2013
CIN - 22 μF, 50V Tantalum, Sprague “199D Series”
COUT - 47 μF, 25V Tantalum, Sprague “595D Series”
D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F
L1 - 68 μH Sumida #RCR110D-680L
R1 - 1.5 kΩ, 1%
CB - 0.01 μF, 50V Ceramic
For a 5V output, select R2 to be 4.75 kΩ, 1%
where VREF = 1.21V
Use a 1% resistor for best stability.
Figure 23. Standard Test Circuits and Layout Guides Adjustable Output Voltage Versions
LM2674 Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
To simplify the buck regulator design procedure, Texas Instruments
is making available computer design software to be used with the
SIMPLE SWITCHERline of switching regulators.LM267X Made
Simple (version 6.0)is available on Windows® 3.1, NT, or 95
operating systems.
Given:
Given:
VOUT = 5V
VOUT = Regulated Output Voltage (3.3V, 5V, or 12V)
VIN(max) = Maximum DC Input Voltage
ILOAD(max) = Maximum Load Current
1. Inductor Selection (L1)
VIN(max) = 12V
ILOAD(max) = 500 mA
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from Figure 25,
Figure 24 or Figure 26 (output voltages of 3.3V, 5V, or 12V
respectively). For all other voltages, see the design procedure for the
adjustable version.
A. Use the inductor selection guide for the 5V version shown in
Figure 24.
B. From the inductor value selection guide, identify the inductance
region intersected by the Maximum Input Voltage line and the
Maximum Load Current line. Each region is identified by an
inductance value and an inductor code (LXX).
B. From the inductor value selection guide shown in Figure 24, the
inductance region intersected by the 12V horizontal line and the
500mA vertical line is 47 μH, and the inductor code is L13.
C. Select an appropriate inductor from the four manufacturer's part
C. The inductance value required is 47 μH. From Table 1, go to the
numbers listed in Table 1. Each manufacturer makes a different style L13 line and choose an inductor part number from any of the four
of inductor to allow flexibility in meeting various design requirements. manufacturers shown. (In most instances, both through hole and
Listed below are some of the differentiating characteristics of each
manufacturer's inductors:
surface mount inductors are available.)
Schott: ferrite EP core inductors; these have very low leakage
magnetic fields to reduce electro-magnetic interference (EMI) and
are the lowest power loss inductors
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