LM2675M-12 National Semiconductor, LM2675M-12 Datasheet - Page 8

• Manufacturer Part Number: LM2675M-12
• Description: DC/DC Converter IC
• Manufacturer: National Semiconductor

Specifications of LM2675M-12

• Input Voltage: 40V
• Output Current: 1A
• Output Voltage: 12V
• No. Of Pins: 8
• Mounting Type: Surface Mount
• Voltage Regulator Type: Switching
• Output Current Max: 1A
• Peak Reflow Compatible (260 C): No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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To simplify the buck regulator design procedure, National
Semiconductor is making available computer design software
to be used with the SIMPLE SWITCHER line of switching
regulators. LM267X Made Simple version 1.0 is available on
Windows
Given:
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from Figure
4 , Figure 5 or Figure 6 (output voltages of 3.3V, 5V, or 12V
respectively). For all other voltages, see the design procedure
for the adjustable version.
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).
Test Circuit and Layout Guidelines
C
C
D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F
L1 - 68 µH Sumida # RCR110D-680L
R1 - 1.5 k , 1%
C
For a 5V output, select R2 to be 4.75 k , 1%
where V
Use a 1% resistor for best stability.
LM2675 Series Buck Regulator Design Procedure (Fixed Output)
V
V
I
LOAD
IN
OUT
B
OUT
IN
- 0.01 µF, 50V Ceramic
- 22 µF, 50V Tantalum, Sprague “199D Series”
(max) = Maximum DC Input Voltage
- 47 µF, 25V Tantalum, Sprague “595D Series”
(max) = Maximum Load Current
PROCEDURE (Fixed Output Voltage Version)
= Regulated Output Voltage (3.3V, 5V, or 12V)
®
REF
3.1, NT, or 95 operating systems.
= 1.21V
FIGURE 3. Standard Test Circuits and Layout Guides
Adjustable Output Voltage Versions
(Continued)
8
Given:
1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown
in Figure 5 .
B. From the inductor value selection guide shown in Figure 5 ,
the inductance region intersected by the 12V horizontal line
and the 1A vertical line is 33 µH, and the inductor code is L23.
V
V
I
LOAD
OUT
IN
(max) = 12V
(max) = 1A
= 5V
EXAMPLE (Fixed Output Voltage Version)
DS012803-23