LM2671N-ADJ National Semiconductor, LM2671N-ADJ Datasheet - Page 16

• Manufacturer Part Number: LM2671N-ADJ
• Description: Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM2671N-ADJ

• Output Current: 500mA
• No. Of Pins: 8
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• Mounting Type: Through Hole
• Package / Case: 8 Lead
• 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 is available on Windows
3.1, NT, or 95 operating systems.
Given:
1. Programming Output Voltage (Selecting R
shown in Figure 3 )
Use the following formula to select the appropriate resistor
values.
where V
Select a value for R
resistor values minimize noise pickup in the sensitive feedback
pin. (For the lowest temperature coefficient and the best
stability with time, use 1% metal film resistors.)
2. Inductor Selection (L1)
A. Calculate the inductor Volt • microsecond constant E • T
(V • µs), from the following formula:
LM2671 Series Buck Regulator Design Procedure (Fixed Output)
AVX TPS
Sprague 594D
LM2671 Series Buck Regulator Design Procedure (Adjustable Output)
V
V
I
F = Switching Frequency (Fixed at a nominal 260 kHz).
LOAD
OUT
IN
PROCEDURE (Adjustable Output Voltage Version)
(max) = Maximum Input Voltage
(max) = Maximum Load Current
= Regulated Output Voltage
REF
Application Voltage
Application Voltage
= 1.21V
Recommended
Recommended
1
3.3
2.5
3.3
between 240
5
5
8
+85˚C Rating
+85˚C Rating
FIGURE 15. Recommended Application Voltage for AVX TPS and
Sprague 594D Tantalum Chip Capacitors Derated for 85˚C.
and 1.5 k . The lower
Voltage
Voltage
Rating
Rating
6.3
6.3
10
10
16
4
1
and R
2
, as
16
Given:
1. Programming Output Voltage (Selecting R
shown in Figure 3 )
Select R
R
15.4 k .
R
2. Inductor Selection (L1)
A. Calculate the inductor Volt • microsecond constant (E • T),
2
2
V
V
I
F = Switching Frequency (Fixed at a nominal 260 kHz).
LOAD
= 1 k
= 15.4 k .
OUT
IN
(max) = 28V
EXAMPLE (Adjustable Output Voltage Version)
(max) = 500 mA
= 20V
1
to be 1 k , 1%. Solve for R
(16.53 − 1) = 15.53 k , closest 1% value is
Application Voltage
Application Voltage
Recommended
Recommended
10
12
15
12
18
24
29
+85˚C Rating
+85˚C Rating
2
.
Voltage
Voltage
Rating
Rating
20
25
35
20
25
35
50
(Continued)
1
and R
2
, as