LM2675M-12 National Semiconductor, LM2675M-12 Datasheet - Page 15

• 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

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 for
use 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.)
LM2675 Series Buck Regulator Design Procedure (Fixed Output)
AVX TPS
Sprague 594D
LM2675 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
= 1.21V
1
between 240
FIGURE 15. Recommended Application Voltage for AVX TPS and
Sprague 594D Tantalum Chip Capacitors Derated for 85˚C.
and 1.5 k . The lower
Application Voltage
Application Voltage
1
Recommended
Recommended
and R
3.3
2.5
3.3
10
12
15
12
18
24
29
2
5
5
8
, as
+85˚C Rating
+85˚C Rating
15
Given:
1. Programming Output Voltage (Selecting R
shown in Figure 3 )
Select R
R
R
2
2
V
V
I
F = Switching Frequency (Fixed at a nominal 260 kHz).
LOAD
= 1k (16.53 − 1) = 15.53 k , closest 1% value is 15.4 k .
= 15.4 k .
OUT
IN
(max) = 28V
EXAMPLE (Adjustable Output Voltage Version)
(max) = 1A
Voltage
Voltage
= 20V
Rating
Rating
1
to be 1 k , 1%. Solve for R
6.3
6.3
10
20
25
35
10
16
20
25
35
50
4
2
.
(Continued)
1
and R
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2
, as