LM2672MX-12 NSC [National Semiconductor], LM2672MX-12 Datasheet - Page 17

• Manufacturer Part Number: LM2672MX-12
• Manufacturer: NSC [National Semiconductor]

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 6.0 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.
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.)
LM2672 Series Buck Regulator
Design Procedure (Adjustable
Output)
V
V
I
F = Switching Frequency (Fixed at a nominal 260 kHz).
LOAD
OUT
IN
(max) = Maximum Input Voltage
PROCEDURE (Adjustable Output Voltage Version)
(max) = Maximum Load Current
= Regulated Output Voltage
1
between 240
where V
FIGURE 15. Recommended Application Voltage for AVX TPS and
REF
Sprague 594D Tantalum Chip Capacitors Derated for 85˚C.
= 1.21V
and 1.5 k . The lower
Recommended
Application Voltage
Recommended
Application Voltage
1
and R
2
3.3
2.5
3.3
10
12
15
12
18
24
29
, as
5
5
8
Sprague 594D
+85˚C Rating
+85˚C Rating
AVX TPS
17
Given:
1. Programming Output Voltage (Selecting R
Select R
R
R
shown in Figure 3 )
2
2
V
V
I
F = Switching Frequency (Fixed at a nominal 260 kHz).
LOAD
= 1 k
= 15.4 k .
OUT
IN
Voltage
Rating
Voltage
Rating
(max) = 28V
EXAMPLE (Adjustable Output Voltage Version)
(max) = 1A
= 20V
1
to be 1 k , 1%. Solve for R
6.3
6.3
(16.53 − 1) = 15.53 k , closest 1% value is 15.4 k .
10
20
25
35
10
16
20
25
35
50
4
2
.
1
and R
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2
, as