lm2595sx-adj National Semiconductor Corporation, lm2595sx-adj Datasheet - Page 11

• Manufacturer Part Number: lm2595sx-adj
• Description: Simple Switcher Power Converter 150 Khz 1a Step-down Voltage Regulator
• Manufacturer: National Semiconductor Corporation

LM2595 Series Buck Regulator Design Procedure (Fixed Output)
LM2595 Series Buck Regulator Design Procedure (Adjustable Output)
Given:
V
V
I
F = Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R
shown in Figure 1 )
Use the following formula to select the appropriate resistor
values.
Select a value for R
resistor values minimize noise pickup in the sensitive feed-
back pin. (For the lowest temperature coefficient and the best
stability with time, use 1% metal film resistors.)
Procedure continued on next page.
LOAD
OUT
IN
Voltage
Output
PROCEDURE (Adjustable Output Voltage Version)
(max) = Maximum Input Voltage
(V)
3.3
12
(max) = Maximum Load Current
5
= Regulated Output Voltage
Conditions
Current
Load
(A)
0.5
0.5
0.5
1
1
1
1
between 240
FIGURE 2. LM2595 Fixed Voltage Quick Design Component Selection Table
Max Input
Voltage
(V)
10
40
10
40
10
15
40
20
40
15
18
30
40
15
20
40
5
7
6
8
9
and 1.5 k . The lower
Inductance
(µH)
100
100
150
150
150
220
150
330
22
33
47
68
47
68
33
47
68
68
47
68
68
Inductor
1
and R
Inductor
2
L24
L23
L31
L30
L13
L21
L20
L28
L31
L30
L29
L21
L19
L19
L31
L30
L36
L35
L21
L19
L26
, as
( # )
11
Through Hole Electrolytic
HFQ Series
Panasonic
Given:
V
V
I
F = Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R
shown in Figure 1 )
Select R
R
R
Example continued on next page.
LOAD
OUT
IN
330/16
270/25
220/25
180/35
220/25
150/35
150/35
330/16
220/25
180/35
180/35
180/16
120/25
100/25
220/25
180/35
180/25
2
2
(µF/V)
82/25
82/25
82/25
56/25
(max) = 28V
= 1k (16.26 − 1) = 15.26k, closest 1% value is 15.4 k .
= 15.4 k .
EXAMPLE (Adjustable Output Voltage Version)
(max) = 1A
= 20V
1
to be 1 k , 1%. Solve for R
PL Series
Nichicon
1200/25
330/16
270/25
220/35
220/35
220/16
150/25
330/16
220/25
180/35
120/35
180/16
100/25
220/25
120/25
180/25
(µF/V)
82/35
82/25
82/25
82/25
56/25
Output Capacitor
Surface Mount Tantalum
AVX TPS
220/10
220/10
220/10
220/10
220/10
100/16
100/16
220/10
220/10
220/10
100/16
220/10
100/16
Series
(µF/V)
68/20
68/20
68/20
68/20
68/20
68/20
68/20
68/20
2
.
(Continued)
595D Series
Sprague
1
330/10
270/10
220/10
180/10
220/10
150/16
100/20
270/10
220/10
150/16
120/16
150/16
100/20
120/20
120/20
100/20
120/20
100/20
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(µF/V)
68/25
68/25
68/25
and R
2
, as