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