LM2595
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SNVS122B –MAY 1999–REVISED APRIL 2013
Table 2. LM2595 Fixed Voltage Quick Design Component Selection Table (continued)
Conditions
Inductor
Output Capacitor
Through Hole Electrolytic Surface Mount Tantalum
Output
Voltage
(V)
Load
Current
(A)
Max Input
Inductance
Inductor
(#)
Panasonic
HFQ Series
(μF/V)
Nichicon
AVX TPS
Series
(μF/V)
220/10
220/10
220/10
100/16
220/10
100/16
68/20
Sprague
595D Series
(μF/V)
Voltage
(V)
8
(μH)
PL Series
(μF/V)
330/16
220/25
180/35
120/35
180/16
1200/25
100/25
220/25
120/25
82/25
33
47
L28
L31
L30
L29
L21
L19
L19
L31
L30
L36
L35
L21
L19
L26
330/16
220/25
180/35
180/35
180/16
120/25
100/25
220/25
180/35
82/25
270/10
220/10
150/16
120/16
150/16
100/20
68/25
10
15
40
9
1
68
5
100
68
0.5
1
20
40
15
18
30
40
15
20
40
150
150
47
68/20
120/20
120/20
100/20
68/25
68
68/20
150
220
68
68/20
12
82/25
82/25
68/20
180/25
82/25
180/25
82/25
68/20
120/20
100/20
68/25
0.5
150
330
68/20
56/25
56/25
68/20
Table 3. LM2595 Series Buck Regulator Design Procedure (Adjustable Output)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
Given:
Given:
VOUT = Regulated Output Voltage
VIN(max) = Maximum Input Voltage
ILOAD(max) = Maximum Load Current
F = Switching Frequency (Fixed at a nominal 150 kHz).
VOUT = 20V
VIN(max) = 28V
ILOAD(max) = 1A
F = Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R1 and R2, as shown in 1. Programming Output Voltage (Selecting R1 and R2, as shown in
Figure 21)
Figure 21)
Use the following formula to select the appropriate resistor values.
Select R1 to be 1 kΩ, 1%. Solve for R2.
(1)
(3)
Select a value for R1 between 240Ω and 1.5 kΩ. The lower 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.)
R2 = 1k (16.26 − 1) = 15.26k, closest 1% value is 15.4 kΩ.
R2 = 15.4 kΩ.
(2)
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