LM2596 Просмотр технического описания (PDF) - First Components International
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LM2596
First Components International
LM2596 Datasheet PDF : 14 Pages
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LM2596 Simple switcher Power Converter 150kHz
3A Step-Down Voltage Regulator
PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
and must be located close to the LM2596 using short
leads and short printed circuit traces. B ecause of their fast
switching speed and low forward voltage drop, Schottky
diodes provide the best performance and efficiency, and
should be the first choice, especially in low output voltage
applications.
Ultra-fast recovery, or High-Efficiency rectifiers also
provide good results. Ultra-fast recovery diodes typically
have reverse recovery times of 50 ns or less. Rectifiers
such as the 1N5400 series are much too slow and should
not be used.
4. Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is
4. Input Capacitor (CIN)
The important parameters for the Input capacitor are the input
needed between the input pin and ground pin to prevent voltage rating and the RMS current rating. With a nominal
large volt-age transients from appearing at the input. This input voltage of 12V, an aluminum electrolytic capacitor with a
capacitor should be located close to the IC using short
leads. In addition, the RMS current rating of the input
voltage rating greater than 18V (1.5 x VIN ) would be needed. The
next higher capacitor voltage rating is 25V.
capacitor should be selected to be at least 1/2 the DC The RMS current rating requirement for the input capacitor in
load current. The capacitor manufacturers data sheet must a buck regulator is approximately 1 /2 the DC load current. In this
be checked to assure that this current rating is not
example, with a 3A load, a capacitor with a RMS current rating of
exceeded. The curve shown in Figure 9 shows typical RMS at least 1.5A is needed. The curves shown in Figure 9 can be
current ratings for several different aluminum electrolytic used to select an appropriate input capacitor.
capacitor values.
From the curves, locate the 35V line and note which capacitor
For an aluminum electrolytic, the capacitor voltage rating values have RMS current ratings greater than 1.5A. A 680UF/35V
should be approximately 1.5 times the maximum input capacitor could be used.
voltage.
For a through hole design, a 680UF/35V electrolytic capacitor
The tantalum capacitor voltage rating should be 2 times (Panasonic HFQ series or Nichicon PL series or equivalent) would
the maximum input voltage and it is recommended that be adequate. other types or other manufacturers capacitors can
they be surge current tested by the manufacturer.
be used provided the RMS ripple current ratings are adequate.
Use caution when using ceramic capacitors for input
For surface mount designs, solid tantalum capacitors can be
bypassing, because it may cause severe ringing at the VIN used, but caution must be exercised with regard to the capacitor
pin.
surge current rating. The TPS series available from AVX, and the
593D series from Sprague are both surge current tested.
LM2596 SERIES BUCK REGULATOR DESIGN PROCEDURE (FIXED OUTPUT) (Continued)
Conditions
Inductor
Output Capacitor
Through Hole Electrolytic Surface Mount Tantalum
Output
Voltage
(V)
Load
Current
(A)
Max Input
Voltage (V)
Inductance
(µH)
Inductor
(#)
Panasonic
HFQ Series
(µF/V)
Nichicon PL
Series (µF/V)
AVX TPS
Series
(µF/V)
Sprague 595D
Series (µF/V)
3.3
3
5
22
L41
470/25
560/16
330/6.3
390/6.3
7
22
L41
560/35
560/35
330/6.3
390/6.3
10
22
L41
680/35
680/35
330/6.3
390/6.3
40
33
L40
560/35
470/35
330/6.3
390/6.3
2
6
22
L33
470/25
470/35
330/6.3
390/6.3
10
33
L32
330/35
330/35
330/6.3
390/6.3
40
47
L39
330/35
270/50
220/10
330/10
5
3
8
22
L41
470/25
560/16
220/10
330/10
10
22
L41
560/25
560/25
220/10
330/10
15
33
L40
330/35
330/35
220/10
330/10
40
47
L39
330/35
270/35
220/10
330/10
2
9
22
L33
470/25
560/16
220/10
330/10
20
68
L38
180/35
180/35
100/10
270/10
40
68
L38
180/35
180/35
100/10
270/10
12
3
15
22
L41
470/25
470/25
100/16
180/16
18
33
L40
330/25
330/25
100/16
180/16
30
68
L44
180/25
180/25
100/16
120/20
40
68
L44
180/35
180/35
100/16
120/20
2
15
33
L32
330/25
330/25
100/16
180/16
20
68
L38
180/25
180/25
100/16
120/20
40
150
L42
82/25
82/25
68/20
68/25
Figure 2. LM2596 Fixed Voltage Quick Design Component Selection Table
LM2596 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
VOUT = 20V
VIN(max) = 28V
9
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