LM2576
Fixed Output Voltage Versions
Feedback
V
in
1
4
LM2576
Fixed Output
Output
2
ON/OFF
D1
MBR360
C
out
1000
mF
Load
L1
100
mH
V
out
3
7.0 V − 40 V
Unregulated
DC Input
C
in
100
mF
GN
D
5
C
in
C
out
D1
L1
R1
R2
−
−
−
−
−
−
100
mF,
75 V, Aluminium Electrolytic
1000
mF,
25 V, Aluminium Electrolytic
Schottky, MBR360
100
mH,
Pulse Eng. PE−92108
2.0 k, 0.1%
6.12 k, 0.1%
Adjustable Output Voltage Versions
Feedback
V
in
1
4
LM2576
Adjustable
Output
2
ON/OFF
D1
MBR360
C
out
1000
mF
R2
Load
R1
L1
100
mH
V
out
5,000 V
3
7.0 V − 40 V
Unregulated
DC Input
C
in
100
mF
GN
D
5
V out
+
V
R2
+
R1
ref
1.0
)
R2
R1
– 1.0
V out
V
ref
Where V
ref
= 1.23 V, R1
between 1.0 k and 5.0 k
Figure 15. Typical Test Circuit
PCB LAYOUT GUIDELINES
As in any switching regulator, the layout of the printed
circuit board is very important. Rapidly switching currents
associated with wiring inductance, stray capacitance and
parasitic inductance of the printed circuit board traces can
generate voltage transients which can generate
electromagnetic interferences (EMI) and affect the desired
operation. As indicated in the Figure 15, to minimize
inductance and ground loops, the length of the leads
indicated by heavy lines should be kept as short as possible.
For best results, single−point grounding (as indicated) or
ground plane construction should be used.
On the other hand, the PCB area connected to the Pin 2
(emitter of the internal switch) of the LM2576 should be
kept to a minimum in order to minimize coupling to sensitive
circuitry.
Another sensitive part of the circuit is the feedback. It is
important to keep the sensitive feedback wiring short. To
assure this, physically locate the programming resistors near
to the regulator, when using the adjustable version of the
LM2576 regulator.
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