LM2576
Figure 15. Typical Test Circuit
Fixed Output Voltage Versions
Feedback
4
V
in
LM2576
L1
100
Fixed Output
µ
H
1
V
Output
2
out
3
Gnd
5
ON/OFF
7.0 V – 40 V
Unregulated
DC Input
C
in
C
out
1000
100 µF
D1
MBR360
µF
Load
C
C
D1
L1
R1
R2
–
–
–
–
–
–
100 µF, 75 V, Aluminium Electrolytic
1000 µF, 25 V, Aluminium Electrolytic
Schottky, MBR360
100 µH, Pulse Eng. PE–92108
2.0 k, 0.1%
in
out
6.12 k, 0.1%
Adjustable Output Voltage Versions
Feedback
4
V
in
LM2576
Adjustable
L1
100
V
out
µ
H
1
Output
5,000 V
2
3
Gnd
5
ON/OFF
7.0 V – 40 V
Unregulated
DC Input
R2
C
in
100
C
out
1000
µF
D1
MBR360
µF
Load
R1
R2
R1
V
V
1.0
out
ref
V
out
R2
R1
– 1.0
V
ref
Where V = 1.23 V, R1
ref
between 1.0 k and 5.0 k
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.
8
MOTOROLA ANALOG IC DEVICE DATA
MOTOROLA [ MOTOROLA ]
