LM2575
Figure 14. Typical Test Circuit
5.0 Output Voltage Versions
Feedback
Vin
+
1
4
LM2575–5
Output
3
Cin
100
µF/50
V
Gnd
5
2
ON/OFF
D1
1N5819
Cout
330
µF
/16 V
Load
L1
330
µH
Vout
Regulated
Output
Vin
Unregulated
DC Input
8.0 V – 40 V
–
Adjustable Output Voltage Versions
Feedback
Vin
+
1
4
LM2575
Adjustable
Output
2
ON/OFF
D1
1N5819
Cout
330
µF
/16 V
R2
Load
R1
L1
330
µH
Vout
Regulated
Output
3
Unregulated
DC Input
8.0 V – 40 V
Cin
100
µF/50
V
Gnd
5
–
V out
+
Vref 1
)
R2
R1
V out
V
ref
–1
R2
+
R1
Where Vref = 1.23 V, R1
between 1.0 kΩ and 5.0 kΩ
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 14, 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 LM2575 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
LM2575 regulator.
MOTOROLA ANALOG IC DEVICE DATA
7
MOTOROLA [ MOTOROLA, INC ]
