LM2574-12 Motorola Inc, LM2574-12 Datasheet - Page 8

• Manufacturer Part Number: LM2574-12
• Description: EASY SWITCHERE 0.5 A STEP-DOWN VOLTAGE REGULATOR
• Manufacturer: Motorola Inc

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 16, to minimize
inductance and ground loops, the length of the leads
indicated by heavy lines should be kept as short as possible.
ground plane construction should be used.
8
As in any switching regulator, the layout of the printed
For best results, single–point grounding (as indicated) or
7.0 V – 40 V
Unregulated
DC Input
Unregulated
7.0 – 40 V
DC Input
C in
22 F
V in
1
C in
22 F
C in
C out –
D1
L1
R1
R2
4
V in
Figure 16. Test Circuit and Layout Guidelines
1
–
–
–
–
–
Pwr
Gnd
Adjustable
Adjustable Output Voltage Versions
4
LM2574
22 F, 60 V, Aluminium Electrolytic
220 F, 25 V, Aluminium Electrolytic
Schottky, 1N5819
330 H, (For 5.0 V in , 3.3 V out , use 100 H)
2.0 k, 0.1%
6.12 k, 0.1%
Fixed Output Voltage Versions
2
Pwr
Gnd
Fixed Output
PCB LAYOUT GUIDELINES
Sig
Gnd
LM2574
V out
R2
Where V ref = 1.23 V, R1
between 1.0 k and 5.0 k
2
+
3
+
Sig
Gnd
R1
V
ON/OFF
ref
LM2574
V out
V
3
7
ref
1
Output
Feedback
1.0
ON/OFF
– 1.0
)
7
Feedback
1
Output
R2
R1
(emitter of the internal switch) of the LM2574 should be kept
to a minimum in order to minimize coupling to sensitive
circuitry.
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
LM2574 regulator.
On the other hand, the PCB area connected to the Pin 7
Another sensitive part of the circuit is the feedback. It is
330 H
D1
1N5819
L1
330 H
D1
1N5819
L1
MOTOROLA ANALOG IC DEVICE DATA
C out
220 F
C out
220 F
R2
6.12 k
R1
2.0 k
Load
V out
Load
5.0 V
V out