LM2574DW-5 데이터 시트보기 (PDF) - Motorola => Freescale
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LM2574DW-5 Datasheet PDF : 24 Pages
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7.0 – 40 V
Unregulated
DC Input
LM2574
Figure 16. Test Circuit and Layout Guidelines
Fixed Output Voltage Versions
Vin
1
Cin
22 µF
Feedback
LM2574
Fixed Output
1
Output
L1
330 µH
7
4 Pwr 2 Sig 3 ON/OFF
Gnd Gnd
D1
1N5819
Vout
Cout
Load
220 µF
7.0 V – 40 V
Unregulated
DC Input
Cin –
Cout –
D1 –
L1 –
R1 –
R2 –
22 µF, 60 V, Aluminium Electrolytic
220 µF, 25 V, Aluminium Electrolytic
Schottky, 1N5819
330 µH, (For 5.0 Vin, 3.3 Vout, use 100 µH)
2.0 k, 0.1%
6.12 k, 0.1%
Adjustable Output Voltage Versions
Vin
1
Cin
22 µF
Feedback
LM2574
Adjustable
1
Output
L1
330 µH
7
4 Pwr 2 Sig 3 ON/OFF
Gnd Gnd
D1
1N5819
ǒ Ǔ + ) Vout
Vref 1.0
R2
R1
ǒ Ǔ + R2
R1
Vout
Vref
–
1.0
Where Vref = 1.23 V, R1
between 1.0 kΩ and 5.0 kΩ
Cout
220 µF
R2
6.12 k
R1
2.0 k
Vout
5.0 V
Load
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 16, 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 7
(emitter of the internal switch) of the LM2574 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
LM2574 regulator.
8
MOTOROLA ANALOG IC DEVICE DATA
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