LM3578AN National Semiconductor, LM3578AN Datasheet - Page 15

• Manufacturer Part Number: LM3578AN
• Description: DC/DC Converter IC
• Manufacturer: National Semiconductor

Specifications of LM3578AN

• Input Voltage: 40V
• Output Voltage: 1V
• No. Of Pins: 8
• Mounting Type: Through Hole
• Output Voltage Min: -1V
• Voltage Regulator Type: Switching
• Output Current Max: 750mA
• Peak Reflow Compatible (260 C): No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Typical Applications
BOOST REGULATOR
The boost regulator converts a low input voltage into a
higher output voltage. The basic configuration is shown in
Figure 18. Energy is stored in the inductor while the transis-
tor is on and then transferred with the input voltage to the
output capacitor for filtering when the transistor is off. Thus,
The circuit of Figure 19 converts a 5V supply into a 15V
supply with 150 mA of output current, a load regulation of
14 mV (30 mA to 140 mA), and a line regulation of 35 mV
(4.5V ≤ V
V
V
V
I
o
in
o
ripple
= 1.5A
in
= 5V
= 15V
FIGURE 18. Basic Boost Regulator
≤ 8.5V).
= 50 mV
V
o
= V
in
+ V
R4 = 200Ω
R5 = 330Ω
C1 = 1820 pF
C2 = 330 µF
in
FIGURE 17. Buck Converter with Boosted Output Current
(t
on
/t
(Continued)
off
).
00871109
15
R1 = (V
R3 = V/(I
where:
∆I
∆I
R4, C3 and C4 are necessary for continuous operation and
are typically 220 kΩ, 20 pF, and 0.0022 µF respectively.
C1 is the timing capacitor found in Figure 1.
L
L
= 2(I
is 200 mA in this example.
f
R1 = 40 kΩ
R2 = 10 kΩ
R3 = 0.05Ω
V
V
V
I
f
R1 = 140 kΩ
R2 = 10 kΩ
R3 = 0.15Ω
osc
o
osc
o
in
o
ripple
FIGURE 19. Boost or Step-Up Regulator
LOAD(min)
= 140 mA
L(max, DC)
− 1) R2 where R2 = 10 kΩ.
= 15V
= 5V
= 50 kHz
= 50 kHz
C2 ≥ I
= 10 mV
)(V
+ 0.5 ∆I
o
o
(V
/V
00871108
in
o
)
− V
L
)
in
)/(f
C3 = 20 pF
L1 = 220 µH
D1 = 1N5819
Q1 = D45
R4 = 200 kΩ
C1 = 1820 pF
C2 = 470 µF
C3 = 20 pF
C4 = 0.0022 µF
L1 = 330 µH
D1 = 1N5818
osc
V
o
V
ripple
).
00871111
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