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LM3524D Datasheet - Page 12

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Typical Applications
(Continued)
A complete step-down switching regulator schematic using
the LM3524D is illustrated in Figure 15 Transistors Q1 and
Q2 have been added to boost the output to 1A The 5V
regulator of the LM3524D has been divided in half to bias
the error amplifier’s non-inverting input to within its com-
mon-mode range Since each output transistor is on for half
the period actually 45% they have been paralleled to allow
longer possible duty cycle up to 90% This makes a lower
possible input voltage The output voltage is set by
R1
V
V
1
e
a
o
NI
R2
Mounted to Staver Heatsink No V5-1
Q1
BD344
e
Q2
2N5023
e
L1
40 turns No 22 wire on Ferroxcube No K300502 Torroid core
e
l
FIGURE 15 5V 1 Amp Step-Down Switching Regulator
where V
is the voltage at the error amplifier’s non-invert-
NI
ing input
Resistor R3 sets the current limit to
200 mV
200 mV
1 3A
e
e
R3
0 15
Figure 16 and 17 show a PC board layout and stuffing dia-
gram for the 5V 1A regulator of Figure 15 The regulator’s
performance is listed in Table I
12
TL H 8650 – 20

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