LM3524 National Semiconductor, LM3524 Datasheet - Page 12

• Manufacturer Part Number: LM3524
• Description: Regulating Pulse Width Modulator
• Manufacturer: National Semiconductor

www.national.com
Typical Applications
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 regu-
lator of the LM3524D has been divided in half to bias the er-
ror amplifier’s non-inverting input to within its common-mode
*Mounted to Staver Heatsink No. V5-1.
Q1 = BD344
Q2 = 2N5023
L1 =
FIGURE 14. Inductor Current Slope in Step-Down
>
40 turns No. 22 wire on Ferroxcube No. K300502 Torroid core.
Regulator
FIGURE 15. 5V, 1 Amp Step-Down Switching Regulator
(Continued)
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12
range. Since each output transistor is on for half the period,
actually 45%, they have been paralleled to allow longer pos-
sible duty cycle, up to 90%. This makes a lower possible in-
put voltage. The output voltage is set by:
where V
input.
Resistor R3 sets the current limit to:
Figures 16, 17 and 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 1 .
NI
is the voltage at the error amplifier’s non-inverting
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