LM1577, LM2577
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SNOS658D –JUNE 1999–REVISED APRIL 2013
Table 3. Aluminum Electrolytic Capacitors
Recommended for Switching Regulators
Cornell Dublier —Types 239, 250, 251, UFT, 300, or 350
P.O. Box 128, Pickens, SC 29671
(803) 878-6311
Nichicon —Types PF, PX, or PZ
927 East Parkway,
Schaumburg, IL 60173
(708) 843-7500
Sprague —Types 672D, 673D, or 674D
Box 1, Sprague Road,
Lansing, NC 28643
(919) 384-2551
United Chemi-Con —Types LX, SXF, or SXJ
9801 West Higgins Road,
Rosemont, IL 60018
(708) 696-2000
If the LM1577 is located far from the supply source filter capacitors, an additional large electrolytic capacitor (e.g.
47 μF) is often required.
5. Diode Selection (D)
The switching diode used in the boost regulator must withstand a reverse voltage equal to the circuit output
voltage, and must conduct the peak output current of the LM2577. A suitable diode must have a minimum
reverse breakdown voltage greater than the circuit output voltage, and should be rated for average and peak
current greater than ILOAD(max) and ID(PK). Schottky barrier diodes are often favored for use in switching regulators.
Their low forward voltage drop allows higher regulator efficiency than if a (less expensive) fast recovery diode
was used. See Table 4 for recommended part numbers and voltage ratings of 1A and 3A diodes.
Table 4. Diode Selection Chart
VOUT
(max)
20V
Schottky
Fast Recovery
1A
3A
1A
3A
1N5817
MBR120P
1N5818
MBR130P
11DQ03
1N5819
MBR140P
11DQ04
MBR150
11DQ05
1N5820
MBR320P
1N5821
MBR330P
31DQ03
1N5822
MBR340P
31DQ04
MBR350
31DQ05
30V
40V
1N4933
MUR105
1N4934
HER102
MUR110
10DL1
50V
MR851
30DL1
100V
MR831
HER302
BOOST REGULATOR CIRCUIT EXAMPLE
By adding a few external components (as shown in Figure 37), the LM2577 can be used to produce a regulated
output voltage that is greater than the applied input voltage. Typical performance of this regulator is shown in
Figure 38 and Figure 39. The switching waveforms observed during the operation of this circuit are shown in
Figure 40.
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