Datasheet

LM1577, LM2577
www.ti.com 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
[phone]
Nichicon —Types PF, PX, or PZ
927 East Parkway,
Schaumburg, IL 60173
[phone]
Sprague —Types 672D, 673D, or 674D
Box 1, Sprague Road,
Lansing, NC 28643
[phone]
United Chemi-Con —Types LX, SXF, or SXJ
9801 West Higgins Road,
Rosemont, IL 60018
[phone]
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 I
LOAD(max)
and I
D(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
V
OUT
Schottky Fast Recovery
(max) 1A 3A 1A 3A
20V 1N5817 1N5820
MBR120P MBR320P
1N5818 1N5821
30V MBR130P MBR330P
11DQ03 31DQ03
1N5819 1N5822
40V MBR140P MBR340P
11DQ04 31DQ04
MBR150 MBR350 1N4933
50V 11DQ05 31DQ05 MUR105
1N4934 MR851
100V HER102 30DL1
MUR110 MR831
10DL1 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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