3.3V/5V/Adjustable-Output,
Step-Up DC-DC Converters
Rectifier Diode
The ESR of both bypass and filter capacitors affects
efficiency. Best performance is obtained by using spe-
cialized low-ESR capacitors, or connecting two or more
filter capacitors in parallel. The smallest low-ESR SMT
tantalum capacitors currently available are Sprague
595D series, which are about half the size of competing
products. Sanyo OS-CON organic semiconductor
through-hole capacitors also exhibit very low ESR, and
are especially useful for operation at cold tempera-
tures. Table 1 lists suggested capacitor suppliers.
For optimum performance, a switching Schottky diode,
such as the 1N5817, is recommended. 1N5817 equiv-
alent diodes are also available in surface-mount pack-
ages from Collmer Semiconductor in Dallas, TX, phone
(214) 233-1589. The part numbers are SE014 or
SE024. For low output power applications, a pn junc-
tion switching diode, such as the 1N4148, will also
work well, although efficiency will suffer due to the
greater forward voltage drop of the pn junction diode.
MAX756/MAX757
V
IN
MINIMUM
OFF-TIME
ONE-SHOT
Q
TRIG
ONE-SHOT
LX
F/F
S
3/5
R
Q
N
V
OUT
SHDN
GND
MAXIMUM
ON-TIME
ONE-SHOT
TRIG
Q
OUT
ONE-SHOT
MAX756
LBO
N
REF
LBI
REFERENCE
Figure 2. MAX756 Block Diagram
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
