MAX756/MAX757 3.3V/5V/Adjustable-Output,Step-Up DC-DC ConvertersRectifier Diode The ESR of both bypass and filter capacitors affects For optimum performance, a switching Schottky diode, efficiency. Best performance is obtained by using spe- such as the 1N5817, is recommended. 1N5817 equiv- cialized low-ESR capacitors, or connecting two or more alent diodes are also available in surface-mount pack- filter capacitors in parallel. The smallest low-ESR SMT ages from Collmer Semiconductor in Dallas, TX, phone tantalum capacitors currently available are Sprague (214) 233-1589. The part numbers are SE014 or 595D series, which are about half the size of competing SE024. For low output power applications, a pn junc- products. Sanyo OS-CON organic semiconductor tion switching diode, such as the 1N4148, will also through-hole capacitors also exhibit very low ESR, and work well, although efficiency will suffer due to the are especially useful for operation at cold tempera- greater forward voltage drop of the pn junction diode. tures. Table 1 lists suggested capacitor suppliers. VIN Q TRIG MINIMUM OFF-TIME ONE-SHOT ONE-SHOT SHDN LX VOUT F/F S Q N 3/5 R GND MAXIMUM ON-TIME TRIG Q ONE-SHOT ONE-SHOT OUT MAX756 LBO REF N REFERENCE LBI Figure 2. MAX756 Block Diagram Maxim Integrated 7
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