A8439 Ver la hoja de datos (PDF) - Allegro MicroSystems
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A8439 Datasheet PDF : 14 Pages
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A8439
Photoflash Capacitor Charger with IGBT Driver and Refresh
Figure 7 shows the last charging cycle, when the CHARGE pin is
forced low before charging has been completed.
The A8439 implements an adaptive off-time, tOFF , control.
After the switch is turned off, a sensing circuit tracks the flyback
voltage at the SW node. As soon as this voltage swings below
1.2 V, the switch is turned on again for the next charging cycle.
However, when the photoflash capacitor charger circuit starts
up at low output voltage, a timeout may be triggered to limit the
maximum switch off-time to 20 μs.
Figure 7. Last charging cycle, when the CHARGE pin is forced low before
charging is complete.
Allegro MicroSystems, Inc.
11
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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