IL2595-xx
Input power sources that are current limited or sources that can not deliver these currents without getting loaded down,
may not work correctly. Because of the relatively high startup currents required by the inverting topology, the delayed
startup feature (C1, R1 and R2) shown in Figure 6 is recommended. By delaying the regulator startup, the input capacitor
is allowed to charge up to a higher voltage before the switcher begins operating. A portion of the high input current
needed for startup is now supplied by the input capacitor (C
IN
). For severe start up conditions, the input capacitor can be
made much larger than normal.
INVERTING REGULATOR SHUTDOWN METHODS
To use the ON /OFF pin in a standard buck configuration is simple, pull it below 1.3V (@25°C, referenced to ground) to
turn regulator ON, pull it above 1.3V to shut the regulator OFF. With the inverting configuration, some level shifting is
required, because the ground pin of the regulator is no longer at ground, but is now setting at the negative output voltage
level. Two different shutdown methods for inverting regulators are shown in Figure 8 and Figure 9.
FIGURE 8. Inverting Regulator Ground Referenced Shutdown
FIGURE 9. Inverting Regulator Ground Referenced Shutdown using Opto Device
Rev. 00 9
IKSEMICON [ IK SEMICON CO., LTD ]
