Datasheet

LM2599
SNVS123C –APRIL 1998–REVISED APRIL 2013 www.ti.com
This reduction in start up current is useful in situations where the input power source is limited in the amount of
current it can deliver. In some applications Soft-start can be used to replace undervoltage lockout or delayed
startup functions.
If a very slow output voltage ramp is desired, the Soft-start capacitor can be made much larger. Many seconds or
even minutes are possible.
If only the shutdown feature is needed, the Soft-start capacitor can be eliminated.
Figure 42. Typical Circuit Using Shutdown /Soft-start and Error Flag Features
Figure 43. Inverting −5V Regulator With Shutdown and Soft-start
lNVERTING REGULATOR
The circuit in Figure 43 converts a positive input voltage to a negative output voltage with a common ground. The
circuit operates by bootstrapping the regulator's ground pin to the negative output voltage, then grounding the
feedback pin, the regulator senses the inverted output voltage and regulates it.
This example uses the LM2599-5 to generate a −5V output, but other output voltages are possible by selecting
other output voltage versions, including the adjustable version. Since this regulator topology can produce an
output voltage that is either greater than or less than the input voltage, the maximum output current greatly
depends on both the input and output voltage. The curve shown in Figure 45 provides a guide as to the amount
of output load current possible for the different input and output voltage conditions.
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