Datasheet

RES
SS
HG
Current Limit Detected
at CS
Current Limit Persistent
Charge Restart cap
with 50 PA current
Discharge Restart
cap with 1.2 PA
11PA
0.2V
FB+120 mV
t2
t1
1.2V
0V
RES
Hiccup
current
source
logic
Current
limit cycle
limit cycle
CLK
+
-
LM25088
R
S
Q
+
-
HG OFF
SS begins
Restart
Q
SS = 0
50 PA
5.0V
Non- current
C
RES
Post-fault
Discharge
current
I-Limit
0.2V
1.2V
1.2 PA
27 PA
LM25088
LM25088-Q1
www.ti.com SNVS609H –DECEMBER 2008–REVISED MARCH 2013
Figure 21. Current Limit Restart Circuit
Figure 22. Current Limit Restart Timing Diagram
Soft-Start
The soft-start (SS) feature forces the output to rise linearly until it reaches the steady-state operating voltage set
by the feedback resistors. The LM25088 will regulate the FB pin to the SS pin voltage or the internal 1.205V
reference, which ever is lower. At the beginning of the soft-start sequence VSS = 0V and, an internal 11 µA
current source gradually increases the voltage of the external soft-start capacitor (C
SS
). An internal amplifier
clamps the SS pin voltage at 120 mV above the FB voltage. This feature provides soft-start controlled recovery
with reduced output overshoot in the event that the output voltage momentarily dips out of regulation.
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