Datasheet

SS/TR
STSELAGND
C
SS
(Optional)
LMZ31710
www.ti.com SNVS987A –JULY 2013–REVISED JULY 2013
Slow Start (SS/TR)
Connecting the STSEL pin to AGND and leaving SS/TR pin open enables the internal SS capacitor with a slow
start interval of approximately 1.2 ms. Adding additional capacitance between the SS pin and AGND increases
the slow start time. Increasing the slow start time will reduce inrush current seen by the input source and reduce
the current seen by the device when charging the output capacitors. To avoid the activation of current limit and
ensure proper start-up, the SS capacitor may need to be increased when operating near the maximum output
capacitance limit.
Table 8 shows an additional SS capacitor connected to the SS/TR pin and the STSEL pin connected to AGND.
See Table 8 below for SS capacitor values and timing interval.
Figure 33. Slow-Start Capacitor (C
SS
) and STSEL Connection
Table 8. Slow-Start Capacitor Values and Slow-Start Time
C
SS
(nF) open 3.3 4.7 10 15 22 33
SS Time (msec) 1.2 2.1 2.5 3.8 5.1 7.0 9.8
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