Datasheet

SS/TR
STSELAGND
C
SS
(Optional)
LMZ35003
www.ti.com SNVS988 –JULY 2013
Slow Start (SS/TR)
For outputs voltages of 5V or less, the slow start capacitance built into the LMZ35003 is sufficient to provide for a
turn-on ramp rate that does not induce large surge currents while charging the output capacitors. Connecting the
STSEL pin (Pin 29) to AGND while leaving SS pin (Pin 28) open enables the internal SS capacitor with a slow
start interval of approximately 5 ms. For output voltages greater than 5V, additional slow start capacitance is
recommended. For 12V to 15V output voltages, a 22nF capacitor should be connected between the SS/TR pin
(Pin 28) and AGND, while connecting the STSEL pin (Pin 29) to AGND as well. Figure 35 shows an additional
SS capacitor connected to the SS pin and the STSEL pin connected to AGND. See Table 6 below for SS
capacitor values and timing interval.
Figure 35. Slow Start Capacitor (C
SS
) and STSEL Connection
Table 6. Slow Start Capacitor Values and Slow Start Time
C
SS
(nF) open 4.7 10 15 22
SS Time (msec) 5 7 10 13 17
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