Datasheet

EN
TPS54040A
3
SS/TR
4
PWRGD
6
EN
TPS54040A
3
SS/TR4
PWRGD6
EN1,EN2
VOUT1
VOUT2
EN1
PWRGD1
VOUT1
VOUT2
SS /TR
TPS54040A
EN
PWRGD
SS /TR
EN
PWRGD
TPS54040A
SLVSB58A MARCH 2012REVISED JANUARY 2014
www.ti.com
DETAILED DESCRIPTION (continued)
Figure 32. Schematic for Sequential Start-Up Figure 33. Sequential Startup using EN and
Sequence PWRGD
Figure 34. Schematic for Ratiometric Start-Up Figure 35. Ratio-Metric Startup using Coupled
Sequence SS/TR pins
Figure 34 shows a method for ratio-metric start up sequence by connecting the SS/TR pins together. The
regulator outputs will ramp up and reach regulation at the same time. When calculating the slow start time the
pull up current source must be doubled in Equation 6. Figure 35 shows the results of Figure 34.
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