Datasheet

dv
1 V/μs
dt
=
dv
1.0 A 1.0 μF
dt
= ´
dv
dt
dv
Inrush Current C
dt
= ´
TPS22910A , TPS22912C , TPS22913B , TPS22913C
SLVSB49D –NOVEMBER 2011 –REVISED MAY 2014 www.ti.com
Typical Application (continued)
11.2.1 Design Requirements
Design Parameter Example Value
VIN 1.5 V to 5 V
CL 0.1 µF to 1 µF
Maximum Acceptable Inrush Current 1 A
11.2.2 Detailed Design Procedure
11.2.2.1 Inrush Current
When the switch is enabled, the output capacitors must be charged up from 0-V to VIN voltage. This charge
arrives in the form of inrush current. Inrush current can be calculated using the following equation:
(2)
Where,
C = Output capacitance
= Output slew rate
The TPS22910A, TPS22912C, and TPS22913B/C offer several different rise time options to control the inrush
current during turn-on. The appropriate device can be selected based upon the maximum acceptable slew rate
which can be calculated using the design requirements and the inrush current equation. An output capacitance of
1.0 µF will be used since the inrush follows the following equations:
(3)
(4)
To ensure an inrush current of less than 1 A, a device with a slew rate less than 1 V/µs must be used
The TPS22910A has a typical rise time of 1 µs at 3.3 V . This results in a slew rate of 3.3 V/µs which is above
the 1 V/µs requirement meaning the TPS22910 could not be used to meet the design requirements.
The TPS22913B has a typical rise time of 66 µs at 3.3 V. This results in a slew rate of 50 mV/µs which is below
the 1 V/µs requirement; therefor, the TPS22913B could be used to meet the design requirements. The
TPS22912C or TPS22913C have lower slew rates than the TPS22913B, so they could also be used, but the
output would rise more slowly.
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