Datasheet

rise
2 3
3.9 R2 C1
t sec
VIN
´ ´
=
final initial
inrush load load
VOUT VOUT
I C C
Vout Slew Rate
dv
dt
-
= ´ = ´
Q1
R1
VGS VIN V
R1 R2
= - ´
+
VIN
VOUT
R1/C1
ON/OFF
Q1
Q2
R1
C1
ESD
ESD
ESD
ESD
R2
CL
(2, 3)
R2
(1)
(5)
(6)
(4)
GPIO/
Logic
Up to
8V
Supply
LOAD
TPS27081A
www.ti.com SLVSBE9D –APRIL 2012–REVISED APRIL 2013
APPLICATION INFORMATION
The TPS27081A IC is a high side load switch that integrates a Power PFET and a Control NMOS in a tiny
package. The TPS27081A internal components are rated for up to 8V supply and support up to 3A of load
current. The TPS27081A can be used in a variety applications. Figure 3 below shows a general application of
TPS27081A to control the load inrush current.
Figure 3. Typical Application Diagram
Configuring Q1 ON Resistance
The V
GS-Q1
Gate-Source voltage across the PMOS transistor Q1 sets its ON resistance R
Q1(ON)
. Directly
connecting the pin R2 to ground maximizes the ON state V
GS-Q1
and thus minimizes the VIN to VOUT voltage
dropout. When a resistor R2 is installed to control the Turn-ON slew rate then V
GS-Q1
is given by:
e.g. R1 = 10 x R2, VIN = 5V sets V
GS-Q1
= –4.5V (1)
Note: It is recommended to keep R1 > 10 x R2. Higher value of resistor R1 minimizes quiescient current when is
PMOS is on, however may adversely impact off state leakage current. Refer to the ILoad parameter in the
ELECTRICAL CHARACTERISTICS.
Configuring Turn-ON Slew Rate
Switching a large capacitive load CL instantaneously results in a load inrush current given by the following
equation:
(2)
An uncontrolled fast rising ON/OFF logic input may result in a high slew rate at the output resulting in a very high
dv/dt thus leading to a higher inrush current. To control the inrush current connect a resistor R2 and a capacitor
C1 as shown in the Electrical Characteristics Table. Use the following equation to configure the TPS27081A slew
rate to a specific value. Refer to Table 1 for component values to configure TPS27081A to achieve standard slew
rates.
(3)
Where t
rise
is the time delta starting from the ON/OFF signal’s rising edge to charge up the load capacitor CL
from 10% to 90% of VIN voltage.
Note: The t
rise
equation is accurate to within +/-20% across full VIN range supported by TPS27081A. Ensure that
R1 > 10 x R2.
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