Datasheet

RC
ON(VIN)
0.044V
I
R
=
TPS22913
www.ti.com SLVSB20 –SEPTEMBER 2011
APPLICATION INFORMATION
On/Off Control
The ON pin controls the state of the switch. Asserting ON high enables the switch. ON is active high and has a
low threshold, making it capable of interfacing with low-voltage signals. The ON pin is compatible with standard
GPIO logic threshold. It can be used with any microcontroller with 1.8-V, 2.5-V or 3.3-V GPIOs.
Input Capacitor
To limit the voltage drop on the input supply caused by transient inrush currents when the switch turns on into a
discharged load capacitor or short-circuit, a capacitor needs to be placed between VIN and GND. A 1-μF ceramic
capacitor, CIN, placed close to the pins is usually sufficient. Higher values of CIN can be used to further reduce
the voltage drop.
Output Capacitor
A C
IN
to C
L
ratio of 10 to 1 is recommended for minimizing V
IN
dip caused by inrush currents during startup.
Output Pull-Down
The output pulldown is active when the user is turning off the main pass FET. The pulldown discharges the
output rail to approximately 10% of the rail, and then the output pulldown is automatically disconnected to
optimize the shutdown current.
Under-Voltage Lockout
The under-voltage lockout turns-off the switch if the input voltage drops below the under-voltage lockout
threshold. With the ON pin active the input voltage rising above the under-voltage lockout threshold will cause a
controlled turn-on of the switch which limits current over-shoots. During under-voltage lockout (UVLO), no
reverse current can flow as the body diode is not engaged.
Reverse Current Protection
In a scenario where V
OUT
is greater than V
IN
, there could be reverse current through the body diode of the PMOS
FET. The TPS22913 monitors the current through the FET and shuts off the FET when a reverse current is
detected. The FET, and the output, resumes normal operation when the reverse current scenario is no longer
present. When the reverse current protection (RCP) is active, no reverse current can flow as the body diode is
not engaged. During under-voltage lockout (UVLO), or when the switch is disabled, no reverse current can flow
as the body diode is not engaged.
Use the following formula to calculate the amount of reverse current for a particular application:
Where,
I
RC
is the amount of reverse current,
R
ON(VIN)
is the on-resistance at the VIN of the reverse current condition.
Board Layout
For best performance, all traces should be as short as possible. To be most effective, the input and output
capacitors should be placed close to the device to minimize the effects that parasitic trace inductances may have
on normal operation. Using wide traces for V
IN
, V
OUT
, and GND helps minimize the parasitic electrical effects
along with minimizing the case to ambient thermal impedance.
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Product Folder Link(s) :TPS22913