Datasheet

RC
ON(VIN)
0.077V
I
R
=
TPS22929
SLVSB39 –DECEMBER 2011 www.ti.com
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 1.2-V, 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. During under-voltage lockout (UVLO), if the voltage level at V
OUT
exceeds the voltage level at V
IN
by
the Reverse Current Voltage Threshold (V
RVP
), the body diode will be disengaged to prevent any current flow to
V
IN
. 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.
Reverse Current Protection
In a scenario where V
OUT
is greater than V
IN
, there is potential for reverse current through the pass FET or the
body diode. The TPS22929 monitors V
IN
and V
OUT
voltage levels. When the reverse current voltage threshold
(V
RVP
) is exceeded, the switch is disabled (within 10µs typ). Additionally, the body diode is disengaged so as to
prevent any reverse current flow to V
IN
. The FET, and the output (V
OUT
), will resume normal operation when the
reverse current scenario is no longer present.
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) :TPS22929