AAT4280A_0511 Datasheet, PDF (9/14 Pages) Advanced Analogic Technologies – Slew Rate Controlled Load Switch

Functional Block Diagram
IN
AAT4280A
Slew Rate Controlled Load Switch
OUT
ON/OFF
Level
Shift
Turn-On
Slew Rate
Control
*
GND
*AAT4280A-3 only
Functional Description
The AAT4280A is a family of flexible P-channel
MOSFET power switches designed for high-side
load switching applications. There are three ver-
sions of the AAT4280A with different turn-on and
turn-off characteristics to choose from, depending
upon the specific requirements of an application.
The first version, the AAT4280A-1, has a moderate
turn-on slew rate feature, which reduces inrush
current when the MOSFET is turned on. This func-
tion allows the load switch to be implemented with
either a small input capacitor or no input capacitor
at all. During turn-on slewing, the current ramps
linearly until it reaches the level required for the
output load condition. The proprietary turn-on cur-
rent control method works by careful control and
monitoring of the MOSFET gate voltage. When the
device is switched ON, the gate voltage is quickly
increased to the threshold level of the MOSFET.
Once at this level, the current begins to slew as the
gate voltage is slowly increased until the MOSFET
becomes fully enhanced. Once it has reached this
point, the gate is quickly increased to the full input
voltage and R_DS(ON) is minimized.
The second version, the AAT4280A-2, is a very fast
switch intended for high-speed switching applica-
tions. This version has no turn-on slew rate control
and no special output discharge features.
The final switch version, the AAT4280A-3, has the
addition of a minimized slew rate limited turn-on
function and a shutdown output discharge circuit to
rapidly turn off a load when the load switch is dis-
abled through the ON/OFF pin.
All versions of the AAT4280A operate with input
voltages ranging from 1.5V to 5.5V. All versions of
this device have extremely low operating current,
making them ideal for battery-powered applica-
tions. The ON/OFF control pin is TTL compatible
and will also function with 2.5V to 5V logic systems,
making the AAT4280A an ideal level-shifting load
switch.
4280A.2005.11.1.3
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