AAT4250
Slew Rate Controlled Load Switch
Functional Block Diagram
OUT
IN
Slew Rate
Control
Under-
voltage
Lockout
Level
Shift
ON/OFF
GND
rent when the MOSFET is turned on, allowing the
AAT4250 to be implemented with a small input
capacitor, or no input capacitor at all. During slew-
ing, the current ramps linearly until it reaches the
level required for the output load condition. The
proprietary control method works by careful control
and monitoring of the MOSFET gate voltage. When
the device is switched ON, the gate voltage is quick-
ly 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 RDS(ON) is minimized.
Functional Description
The AAT4250 is a slew rate controlled P-channel
MOSFET power switch designed for high-side load-
switching applications. It operates with input volt-
ages ranging from 1.8V to 5.5V which, along with its
extremely low operating current, makes it ideal for
battery-powered applications. In cases where the
input voltage drops below 1.8V, the AAT4250 MOS-
FET is protected from entering the saturated region
of operation by automatically shutting down. In
addition, the TTL compatible ON/OFF pin makes
the AAT4250 an ideal level shifted load-switch. The
slew rate controlling feature eliminates in-rush cur-
4250.2001.12.0.94
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