AAT4280A datasheet(9/14 Pages) ANALOGICTECH

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AAT4280A

Slew Rate Controlled Load Switch

4280A.2005.02.1.1

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, AAT4280A-1, has a moderate

turn-on slew rate feature, which reduces in-rush

current when the MOSFET is turned on. This func-

tion allows the load switch to be implemented with

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 current 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 applications.

This version

has no turn-on slew rate control and no special out-

put 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 disabled 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.

Functional Block Diagram

Level

Shift

ON/OFF

OUT

GND

Turn-On

Slew Rate

Control

*AAT4280A-3 only

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