AAT4282A Datasheet, PDF (9/14 Pages) Advanced Analogic Technologies – Dual Slew Rate Controlled Load Switch

AAT4282A
Dual Slew Rate Controlled Load Switch
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 thresh-
old level of the MOSFET. Once at this level, the
current begins to slew as the gate voltage is slow-
ly increased until the MOSFET becomes fully
enhanced. Once it has reached this point the gate
is quickly increased to the full input voltage and
the R_DS(ON) is minimized.
The second version, the AAT4282A-2, is a very
fast switch intended for high-speed switching
applications.
This version has no turn-on slew rate control and
no special output discharge features. The final
switch version, the AAT4282A-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. Using the FAST input pin
on the AAT4282A-3, the device can be manually
switched to a slower slew rate.
All versions of the AAT4282A operate with input
voltages ranging from 1.5V to 6.5V. All versions of
this device have extremely low operating current,
making them ideal for battery-powered applications.
The ON/OFF control pin is TTL compatible and will
also function with 2.5V to 5V logic systems, making
the AAT4282A an ideal level-shifting load switch.
Applications Information
Input Capacitor
A 1μF or larger capacitor is typically recommended
for C_IN in most applications. A C_IN capacitor is not
required for basic operation; however, it is useful in
preventing load transients from affecting upstream
circuits. C_IN should be located as close to the
device VIN pin as practically possible. Ceramic,
tantalum, or aluminum electrolytic capacitors may
be selected for C_IN. There is no specific capacitor
equivalent series resistance (ESR) requirement for
C_IN. However, for higher current operation, ceram-
ic capacitors are recommended for C_IN due to their
inherent capability over tantalum capacitors to with-
stand input current surges from low-impedance
sources, such as batteries in portable devices.
Output Capacitor
For proper slew operation, a 0.1μF capacitor or
greater is required between VOUT and GND.
Likewise, with the output capacitor, there is no spe-
cific capacitor ESR requirement. If desired, C_OUT
may be increased without limit to accommodate
any load transient condition without adversely
affecting the slew rate.
Enable Function
The AAT4282A features an enable / disable func-
tion. This pin (ON) is active high and is compatible
with TTL or CMOS logic. To assure the load switch
will turn on, the ON control level must be greater
than 1.4V. The load switch will go into shutdown
mode when the voltage on the ON pin falls below
0.4V. When the load switch is in shutdown mode,
the OUT pin is tri-stated, and quiescent current
drops to leakage levels below 1μA.
Reverse Output-to-Input Voltage
Conditions and Protection
Under normal operating conditions, a parasitic
diode exists between the output and input of the
load switch. The input voltage should always
remain greater than the output load voltage, main-
taining a reverse bias on the internal parasitic
diode. Conditions where V_OUT might exceed V_IN
should be avoided since this would forward bias
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