SmartSwitch
TM
General Description
The AAT4280 SmartSwitchTM is a member of AATI's
Application Specific Power MOSFETTM (ASPMTM)
product family. The AAT4280 is a P-channel MOS-
FET power switch designed for high-side load-
switching applications. The P-channel MOSFET
device has a typical R
DS(ON)
of 80m
, allowing
increased load switch power handling capacity. This
device is available in three different versions with
flexible turn on and off characteristics from very fast
to slew rate limited. The standard AAT4280 (-1) ver-
sion has a slew rate limited turn on load switch and
is functionally compatible with the AAT42
50 device
while offering superior R
DS(ON)
characteristics. The
AAT4280 (-2) version features fast load switch turn
on capabilities, typically less than 210ns turn on and
3s turn off times. The AAT4280 (-3) variation offers
a shutdown load discharge circuit to rapidly turn off
a load circuit when the switch is disabled. All
AAT4280 load switch versions operate with an input
voltage ranging from 1.8V to 5.5V, making them
ideal for both 3V and 5V systems. The AAT4280
also features an under voltage lock out which turns
the switch off when an input under-voltage condition
exists. Input logic levels are TTL and 2.5 volt to 5
volt CMOS compatible. The quiescent supply cur-
rent is very low, typically 2
.5A. In shutdown mode,
the supply current decreases to less than 1A.
The AAT4280 is available in a 6 pin SOT23 or 8
pin SC70JW package and is specified over -40C
to 85C temperature range.
Features
1.8V to 5.5V Input voltage range
Very Low R
DS(ON)
, typically 80m
(5V)
Slew rate limited turn-on time options
1ms
0.
5s
100s
Fast shutdown load discharge option
Low quiescent current
2.5A typ
1A max in shutdown
TTL/CMOS input logic level
Temperature range -40C to 85C
4kV ESD rating
6 pin SOT23 or SC70JW-8 package
Applications
Cellular telephones
Digital still cameras
Personal digital assistants (PDA)
Hot swap supplies
Notebook computers
Personal communication devices
AAT4280
Slew Rate Controlled Load Switch
Typical Application
AAT4280
C
OUT
0.1
F
C
IN
1
F
OUT
IN
GND
V
OUT
GND
GND
V
IN
ON/OFF
GND
IN
ON
Preliminary
Information
4280.2002.2.0.92
1
Pin Descriptions
Pin Configuration
SOT23-6
(Top View)
SC70JW-8
(Top View)
Selector Guide
Slew Rate
Active
Part Number
(typ)
Pull Down
Enable
AAT4280-1
1mS
Active High
AAT4280-2
0.5
S
Active High
AAT4280-3
100S
Active High
OUT
ON/OFF
GND
1
2
IN
IN
IN
IN
IN
1
2
3
4
8
7
6
5
1
2
3
OUT
ON/OFF
GND
4
5
6
IN
GND
IN
Pin #
SOT23-6
SC70JW
Symbol
Function
1
2
OUT
The pin is the P-channel MOSFET drain connection.
Bypass to ground through a 0.1uF capacitor.
2,5
4
GND
Ground connection
3
3
ON/OFF
Enable Input
4,6
1,5,6,7,8
IN
The pin is the input to the P-channel MOSFET source.
Bypass to ground through a 1.0uF capacitor.
AAT4280
Slew Rate Controlled Load Switch
2
4280.2002.2.0.92
Absolute Maximum Ratings
(T
A
=25C unless otherwise noted)
Note: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at con-
ditions other than the operating conditions specified is not implied. Only one Absolute Maximum rating should be applied at any one time.
Note 1: Human body model is a 100pF capacitor discharged through a 1.5k
resistor into each pin.
Thermal Characteristics
Note 2: Mounted on an AAT4280 demo board in still 25C air.
Value
Symbol
Description
SOT23-6
SC70JW-8
Units
JA
Thermal Resistance (SOT23-
6 or SC70JW-8)
2
120
140
C/W
P
D
Power Dissipation (SOT23-
6 or SC70JW-8)
2
833
714
mW
Symbol
Description
Value
Units
V
IN
IN to GND
-0.3 to 6
V
V
ON
ON/OFF to GND
-0.3 to 6
V
V
OUT
OUT to GND
-0.3 to V
IN
+0.3
V
I
MAX
Maximum Continuous Switch Current
2.3
A
I
DM
Maximum Pulsed Current
IN
2.5V
6
A
IN < 2.5V
3
A
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at Leads)
300
C
V
ESD
ESD Rating
1
- HBM
4000
V
AAT4280
Slew Rate Controlled Load Switch
4280.2002.2.0.92
3
Electrical Characteristics
(V
IN
= 5V, T
A
= -40 to 85C unless otherwise noted. Typical values
are at T
A
=25C)
Note 3: Part requires minimum start-up of V
IN
2.0V to ensure operation down to 1.8V
Note 4: For V
IN
outside this range consult typical ON/OFF threshold curve.
Symbol
Description
Conditions
Min
Typ
Max
Units
AAT4280 All Versions
V
IN
Operation Voltage
1.8
3
5.5
V
V
UVLO
Undervoltage Lockout
V
IN
falling
1.0
1.4
1.8
V
V
UVLO(hys)
Undervoltage Lockout Hysteresis
250
mV
I
Q
Quiescent Current
ON/OFF= active
2.5
4
uA
I
Q
(off)
Off supply current
ON/OFF= inactive, OUT=open
1
uA
I
SD
(off)
Off switch current
ON/OFF= inactive, V
OUT
=0
1
uA
R
DS(on)
On -resistance
V
IN
=5V, T
A
=25 C
80
120
m
V
IN
=4.2V, T
A
=25 C
85
130
V
IN
=3V, T
A
=25 C
100
150
V
IN
=1.8V, T
A
=25 C
160
250
TC
RDS
On-Resistance Temp -Co
2800
ppm/C
V
IL
ON/OFF Input Logic Low Voltage
V
IN
=2.7V-5.5V
4
0.8
V
V
IH
ON/OFF Input Logic High Voltage
V
IN
=2.7V to
4.2V
2
V
V
IN
= >4.2V to 5.5V
2.4
V
I
SINK
ON/OFF Input Leakage
V
ON/OFF
= 5.5V
1
uA
AAT4280-1
T
D(ON)
Output Turn-On Delay
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
20
40
uS
T
ON
Output Turn-On rise time
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
1000
1500
uS
T
D(OFF)
Output Turn-Off delay time
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
4
10
uS
AAT4280-2
T
D(ON)
Output Turn-On Delay
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
0.5
2
uS
T
ON
Output Turn-On rise time
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
0.5
1
uS
T
D(OFF)
Output Turn-Off delay time
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
4
10
uS
AAT4280-3
T
D(ON)
Output Turn-On Delay
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
20
40
uS
T
ON
Output Turn-On rise time
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
100
150
uS
T
D(OFF)
Out
put Turn_Off delay time
V
IN
=5V, R
LOAD
=10
, T
A
=25 C
4
10
uS
R
PD
Output pull-down resistance during OFF ON/OFF = inactive, T
A
=25 C
150
250
AAT4280
Slew Rate Controlled Load Switch
4
4280.2002.2.0.92
Typical Characteristics
(Unless otherwise noted, V
IN
= 5V, T
A
= 25C)
Off Switch Current vs. Temperature
0.001
0.010
0.100
1.000
-40
-20
0
20
40
60
80
100
Temperature (
C)
I
OFFSW
(
A)
ON/OFF Threshold vs. V
IN
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
V
IN
(V)
ON/OFF Threshold (V)
V
IH
V
IL
R
DS(ON)
vs. Temperature
40
50
60
70
80
90
100
110
120
-40
-20
0
20
40
60
80
100
Temperature (
C)
R
DS(ON)
(m
)
V
IN
=5V
V
IN
=3V
R
DS(ON)
vs. V
IN
70
90
110
130
150
170
190
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
V
IN
(V)
R
DS(ON)
(m
)
2A
1A
500mA
100mA
Quiescent Current vs. Input Voltage
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0
1
2
3
4
5
6
V
IN
(V)
Quiescent Current (
A)
Quiescent Current vs. Temperature
0
1
2
3
4
-40
-20
0
20
40
60
80
100
Temperature (
C)
I
Q
(
A)
V
IN
=5V
V
IN
=3V
AAT4280
Slew Rate Controlled Load Switch
4280.2002.2.0.92
5
Typical Characteristics--4280-1
(Unless otherwise noted, V
IN
= 5V, T
A
= 25C)
AAT4280-1 Turn-Off
V
IN
=5V R
L
=10
Time (10
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-1 Turn-Off
V
IN
=3V R
L
=6
Time (10
s/div)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-1 Turn-On
V
IN
=5V R
L
=10
Time (500
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-1 Turn-On
V
IN
=3V R
L
=6
Time (500
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280
Slew Rate Controlled Load Switch
6
4280.2002.2.0.92
AAT4280
Slew Rate Controlled Load Switch
4280.2002.2.0.92
7
Typical Characteristics--4280-2
(Unless otherwise noted, V
IN
= 5V, T
A
= 25C)
AAT4280-2 Turn-Off
V
IN
=5V R
L
=10
Time (5
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-2 Turn-Off
V
IN
=3V R
L
=6
Time (5
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-2 Turn-On
V
IN
=5V R
L
=10
Time (5
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-2 Turn-On
V
IN
=3V R
L
=6
Time (5
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
Typical Characteristics--4280-3
(Unless otherwise noted, V
IN
= 5V, T
A
= 25C)
AAT4280-3 Turn-Off
V
IN
=5V R
L
=10
Time (5
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-3 Turn-Off
V
IN
=3V R
L
=6
Time (5
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-3 Turn-On
V
IN
=5V R
L
=10
Time (50
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280-3 Turn-On
V
IN
=3V R
L
=6
Time (50
s/div.)
ON/OFF (5V/div.)
V
OUT
(2V/div.)
I
IN
(200mA/div.)
AAT4280
Slew Rate Controlled Load Switch
8
4280.2002.2.0.92
Functional Description
The AAT4280 is a family of flexible P-channel
MOSFET power switches designed for high-side
load-switching applications. There are three ver-
sions of AAT4280 with different turn-on and turn-off
characteristics to choose from, depending upon the
specific requirements of an application. The first
AAT4280-1 version has a moderate turn on slew
rate feature, which reduces in-rush current when
the MOSFET is turned on. This function 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 reach-
es 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 device ver-
sion, the AAT4280-2 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 AAT4280-3 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 AAT4280 operate with input volt-
ages ranging from 1.8V to 5.5V. All versions of this
device have extremely low operating current, mak-
ing them ideal for battery-powered applications. In
cases where the input voltage drops below 1.8V,
the AAT4280 MOSFET device is protected from
entering into the saturation region of operation by
automatically shutting down through an under volt-
age lockout control circuit. The ON/OFF control pin
is TTL compatible and will also function with 2.5
volt to 5 volt logic systems, making the AAT4280 an
ideal level shifting load-switch.
AAT4280
Slew Rate Controlled Load Switch
4280.2002.2.0.92
9
Functional Block Diagram
Under
Voltage
Lockout
Level
Shift
IN
ON/OFF
OUT
GND
Turn-On
Slew Rate
Control
*
*AAT4280-3 only
AAT4280
Slew Rate Controlled Load Switch
10
4280.2002.2.0.92
Applications Information
Input Capacitor
Typically a 1F or larger capacitor is recommend-
ed for C
IN
in most applications. A C
IN
capacitor is
not required for basic operation. However, C
IN
is
useful in preventing load transients from affecting
upstream circuits. C
IN
should be located as close
to the device V
IN
pin as practically possible.
Ceramic, tantalum or aluminum electrolytic capaci-
tors may be selected for C
IN
. There is no specific
capacitor ESR requirement for C
IN
. However, for
higher current operation, ceramic capacitors are
recommended for C
IN
due to their inherent capabil-
ity over tantalum capacitors to withstand input cur-
rent surges from low impedance sources such as
batteries in portable devices.
Output Capacitor
For proper slew operation, a 0.1F capacitor or
greater between V
OUT
and GND is recommended.
The output capacitor has no specific capacitor type
or ESR requirement. If desired, C
OUT
may be
increased without limit to accommodate any load
transient condition without adversely affecting the
device turn on slew rate time.
Enable Function
The AAT4280 features an enable / disable function.
This pin (ON/OFF) is compatible with both TTL or
CMOS logic.
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
the internal parasitic diode and allow excessive
current flow into the V
OUT
pin and possible damage
to the load switch.
In applications where there is a possibility of V
OUT
exceeding V
IN
for brief periods of time during nor-
mal operation, the use of a larger value C
IN
capaci-
tor is highly recommended. A larger value of C
IN
with respect to C
OUT
will effect a slower C
IN
decay
rate during shutdown, thus preventing V
OUT
from
exceeding V
IN
. In applications where there is a
greater danger of V
OUT
exceeding V
IN
for extended
periods of time, it is recommended to place a schot-
tky diode from V
IN
to V
OUT
(connecting the cathode
to V
IN
and anode to V
OUT
). The Schottky diode for-
ward voltage should be less then 0.45 volts.
Thermal Considerations and High
Output Current Applications
The AAT4280 is designed to deliver a continuous
output load current. The limiting characteristic for
maximum safe operating output load current is
package power dissipation. In order to obtain high
operating currents, careful device layout and circuit
operating conditions need to be taken into account.
The following discussions will assume the load
switch is mounted on a printed circuit board utiliz-
ing the minimum recommended footprint as stated
in the layout considerations section.
At any given ambient temperature (T
A
) the maxi-
mum package power dissipation can be deter-
mined by the following equation:
P
D(MAX)
= [T
J(MAX)
- T
A
] /
JA
Constants for the AAT4280 are maximum junction
temperature, T
J(MAX)
= 125C, and package thermal
resistance,
JA
= 120C/W. Worst case conditions
are calculated at the maximum operating tempera-
ture where T
A
= 85C. Typical conditions are cal-
culated under normal ambient conditions where T
A
= 25C. At T
A
= 85C, P
D(MAX)
= 333mW. At T
A
=
25C, P
D(MAX)
= 833mW.
The maximum continuous output current for the
AAT4280 is a function of the package power dissi-
pation and the R
DS
of the MOSFET at T
J(MAX)
. The
maximum R
DS
of the MOSFET at T
J(MAX)
is calcu-
lated by increasing the maximum room temperature
R
DS
by the R
DS
temperature coefficient. The tem-
perature coefficient (T
C
) is 2800ppm/C. Therefore,
MAX R
DS
125C = R
DS
25C
(1 + T
C
T)
MAX R
DS
125C = 120m
(1 + 0.0028
(125C - 25C)) = 154m
AAT4280
Slew Rate Controlled Load Switch
4280.2002.2.0.92
11
For maximum current, refer to the following equation:
I
OUT(MAX)
< ( P
D(MAX)
/ R
DS
)
1/2
For example, if V
IN
= 5V, R
DS(MAX)
=154m
and T
A
= 25C, I
OUT(MAX)
= 2.3A. If the output load current
were to exceed 2.3A or if the ambient temperature
were to increase, the internal die temperature will
increase, and the device will be damaged.
Higher peak currents can be obtained with the
AAT4280. To accomplish this, the device thermal
resistance must be reduced by increasing the heat
sink area or by operating the load switch in a duty
cycle manner.
High Peak Output Current Applications
Some applications require the load switch to oper-
ate at a continuous nominal current level with short
duration high current peaks. The duty cycle for
both output current levels must be taken into
account. To do so, first calculate the power dissi-
pation at the nominal continuous current level, and
then add in the additional power dissipation due to
the short duration high current peak scaled by the
duty factor.
For example, a 4V system using an AAT4280 oper-
ates at a continuous 100mA load current level and
has short 2A current peaks, as in a GSM applica-
tion. The current peak occurs for 576s out of a
4.61ms period.
First, the current duty cycle is calculated:
% Peak Duty Cycle: X/100 = 576s/4.61ms
% Peak Duty Cycle = 12.5%
The load current is 100mA for 87.5% of the 4.61ms
period and 2A for 12.5% of the period. Since the
Electrical Characteristics do not report R
DS(MAX)
for
4 volt operation, it must be calculated approxi-
mately by consulting the chart of R
DS(ON)
vs. V
IN
.
The R
DS
reported for 5 volts can be scaled by the
ratio seen in the chart to derive the R
DS
for a 4 volt
V
IN
: 120m
87m
/80m
= 130m
. De-rated
for temperature: 130m
x (1 + .0028
(125C -
25C)) = 166m
. The power dissipation for a
100mA load is calculated as follows:
P
D(MAX)
= I
OUT
2
R
DS
P
D(100mA)
= (100mA)
2
166m
P
D(100mA)
= 1.66mW
P
D(87.5%D/C)
= %DC
P
D(100mA)
P
D(87.5%D/C)
= 0.875
1.66mW
P
D(87.5%D/C)
= 1.45mW
The power dissipation for 100mA load at 87.5%
duty cycle is 1.45mW. Now the power dissipation
for the remaining 12.5% of the duty cycle at 2A is
calculated:
P
D(MAX)
= I
OUT
2
R
DS
P
D(2A)
= (2A)
2
166m
P
D(2A)
= 664mW
P
D(12.5%D/C)
= %DC
P
D(2A)
P
D(12.5%D/C)
= 0.125
664mW
P
D(12.5%D/C)
= 83mW
The power dissipation for 2A load at 12.5% duty
cycle is 83mW. Finally, the two power figures are
summed to determine the total true power dissipa-
tion under the varied load.
P
D(total)
= P
D(100mA)
+ P
D(2A)
P
D(total)
= 1.45mW + 83mW
P
D(total)
= 84.5mW
The maximum power dissipation for the AAT4280
operating at an ambient temperature of 85C is
333mW. The device in this example will have a
total power dissipation of 84.5mW. This is well with
in the thermal limits for safe operation of the
device, in fact, at 85C, the AAT4280 will handle a
2A pulse for up to 50% duty cycle. At lower ambi-
ent temperatures the duty cycle can be further
increased.
Figure 1: Evaluation board
Figure 2: Evaluation board
Figure 3: Evaluation board
top side silk screen layout /
component side layout
solder side layout
assembly drawing
AAT4280
Slew Rate Controlled Load Switch
12
4280.2002.2.0.92
Printed Circuit Board Layout
Recommendations
For proper thermal management, and to take
advantage of the low R
DS(ON)
of the AAT4280, a few
circuit board layout rules should be followed: V
IN
and V
OUT
should be routed using wider than normal
traces, and GND should be connected to a ground
plane. To maximize package thermal dispation and
power handling capacity of the AAT4280 SOT23-6/
SC70JW-8 package, the ground plane area con-
nected to the ground pins should be made as large
as possible. For best performance, C
IN
and C
OUT
should be placed close to the package pins.
Evaluation Board Layout
The AAT4280 evaluation layout follows the printed
circuit board layout recommendations, and can be
used for good applications layout. Refer to Figures
1 through 3.
Note: Board layout shown is not to scale.
Ordering Information
Package Information
SOT23-6
A1
b
A2
A
E
D
f
L2
t
L
C
GAUGE PLANE
e1
e
Device Option
Package
Marking
Part Number
Bulk
Tape and Reel
AAT4280-1
SOT23-6
N/A
AAT4280IGU-1-T1
AAT4280-2
SOT23-6
N/A
AAT4280IGU-2-T1
AAT4280-3
SOT23-6
N/A
AAT4280IGU-3-T1
AAT4280-1
SC70JW-8
N/A
AAT4280IJS-1-T1
AAT4280-2
SC70JW-8
N/A
AAT4280IJS-2-T1
AAT4280-3
SC70JW-8
N/A
AAT4280IJS-3-T1
AAT4280
Slew Rate Controlled Load Switch
4280.2002.2.0.92
13
Dim
Millimeters
Inches
Min
Max
Min
Max
A
1.00
1.30
0.039
0.051
A1
0.00
0.10
0.000
0.004
A2
0.70
0.90
0.028
0.035
b
0.35
0.50
0.014
0.020
c
0.10
0.25
0.004
0.010
D
2.70
3.10
0.106
0.122
E1.40
1.80
0.055
0.071
e
1.90
0.075
H
2.60
3.00
0.102
0.118
L
0.37
0.015
S
0.45
0.55
0.018
0.022
S1
0.85
1.05
0.033
0.041
1
9
1
9
SC70JW-8
1
D
A
A2
b
E
e
e
e
L
E1
A1
c
0.048REF
AAT4280
Slew Rate Controlled Load Switch
14
4280.2002.2.0.92
Advanced Analogic Technologies, Inc.
1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086
Phone (408) 524-9684
Fax (408) 524-9689
Dim
Millimeters
Inches
Min
Max
Min
Max
E2.10 BSC
0.083 BSC
E1
1.75
2.00
0.069
0.079
L
0.23
0.40
0.009
0.016
A
1.10
0.043
A1
0
0.10
0.004
A2
0.70
1.00
0.028
0.039
D
2.00 BSC
0.079 BSC
e
0.50 BSC
0.020 BSC
b
0.15
0.30
0.006
0.012
c
0.10
0.20
0.004
0.008
0
8
0
8
1
4
10
4
10
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