SmartSwitch™
AAT4601A
1.8A Current Limited P-Channel Switch
4601A.2004.07.1.2 1
General Description
The AAT4601A SmartSwitch™ is part of
AnalogicTech™'s Application Specific Power
MOSFET™ (ASPM™) product family. It is a 1.8A
Current Limited P-channel MOSFET power switch
designed for high-side load-switching applications.
This switch operates with inputs ranging from 2.7V
to 5.5V, making it ideal for both 3V and 5V systems.
An integrated current-limiting circuit protects the
input supply against large changes in load current
which could cause the supply to fall out of regula-
tion. The AAT4601A has protection from thermal
overload which limits power dissipation and junction
temperatures. The maximum current limit level will
guarantee 1.8A can be delivered to the load; the
actual threshold is programmed with a resistor from
the SET pin to ground. The quiescent supply cur-
rent is typically 12µA. In shutdown mode, the sup-
ply current decreases to less than 1µA.
The AAT4601A is available in 8-pin SOP, TSSOP,
or MSOP specified over -40 to 85°C.
Features
• 2.7V to 5.5V Input voltage range
• Programmable over current threshold
• Low quiescent current
• 12µA typical
• Less than 1µA with Switch off
• Only 2.5V needed for ON Control
• Thermal Shutdown
• Fault Flag
• 2ms Fault Blanking
• Undervoltage Lockout
• Temperature range -40 to 85°C
• 2kV ESD rating
• UL Approved—File No. E217765
• 8-pin SOP, TSSOP, or MSOP package
Applications
• USB ports
• Notebook computers
• Peripheral ports
• Hot swap supplies
UL Recognized Component
Typical Application
AAT4601A
ON
IN OUT
SET
GND
ON
1µF
100kΩ
R
SET
1uF
INPUT OUTPUT
IN OUT
FAULT
1
2
8
3
6
7
5
4
Pin Descriptions
Pin Configuration
SOP-8 MSOP-8
(Top View) (Top View)
TSSOP-8
(Top View)
IN
IN
ON
GND
FAUL
T
OUT
OUT
SET
4
3
2
1
5
6
7
8
1 2
OUT
FAULT
OUT
SET
IN
IN
ON
GND
1
2
3
4
8
7
6
5
1 2
OUT
FAULT
OUT
SET
IN
IN
ON
GND
1
2
3
4
8
7
6
5
Pin # Symbol Function
1,2 IN These pins are the input to the P-channel MOSFET source. Connect a
1µF capacitor from IN to GND.
3 ON Active-Low Enable Input. A logic low turns the switch on.
4 GND Ground
5 SET Current-Limit Set Input. A resistor from SET to ground sets the current
limit for the switch.
6,7 OUT These pins are the P-channel MOSFET drain connection. Connect a 1µF
capacitor from OUT to GND.
8 FAULT Fault-Indication Output. This open-drain output goes low when in current
limit or when the die temperature exceeds +135 ºC, with a 2ms delay
after the fault event occurs.
AAT4601A
1.8A Current Limited P-Channel Switch
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AAT4601A
1.8A Current Limited P-Channel Switch
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Absolute Maximum Ratings (TA=25°C 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 1.5kΩresistor into each pin.
Thermal Characteristics
Note 2: Mounted on an FR4 printed circuit board.
Symbol Description Value Units
ΘJA Maximum Thermal Resistance (SOP-8) 2100 °C/W
ΘJA Maximum Thermal Resistance (TSSOP-8) 2150 °C/W
ΘJA Maximum Thermal Resistance (MSOP-8) 2150 °C/W
PDMaximum Power Dissipation (SOP-8) 21.25 W
PDMaximum Power Dissipation (TSSOP-8) 2833 mW
PDMaximum Power Dissipation (MSOP-8) 2833 mW
Symbol Description Value Units
VIN IN to GND -0.3 to 6 V
VON, VFAULT ON, FAULT to GND -0.3 to VIN+0.3 V
VSET, VOUT SET, OUT to GND -0.3 to VIN+0.3 V
IMAX Maximum Continuous Switch Current 3 A
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at Leads) 300 °C
VESD ESD Rating—HBM14000 V
AAT4601A
1.8A Current Limited P-Channel Switch
44601A.2004.07.1.2
Electrical Characteristics (VIN = 5V, TA= -40 to 85°C unless otherwise noted. Typical values
are at TA=25°C)
Note 3: Guaranteed by design.
Symbol Description Conditions Min Typ Max Units
VIN Operation Voltage 2.7 5.5 V
IQQuiescent Current VIN = 5V, ON = GND, IOUT = 0 12 30 µA
IQ(OFF) Off Supply Current ON=IN, VIN = 5.5V .004 1 µA
ISD(OFF) Off Switch Current ON = IN, VIN = 5.5V, VOUT = 0 .07 15 µA
VUVLO Undervoltage Lockout Rising edge, 1% hysteresis, 2.0 2.3 2.7 V
VIN=5.0V 70
RDS(ON) On-Resistance VIN=4.5V 75 130
VIN=3.0V 80 150 mΩ
VIN=3.0V, TA=25°C 80 110
ILIM Current Limit RSET = 20.5kΩ750 1000 1250 mA
ILIM(MIN) Minimum Current Limit 260 mA
OTMP Shutdown Temperature VIN = 5V 125 ºC
VONL ON Input Low Voltage 0.8 V
VONH ON Input High Voltage VIN=2.7V to 3.6V 2.0
VIN=4.5V to 5.5V 2.4 V
IONSINK ON Input leakage VON = 5.5V 0.01 1 µA
VFAULTL FAULT Logic Output Low Voltage ISINK=1mA 0.08 0.4 V
IFSINK FAULT Logic Output High Leakage VFAULT = 5.5V 0.05 1 µA
TRESP Current Limit Response Time VIN=5V 2 µs
TBLANK Fault Blanking Time after Turn-On 2 ms
TOFF Turn-Off Time3VIN=5V 20 µs
TON Turn-On Time3VIN=5V 200 µs
Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA= 25°C)
Off-Switch Current vs. Temperature
1
0.1
0.01
0.001
0.0001
10
-40 -20 0 20 40 60 80 100 120 140
Temperature (°C)
Off-Switch Current (µA)
Off-Supply Current vs. Temperature
0.0001
0.001
0.01
0.1
1
10
-40 -20 0 20 40 60 80 100 120 140
Temperature
Off-Supply Current (µA)
(°C)
RSET * ILIM Product vs. ILIM
Typical I LIM
(A)
Product (V)
18000
19000
20000
21000
22000
23000
24000
25000
0.0 0.5 1.0 1.5 2.0 2.5
Current Limit (VIN = 5.0V)
Output (V)
Output (A)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
01 23 45
RSET = 20.5kΩ
Input Voltage = 5V
0
0123456
5
10
15
20
25
Quiescent Current
Input (V)
Input (µA)
Quiescent Current vs. Temperature
0
5
10
15
20
25
-40 -20 0 20 40 60 80 100 120
Temperature
Quiescent Current (µA)
(°C)
AAT4601A
1.8A Current Limited P-Channel Switch
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1.8A Current Limited P-Channel Switch
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Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA= 25°C)
Short Circuit through 0.6Ω
0
2
4
6
8
-20 0 20 40 60 80 100 120 140
Time (µs)
Input and Output
-3
0
3
6
9
Output (A)
Output Current
Input Voltage
Output Voltage
(V)
Short Circuit through 0.3Ω
0
2
4
6
8
02468
Time (µs)
Input and Output
-4
0
4
8
12
Output (A)
Output Current
Input Voltage
Output Voltage
(V)
Switch Turn-Off Time
-1
0
1
2
3
4
5
6
-4-20246
Time (
Voltage (V)
Output
ON
IOUT =I
LIMIT
Switch Turn-On Time
-1
0
1
2
3
4
5
6
-20 -10 0 40 60 80
Time (
Voltage (V)
Output
ON
IOUT =I LIMIT
Turn-Off vs. Temperature
0
0.2
0.4
0.6
0.8
1
1.8
1.6
1.4
1.2
2
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Turn-OFF Time (µs)
VIN=5V
VIN=3V
Turn-On vs. Temperature
0
10
20
30
40
50
60
70
80
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Turn-ON Time (µs)
VIN=3V
VIN=5V
Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA= 25°C)
RDS(ON) vs. Temperature
40
50
60
70
80
90
100
-40 -20 0 20 40 60 80
Temperature (°C)
RDS(ON) (mΩ
)
VIN=4.5V
VIN=3V
Fault Delay vs. Temperature
0
0.5
1.0
1.5
2.0
2.5
-40 -20 0 20 40 60 80 100
Temperature (°C)
Fault Delay (ms)
AAT4601A
1.8A Current Limited P-Channel Switch
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AAT4601A
1.8A Current Limited P-Channel Switch
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Functional Block Diagram
IN
ON
SET
FAULT
OUT
Under-
voltage
Lockout
Over-temp
Protection
1.2V
Reference
Current
Limit
Functional Description
The AAT4601A is an integrated MOSFET load
switch with an adjustable current limit, over tem-
perature protection, level shifted input and a fault
flag. The current limit control is combined with an
over temperature thermal limit circuit to provide a
comprehensive system to protect the load switch
under short circuit or other adverse operating con-
ditions. The AAT4601A is ideally suited for control
and protection of peripheral ports such as USB,
RS232 and parallel ports.
The current limit and over temperature circuits will
act independently. The device current limit is acti-
vated when the output load current exceeds an
internal threshold level. The internal current limit
threshold is determined by an external resistor
connected between the SET pin and ground. The
minimum current limit threshold is specified by
ILIM(MIN). If the load switch ambient temperature
becomes excessive or if a short circuit condition
persists, the die temperature will rise causing the
over temperature protection circuit to activate.
If a current limit level less than ILIM(MIN) is required,
the AAT4601A can be used to operate in foldback
current limit mode. To achieve this, an RSET value
can be chosen to program a current limit lower
than ILIM(MIN); in this case, when the load current
reaches ILIM(MIN), the current will immediately drop,
limiting at the programmed value.
If the current limit or over temperature protection
circuits are active for more then two milliseconds,
the system will be informed via the FAULT Flag.
The two millisecond delay allows the AAT4601A to
be turned on into capacitive loads without activat-
ing the FAULT Flag. The open drain FAULT output
can be connected directly to system controllers
driven by voltage levels less than the IN pin voltage
without additional level shifting circuitry.
The load switch is turned off by applying a logic high
level to the ON pin. The AAT4601A typically con-
sumes 12µA when operating, when off, the device
draws less then 1µA. In the off state, current is pre-
vented from flowing between the input and output.
The ON function has logic level thresholds that
allow the AAT4601A to be TTL compatible and may
also be controlled by 2.5V to 5.0V CMOS circuits.
The voltage level on either ON or FAULT should not
exceed the input supply level present on the IN pin.
Applications Information
Setting Current Limit
A simple three-step procedure can be used to
adjust the AAT4601A's current limit. First, the max-
imum current required by the load should be deter-
mined. Second, select a resistor that guarantees
adequate current is available to the load under nor-
mal conditions. Finally, the maximum current that
can pass through the switch can be calculated and
compared to the maximum current available.
Step 1: The maximum current required by a load
is usually defined in port specifications design
application references. For example, USB ports
are specified to support loads of up to 500 mA.
Step 2: The most convenient method for deter-
mining a current limit resistor value is to look it up
in the provided table named "Current Limit RSET
Values". Find the lowest current value that is
greater than the maximum load current in the given
application. Refer to the column named "Device
will not current limit below". The resistor value
needed is in the corresponding row named "RSET".
For example, a USB port requires 500 mA. The
lowest level where the device will current limit
above 500 mA is 507 mA. The corresponding
resistor value for RSET would be 33kΩ.
Step 3: Now the required resistor value has been
determined. The maximum current that can be
drawn, even with a short circuit applied to the out-
put, can be determined by reading the column
labeled "Device always current limits below". If the
power supply connected to the AAT4601A's input
can provide this current level, the power supply volt-
age will not collapse when a short circuit is applied
to the load switch output. For example, a notebook
computer has a USB port which is powered by an
AAT4601A with a 33kΩresistor connected between
the SET pin and GND. If the power supply con-
nected to the AAT4601A's IN pin can provide more
than 845 mA, this supply will remain in regulation
even if a short circuit is applied to the USB port.
Current Limit RSET Values
AAT4601A
1.8A Current Limited P-Channel Switch
4601A.2004.07.1.2 9
RSET Current Device will Device always
(kΩ) Limit typ not current current limits
(mA) limit below: below:
(mA) (mA)
7.5 2476 1857 3095
8.2 2277 1708 2847
9.1 2065 1549 2581
10 1895 1421 2369
11 1748 1311 2185
12 1633 1224 2041
13 1528 1146 1910
15 1353 1015 1691
16 1280 960 1600
18 1158 869 1448
20 1055 791 1318
22 972 729 1215
24 897 673 1122
27 811 608 1014
30 736 552 919
33 676 507 845
36 625 469 781
39 582 436 727
43 533 400 666
47 491 368 613
51 455 341 568
56 418 314 523
62 380 285 476
68 350 262 437
75 320 240 400
82 295 221 369
91 267 200 334
100 245 183 306
110 223 167 279
120 206 155 258
130 192 144 239
150 167 125 209
160 157 118 197
AAT4601A
1.8A Current Limited P-Channel Switch
10 4601A.2004.07.1.2
Applications Information
Operation in Current Limit
If an excessive load is applied to the output of an
AAT4601A, the load's current will be limited by the
AAT4601A's current limit circuitry. Refer to the figure
named "Overload Operation". If a short circuit were to
occur on the load, it would demand more current than
what is allowed by the internal current limiting circuit
and the voltage at the AAT4601A's output will drop.
This causes the AAT4601A to dissipate more power
than in normal operation, causing the die temperature
to increase. When die temperature exceeds the inter-
nal over temperature threshold, the AAT4601A will
shut down. After shutting down, the AAT4601A cools
to a level below the over temperature threshold, at
which point it will start up again. The AAT4601A will
continue to cycle off and on until one of the following
events occurs; the load current is reduced to a level
below the AAT4601A's current limit setting, the input
power is removed, or until the output is turned off by
a logic high level applied to the ON pin.
Thermal Considerations
Since the AAT4601A has internal current limit and
over temperature protection, junction temperature is
rarely a concern. If an application requires a large
load current in a high temperature operating envi-
ronment, there is the possibility that the over tem-
perature protection circuit rather than the current
limit circuit will regulate the current available to the
load. In these applications, the maximum current
available without risk of activation of the over tem-
perature circuit can be calculated. The maximum
internal temperature while current limit is not active
can be calculated using Equation 1:
TJ(MAX) = IMAX2×RDS(ON)(MAX) ×RθJA + TA(MAX)
In Equation 1, IMAX is the maximum current required
by the load. RDS(ON)(MAX) is the maximum rated
RDS(ON) of the AAT4601A at high temperature. RθJA is
the thermal resistance between the AAT4601A's die
and the board onto which it is mounted. TA(MAX) is
the maximum ambient temperature for the printed cir-
cuit board assembly under the AAT4601A when the
load switch is not dissipating power. Equation 1 can
be transformed to provide IMAX; Refer to Equation 2.
IMAX=TSD(MIN) - TA(MAX)
RDS(ON)(MAX) ×RθJA
TSD(MIN) is the minimum temperature required to
activate the AAT4601A's over temperature protec-
tion. With typical specification of 125°C, 115°C is a
safe minimum value to use.
For example, a portable device is specified to oper-
ate in a 50°C environment. The printed circuit
board assembly will operate at temperatures as
high as 85°C. This portable device has a sealed
case and the area of the printed board assembly is
rellatively small causing RθJA to be approximately
120°C/W. Using Equation 2,
IMAX=115 - 85 = 1.4 A
130 ×120
If this system requires less than 1.4 A, the thermal
limit will not activate during normal operation.
Overload Operation
0
1
2
3
4
5
6
-0.5 0 0.5 1 1.5 2
Time (s)
Voltage (V)
Output Voltage
Input Voltage
1 Ω is applied to output at t = 0
RSET is 33 kΩ
Applications Information
Input Capacitor
The input capacitor serves two purposes. First, it
protects the source power supply from transient
current effects generated by the application load
circuit. If a short circuit is suddenly applied to the
output of an AAT4601A, there is a microsecond long
period during which a large can current flow before
the current limit circuitry activates. Refer to the
characteristic curve named "Short Circuit Through
0.3Ω." A properly sized input capacitor can dramat-
ically reduce the load switch input transient
response effects seen by the power supply and
other circuitry upstream from the AAT4601A.
The second purpose of the input capacitor is to
prevent transient events generated by the load cir-
cuit from affecting the operation of the AAT4601A.
For example, if an AAT4601A is used in a circuit
that operates from a 3 volt power supply with poor
step load response, it is possible that turning on the
load switch could cause the input power supply to
droop below the AAT4601A's under voltage lockout
threshold. This drop in voltage would cause the
AAT4601A to turn off until the input power supply's
voltage recovers. Since this cycle would be self-
perpetuating, the entire circuit could be seen to be
unstable. In the very rare case where capacitor
cost is prohibitive, the output load circuit should be
slew rate limited when turned on.
Output Capacitor
In order to insure stability while the device current
limit is active, a small capacitance of approximately
1µF should be used. When the AAT4601A is acti-
vated using the ON function, there are no momen-
tary current transients as in the case of when a short
circuit suddenly applied to a device that is already
on. Refer to the characteristic curve named "Switch
Turn-On Time." No matter how big the output
capacitor, output current is limited to the value
allowed by the threshold determined by RSET and
the internal current limiting circuitry. This permits
very large output capacitors to be used.
For example, USB ports are specified to have at least
120µF of down stream capacitance from their con-
trolling power switch. An output capacitance as large
as 1000µF would not disturb the input power supply
to the AAT4601A used to control the USB port.
ON Input
When the AAT4601A is in the off state, the output
is an open circuit and the device quiecent current
consumption is reduced to less than 1µA. The ON
threshold voltage is set to allow the AAT4601A to
be controlled by 5 volt TTL levels as well as CMOS
power from 2.5 volts to 5 volts. The ON function
control voltage level should not exceed the input
supply level applied to the IN pin.
FAULT Output
A FAULT flag is provided to alert a system if the load
switch is not receiving a sufficient voltage level to
operate properly. If either the current limit or over
temperature circuits in any combination are active
for more than approximately two milliseconds con-
tinuously, the FAULT pin is pulled to ground inter-
nally through a 100Ωresistance. The 2 millisecond
delay on the FAULT function is intended to prevent
capacitive loads connected to the load switch out-
put from activating FAULT when the device is
turned on. The placement of a pull up resistor
between the FAULT pin and the IN pin is recom-
mended. Reasonable values for the pull up resistor
should range from 10kΩto 100kΩ. Since FAULT is
an open drain terminal, it may be pulled up to any
voltage that is not greater than the level present on
the IN pin. This is done to allow the AAT4601A to
signal ancillary circuitry that is powered by voltage
level less than the level on the IN pin.
Reverse Voltage
The AAT4601A is designed to control current flow-
ing from IN to OUT. If a voltage is applied to OUT
which is greater than that on IN, a large resulting
reverse current may flow, potentially damaging the
AAT4601A.
AAT4601A
1.8A Current Limited P-Channel Switch
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AAT4601A
1.8A Current Limited P-Channel Switch
12 4601A.2004.07.1.2
Figure 1: AAT4601A Evaluation Figure 2: AAT4601A Evaluation Figure 3: AAT4601A Evaluation
board top side silk screen board component side layout board solder side layout
assembly drawing
Printed Circuit Board Layout
Recommendations
For proper thermal management, and to take
advantage of the low RDS(ON) of the AAT4601A, a
few circuit board layout rules should be followed:
VIN and VOUT should be routed using wider than
normal traces, and GND should be connected to a
ground plane. For best performance, CIN and COUT
should be placed close to the package pins.
Evaluation Board Layout
The AAT4601A evaluation layout follows the print-
ed circuit board layout recommendations, and can
be used for good applications layout.
Note: Board layout shown is not to scale.
Ordering Information
Note 1: XYY = assembly and date code.
Package Information
SOP-8
All dimensions in millimeters.
0.175 ± 0.075 6.00 ± 0.20
3.90 ± 0.10
1.55 ± 0.20
1.27 BSC0.42 ± 0.09 × 8
4.90 ± 0.10
4° ± 4°
45°
0.375 ± 0.125
0.235 ± 0.045
0.825 ± 0.445
Package Marking1Part Number (Tape and Reel)
SOP-8 AAT4601AIAS-T1
TSSOP-8 AAT4601AIHS-T1
MSOP-8 MQXYY AAT4601AIKS-T1
AAT4601A
1.8A Current Limited P-Channel Switch
4601A.2004.07.1.2 13
TSSOP-8
All dimensions in millimeters.
DETAIL A
4.40 ± 0.10
6.40 ± 0.20
0.65 BSC
3.00 ± 0.10
0.245 ± 0.055 × 8 0.10 ± 0.05
0.60 ± 0.15
0.145 ± 0.055
1.05 MAX
1.20 MAX
4° ± 4°
12°
12° REF × 4
1.00
REF
AAT4601A
1.8A Current Limited P-Channel Switch
14 4601A.2004.07.1.2
MSOP-8
All dimensions in millimeters.
PIN 1
1.95 BSC
0.254 BSC
0.155 ± 0.075
0.60 ± 0.20
3.00 ± 0.10
0.95 ± 0.15
0.95 REF
0.85 ± 0.10
3.00 ± 0.10
10° ± 5°
4° ± 4°
0.65 BSC 0.30 ± 0.08
0.075 ± 0.075
4.90 ± 0.10
GAUGE PLANE
AAT4601A
1.8A Current Limited P-Channel Switch
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AAT4601A
1.8A Current Limited P-Channel Switch
16 4601A.2004.07.1.2
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
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