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1.8A Current Limited P-Channel Switch General Description
The AAT4601 SmartSwitch is a member of AnalogicTech's Application Specific Power MOSFETTM (ASPMTM) 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 regulation. The AAT4601 has protection from thermal overload which limits power dissipation and junction temperatures. The maximum current limit level will guarantee that 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 current is typically 12A. In shutdown mode, the supply current decreases to less than 1A. The AAT4601 is available in a Pb-free, 8-pin SOP, TSSOP, or MSOP package and is specified over the -40C to +85C temperature range.
AAT4601
Features
* * * * * * * * * * * *
SmartSwitchTM
Input Voltage: 2.7V to 5.5V Programmable Over-Current Threshold Low Quiescent Current -- 12A Typical -- Less Than 1A with Switch Off Only 2.5V Needed for ON Control Thermal Shutdown Fault Flag 2ms Fault Blanking Under-Voltage Lockout Temperature Range: -40C to +85C 4kV ESD Rating UL Approved--File No. E217765 8-Pin SOP, TSSOP, or MSOP Package
Applications
* * * * Hot Swap Supplies Notebook Computers Peripheral Ports USB Ports
UL Recognized Component
Typical Application
INPUT 100k
8
1 2
IN IN FAULT
OUT
6 7
OUTPUT
AAT4601
OUT SET
5
1F
ON
3
ON
1F R SET
GND
4
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1
1.8A Current Limited P-Channel Switch Pin Descriptions
Pin #
1, 2 3 4 5 6, 7 8
AAT4601
Symbol
IN ON (ON) GND (GND) SET OUT FAULT
Function
These pins are the input to the P-channel MOSFET source. Connect a 1F capacitor from IN to GND. Active low enable input. A logic low turns the switch on. Ground. Current limit set input. A resistor from SET to ground sets the current limit for the switch. These pins are the P-channel MOSFET drain connection. Connect a 1F capacitor from OUT to GND. Fault indication output. This open-drain output goes low when in current limit or when the die temperature exceeds +135C, with a 2ms delay after the fault event occurs.
Pin Configuration
SOP-8, MSOP-8 (Top View) TSSOP-8 (Top View)
IN IN ON GND
1
8
FAULT OUT OUT SET
1
IN IN ON GND
1 2 3 4
8 7 6 5
FAULT OUT OUT SET
2
7
2
3
6
4
5
2
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1.8A Current Limited P-Channel Switch Absolute Maximum Ratings1
TA = 25C, unless otherwise noted. Symbol
VIN VON, VFAULT VSET, VOUT IMAX TJ TLEAD VESD
AAT4601
Description
IN to GND ON, FAULT to GND SET, OUT to GND Maximum Continuous Switch Current Operating Junction Temperature Range Maximum Soldering Temperature (at Leads) ESD Rating--HBM2
Value
-0.3 to 6 -0.3 to VIN + 0.3 -0.3 to VIN + 0.3 3 -40 to 150 300 4000
Units
V V V A C C V
Thermal Characteristics3
Symbol
JA
Description
Maximum Thermal Resistance SOP-8 TSSOP-8 MSOP-8 SOP-8 TSSOP-8 MSOP-8
Value
100 150 150 1.25 833 833
Units
C/W W mW
PD
Maximum Power Dissipation
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin. 3. Mounted on an FR4 printed circuit board. 4601.2006.05.1.3
3
1.8A Current Limited P-Channel Switch Electrical Characteristics
VIN = 5V, TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol
VIN IQ IQ(OFF) ISD(OFF) VUVLO RDS(ON) ILIM ILIM(MIN) OTMP VONL VONH IONSINK VFAULTL IFSINK TRESP TBLANK TOFF TON
AAT4601
Description
Operation Voltage Quiescent Current Off-Supply Current Off-Switch Current Under-Voltage Lockout On Resistance Current Limit Minimum Current Limit Shutdown Temperature ON Input Low Voltage ON Input High Voltage ON Input leakage FAULT Logic Output Low Voltage FAULT Logic Output High Leakage Current Limit Response Time Fault Blanking Time After Turn-On Turn-Off Time1 Turn-On Time1
Conditions
VIN = 5V, ON = GND, IOUT = 0 ON = IN, VIN = 5.5V ON = IN, VIN = 5.5V, VOUT = 0 Rising Edge, 1% Hysteresis VIN = 5.0V VIN = 4.5V VIN = 3.0V VIN = 3.0V, TA = 25C RSET = 2k VIN = 5V VIN = 2.7V to 3.6V VIN = 4.5V to 5.5V VON = 5.5V ISINK =1mA VFAULT = 5.5V VIN = 5V VIN = 5V VIN = 5V
Min
2.7
Typ
12 0.004 0.07 2.3 70 75 80 80 715 375 125
Max
5.5 30 1 15 2.7 120 130 150 110 920
Units
V A A A V
2.0
m mA mA C V V
510
0.8 2.0 2.4 0.01 0.08 0.05 2 2 1 0.4 1
20 200
A V A s ms s s
1. Guaranteed by design.
4
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1.8A Current Limited P-Channel Switch Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25C.
Quiescent Current vs. Temperature
Quiescent Current (A)
25
AAT4601
Quiescent Current
25
Input Current (A)
-40 -20 0 20 40 60 80 100 120
20 15 10 5 0
20 15 10 5 0 0 1 2 3 4 5 6
Temperature (C)
Input Voltage (V)
Current Limit
(RSET = 2k; VIN = 5V)
1.0 2500
RSET ILIM Product vs. ILIM
Output Current (A)
0.8 0.6 0.4 0.2 0 0 1 2 3 4 5
2000
Product (V)
1500
1000
500 0 0.5 1 1.5 2
Output Voltage (V)
Typical ILIM (A)
Off-Supply Current vs. Temperature
Off-Supply Current (A)
10 1 0.1 0.01 0.001 0.0001 -40 -20 0 20 40 60 80 100 120 140
Off-Switch Current vs. Temperature
10
Off-Switch Current (A)
1 0.1 0.01 0.001 0.0001 -40
Temperature (C)
-20
0
20
40
60
80
100
120
140
Temperature (C)
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1.8A Current Limited P-Channel Switch Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25C.
Turn-On Time vs. Temperature
80
AAT4601
Turn-Off Time vs. Temperature
2.0
Turn-Off Time (s)
70
VIN = 3V
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0
VIN = 3V VIN = 5V
Turn-On Time (s)
60 50 40 30 20 10 0 -40 -20 0 20 40 60 80 100 120
VIN = 5V
-40
-20
0
20
40
60
80
100
120
Temperature (C)
Temperature (C)
Switch Turn-On Time
6 5
Switch Turn-Off Time
6 5
IOUT = ILIMIT
IOUT = ILIMIT
Voltage (V)
Voltage (V)
4 3 2 1 0 -1 -20
4 3 2 1 0 -1
ON Output
ON
Output
-10
0
40
60
80
-4
-2
0
2
4
6
Time (s)
Time (s)
Short-Circuit Through 0.3
Input and Output Voltage (V)
8 12
Short-Circuit Through 0.6
Input and Output Voltage (V)
8 9
Output Current
6
Output Current
6
Output Current (A)
Output Current (A)
Input Voltage
8
Input Voltage
6
4
4
4
3
2
0
2
0
Output Voltage
0 0 2 4 6 8 -4
Output Voltage
0 -20 0 20 40 60 80 100 120 -3 140
Time (s)
Time (s)
6
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1.8A Current Limited P-Channel Switch Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25C.
AAT4601
Fault Delay vs. Temperature
2.5
100 90
RDS(ON) vs. Temperature
Fault Delay (ms)
2.0
RDS(ON) (m)
80 70 60 50 40
1.5 1.0 0.5 0 -40
VIN = 3V
VIN = 4.5V
-20
0
20
40
60
80
100
-4 0
-20
0
20
40
60
80
Temperature (C)
Temperature (C)
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1.8A Current Limited P-Channel Switch Functional Block Diagram
AAT4601
IN
OUT
UnderVoltage Lockout
Over-Temperature Protection
FAULT ON
1.2V Reference Current Limit
SET
Functional Description
The AAT4601 is an integrated MOSFET load switch with an adjustable current limit, over-temperature 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 conditions. The AAT4601 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 activated 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 AAT4601 can be used to operate in foldback 8
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 than 2ms, the system will be informed via the FAULT flag. The 2ms delay allows the AAT4601 to be turned on into capacitive loads without activating 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 AAT4601 typically consumes 12A when operating; when off, the device draws less than 1A. In the off state, current is prevented from flowing between the input and output. The ON function has logic level thresholds that allow the AAT4601 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.
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1.8A Current Limited P-Channel Switch Applications Information
Setting Current Limit
A simple three-step procedure can be used to adjust the AAT4601's current limit. First, the maximum current required by the load should be determined. Second, select a resistor that guarantees adequate current is available to the load under normal 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 may be specified to support loads of up to 500mA. Step 2: The most convenient method for determining a current limit resistor value is to look it up in Table 1, "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, "Device Will Not Current Limit Below." The resistor value needed is in the corresponding row named "RSET." For example, a USB port requires 500mA. The lowest level where the device will current limit above 500mA is 516mA. The corresponding resistor value for RSET would be 2k. 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 output, can be determined by referring to the column labeled, "Device Always Current Limits Below." If the power supply connected to the AAT4601's input can provide this current level, the power supply voltage 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 AAT4601 with a 2k resistor connected between the SET pin and GND. If the power supply connected to the AAT4601's IN pin can provide more than 917mA, this supply will remain in regulation even if a short circuit is applied to the USB port. RSET ()
0 10 20 30 36 47 56 68 82 100 120 150 200 240 300 360 470 510 560 620 680 750 820 910 1000 1100 1200 1300 1500 1600 1800 2000 2200 2400 2700 3000 3300 3600 3900 4300 4700 5100 5600 6200 6800 7500
AAT4601
Current Device Will Not Device Always Limit Current Limit Current Limits Typ (mA) Below (mA) Below (mA)
2510 2463 2423 2386 2361 2332 2297 2258 2214 2161 2107 2028 1918 1840 1737 1649 1585 1529 1466 1397 1334 1266 1206 1144 1089 1034 986 941 865 829 769 716 673 633 582 539 502 470 442 410 382 358 332 306 283 268 1807 1773 1745 1718 1700 1679 1654 1626 1594 1556 1517 1460 1381 1325 1251 1187 1141 1101 1055 1006 960 911 869 823 784 745 710 677 623 597 554 516 485 456 419 388 362 339 318 295 275 258 239 220 204 193 3213 3152 3102 3054 3022 2985 2940 2890 2834 2766 2697 2596 2455 2355 2223 2111 2029 1957 1876 1788 1707 1620 1544 1464 1394 1324 1262 1204 1107 1061 985 917 861 811 745 690 643 602 565 524 489 458 424 392 362 343
Table 1: Current Limit RSET Values.
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1.8A Current Limited P-Channel Switch
Operation in Current Limit
If an excessive load is applied to the output of an AAT4601, the load current will be limited by the device's current limit circuitry. Refer to Figure 1, Overload Operation. If a short circuit were to occur on the load, it would demand more current than allowed by the internal current limiting circuit and the voltage at the AAT4601's output would drop. This causes the AAT4601 to dissipate more power than in normal operation, causing the die temperature to increase. When die temperature exceeds the internal over-temperature threshold, the AAT4601 will shut down. After shutting down, the AAT4601 cools to a level below the over-temperature threshold, at which point it will start up again. The AAT4601 will continue to cycle off and on until one of the following events occurs: the load current is reduced to a level below the AAT4601's current limit setting; the input power is removed; or the output is turned off by a logic high level applied to the ON pin. load. In these applications, the maximum current available without risk of activation of the over-temperature circuit can be calculated. The maximum internal temperature while current limit is not active can be calculated using Equation 1:
AAT4601
Eq. 1: TJ(MAX) = IMAX2 x RDS(ON)(MAX) x RJA + 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 AAT4601 at high temperature. RJA is the thermal resistance between the AAT4601's die and the board onto which it is mounted. TA(MAX) is the maximum ambient temperature for the printed circuit board assembly under the AAT4601 when the load switch is not dissipating power. Equation 1 can be transformed to provide IMAX; Refer to Equation 2:
Thermal Considerations
Since the AAT4601 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 environment, there is the possibility that the over-temperature protection circuit, rather than the current limit circuit, will regulate the current available to the
Eq. 2: IMAX =
TSD(MIN) - TA(MAX) RDS(ON)(MAX) x RJA
TSD(MIN) is the minimum temperature required to activate the AAT4601's over-temperature protection. With a typical specification of 125C, 115C is a safe minimum value to use.
6
5
Input Voltage
4
Voltage (V)
3
1 is Applied to Output at t = 0 RSET is 2k Output Voltage
2
1
0 -0.5
0
0.5
1
1.5
2
Time (s)
Figure 1: Overload Operation.
10
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1.8A Current Limited P-Channel Switch
For example, a portable device is specified to operate in a 50C environment. The printed circuit board assembly will operate at temperatures as high as 85C. This portable device has a sealed case and the area of the printed board assembly is relatively small, causing RJA to be approximately 120C/W. Using Equation 2: ed using the ON function, there are no momentary current transients, as in the case when a short circuit is suddenly applied to a device that is already on; refer to the characteristic curve, "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 120F of downstream capacitance from their controlling power switch. An output capacitance as large as 1000F would not disturb the input power supply to the AAT4601 used to control the USB port.
AAT4601
Eq. 3: IMAX =
115 - 85 = 1.4A 130 * 120
If this system requires less than 1.4A, the thermal limit will not activate during normal operation.
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 AAT4601, there is a microsecond-long period during which a large current can flow before the current limit circuitry activates; refer to the characteristic curve, "Short-Circuit Through 0.3." A properly sized input capacitor can dramatically reduce the load switch input transient response effects seen by the power supply and other circuitry upstream from the AAT4601. The second purpose of the input capacitor is to prevent transient events generated by the load circuit from affecting operation of the AAT4601. For example, if an AAT4601 is used in a circuit that operates from a 3V 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 AAT4601's under-voltage lockout threshold. This drop in voltage would cause the AAT4601 to turn off until the input power supply 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.
ON Input
When the AAT4601 is in the off state, the output is an open circuit and the device quiecent current consumption is reduced to less than 1A. The ON threshold voltage is set to allow the AAT4601 to be controlled by 5V TTL levels, as well as CMOS power from 2.5V to 5V. 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 properly operate. If either the current limit or overtemperature circuits in any combination are active for more than approximately 2ms continuously, the FAULT pin is pulled to ground internally through a 100 resistance. The 2ms delay on the FAULT function is intended to prevent capacitive loads connected to the load switch output 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 recommended. Reasonable values for the pull-up resistor should range from 10k to 100k. 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 AAT4601 to signal ancillary circuitry that is powered by a voltage level less than the level on the IN pin.
Output Capacitor
In order to insure stability while the device current limit is active, a small capacitance of approximately 1F should be used. When the AAT4601 is activat-
Reverse Voltage
The AAT4601 is designed to control current flowing from IN to OUT. If a voltage is applied to OUT 11
4601.2006.05.1.3
1.8A Current Limited P-Channel Switch
which is greater than that on IN, a large resulting reverse current may flow, potentially damaging the AAT4601. traces, and GND should be connected to a ground plane. For best performance, CIN and COUT should be placed close to the package pins.
AAT4601
Printed Circuit Board Layout Recommendations
For proper thermal management, and to take advantage of the low RDS(ON) of the AAT4601, a few circuit board layout rules should be followed: VIN and VOUT should be routed using wider than normal
Evaluation Board Layout
The AAT4601 evaluation layout follows the printed circuit board layout recommendations, and can be used for good applications layout. Note: Board layout shown is not to scale.
Figure 1: AAT4601 Evaluation Board Top Side Silk Screen Assembly Drawing.
Figure 2: AAT4601 Evaluation Board Component Side Layout.
Figure 3: AAT4601 Evaluation Board Solder Side Layout.
12
4601.2006.05.1.3
1.8A Current Limited P-Channel Switch Ordering Information
Package
SOP-8 TSSOP-8 MSOP-8
AAT4601
Marking1
4601 4601 IDXYY
Part Number (Tape and Reel)2
AAT4601IAS-T1 AAT4601IHS-T1 AAT4601IKS-T1
All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
SOP-8
3.90 0.10
4.90 0.10
6.00 0.20
0.375 0.125
45
1.55 0.20
0.175 0.075
4 4
0.235 0.045 0.825 0.445
0.42 0.09 x 8
1.27 BSC
All dimensions in millimeters.
1. XYY = assembly and date code. 2. Sample stock is generally held on all part numbers listed in BOLD. 4601.2006.05.1.3
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1.8A Current Limited P-Channel Switch
TSSOP-8
AAT4601
4.40 0.10
6.40 0.20
3.00 0.10 0.65 BSC
12 REF x 4
1.05 MAX
1.20 MAX
0.145 0.055 4 4
0.245 0.055 x 8
0.10 0.05 12
0.60 0.15 1.00 REF
DETAIL A
All dimensions in millimeters.
14
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1.8A Current Limited P-Channel Switch
MSOP-8
4 4 1.95 BSC
AAT4601
3.00 0.10
4.90 0.10
0.60 0.20 PIN 1 0.254 BSC
0.95 REF
3.00 0.10 10 5
0.95 0.15 0.85 0.10
0.075 0.075 0.65 BSC 0.30 0.08
All dimensions in millimeters.
GAUGE PLANE
0.155 0.075
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1.8A Current Limited P-Channel Switch
AAT4601
(c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 16
4601.2006.05.1.3

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