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Current Limited Load Switch in SOT-23 Package General Description
The AAT4608 SmartSwitchTM is a member of AnalogicTechTM's Application Specific Power MOSFETTM (ASPMTM) product family. It is a 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 currents which may cause the supply to fall out of regulation. The AAT4608 is also protected from thermal overload which limits power dissipation and junction temperatures. It can be used to control loads that require up to 1 A. Current limit threshold is programmed with a resistor from SET to ground. The quiescent supply current is typically a low 15A max. The AAT4608 is available in a 5 pin SOT-23 specified over -40 to 85C.
AAT4608
Features
* * * * * * * * * * *
SmartSwitchTM
2.7V to 5.5V Input voltage range Programmable over current threshold Fast transient response: <1s response to short circuit Low quiescent current * 15A typical * 1A max with Switch off 160m typical RDS(ON) Undervoltage Lockout Thermal shutdown Temp range -40 to 85C 4kV ESD Rating 5 pin SOT-23 package
Applications
* * * * Peripheral ports Notebook computers Personal communication devices Hot swap supplies
Typical Application
INPUT
5
IN
AAT4608
SOT-23
OUT
1
OUTPUT
SET GND 1F
2
3
RSET
0.47F
GND
GND
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Current Limited Load Switch in SOT-23 Package Pin Descriptions
Pin #
1 2 3 4 5
AAT4608
Symbol
OUT GND SET NC IN
Function
P-channel MOSFET drain. Connect 0.47F capacitor from OUT to GND. Ground connection Current-Limit Set Input. A resistor from SET to ground sets the current limit for the switch. No internal connection. P-channel MOSFET source. Connect 1F capacitor from IN to GND.
Pin Configuration
5-Pin SOT-23 (Top View) OUT GND SET
1 5
IN
2
3
4
N/C
2
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Current Limited Load Switch in SOT-23 Package Absolute Maximum Ratings
Symbol
VIN VSET, VOUT IMAX TJ TLEAD VESD
AAT4608
(TA=25C unless otherwise noted) Value
-0.3 to 6 -0.3 to VIN+0.3 2 -40 to 150 300 4000
Description
IN to GND SET, OUT to GND Maximum Continuous Switch Current Operating Junction Temperature Range Maximum Soldering Temperature (at Leads) ESD Rating1 - HBM
Units
V V A C C V
Note: 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. Note 1: Human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin.
Thermal Characteristics
Symbol
JA PD
Description
Thermal Resistance Power Dissipation2
2
Value
150 667
Units
C/W mW
Note 2: Mounted on a demo board.
Electrical Characteristics
are at TA=25C) Symbol
VIN IQ VUVLO RDS(ON) ILIM ILIM(MIN) TRESP
(VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values
Description
Operation Voltage Quiescent Current Undervoltage Lockout On-Resistance Current Limit Minimum Current Limit Current Limit Response Time
Conditions
VIN = 5V, IOUT = 0 Rising edge, 1% hysteresis, VIN=5.0V VIN=4.5V VIN=3.0V RSET = 6.8k VIN=5V
Min
2.7 2.0
Typ
15 2.3 160 165 195 1 150 0.8
Max
5.5 30 2.7 180 230 2.0
Units
V
A
V m m m A mA s
0.5
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Current Limited Load Switch in SOT-23 Package Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C)
Quiescent Current vs. Temperature
Quiescent Current (A)
25 20 15 10 5 0 -40 -20 0 20 40 60 80 100 120
AAT4608
Quiescent Current
40
Input ( A )
30
20
10
0 2.5 3 3.5 4 4.5 5 5.5
Temperature (C)
Input ( V )
Output Current vs VOUT
0.6
RDS(ON) vs. Temperature
250 200
Output Current ( A)
Input = 3 V Input = 5V
0.4
RDS(ON) (m)
150 100 50 0 -40 -20 0 20 40
RSET =16 k
0.2
0 0 1 2 3 4 5
60
80
100
Vout ( V )
Te mperature (C)
Short Circuit through 0.3
8 12 8
Short Circuit through 0.6
9
Input and Output (V)
Input and Output (V)
6
Input Voltage Output Current
8
6
Input Voltage
6
Output (A)
4
4
4
Output Current
3
2
0
2
0
Output Voltage
0 0 1 2 3 -4
Output Voltage
0 0 1 2 3 -3
Time (s)
Time (s)
4
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Output (A)
Current Limited Load Switch in SOT-23 Package
AAT4608
(Unless otherwise noted, VIN = 5V, TA = 25C)
RSET vs ILIM
100 10
RSET coefficent vs I LIM
R SET I LIM Product ( kV )
9 8 7 6 5
R SET (k )
10
1 0.1
1
10
0
0.5
1
1.5
2
I LIM (A)
I LIM (A)
Current Limit v. Temperature
6%
Current Limit (%)
4% 2% 0% -2% -4% -6% -50
RSET = 22.1k V IN -VOUT=0.5V
- 25
0
25
50
75
100
Temperature (C)
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Current Limited Load Switch in SOT-23 Package Functional Block Diagram
AAT4608
IN
OUT
Undervoltage Lockout
Over-Temp Protection
1.2V Reference
Current Limit
SET
RSET GND
6
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Current Limited Load Switch in SOT-23 Package Applications Information
Setting Current Limit
In most applications, the variation in ILIM must be taken into account when determining RSET. The ILIM variation is due to processing variations from part to part, as well as variations in the voltages at IN (pin 5) and OUT (pin 3), plus the operating temperature. See charts "Current Limit vs. Temperature", and "Output Current vs. VOUT". Together these three factors add up to a 25% tolerance (see ILIM specification in Electrical Characteristics section). In the figure below, a cold device with a statistically higher current limit, and a hot device with a statistically lower current limit, both with RSET equal to 10.5k are shown. While the chart, "RSET vs. ILIM" indicates an ILIM of 0.7A with an RSET of 10.5k, this figure shows that the actual current limit will be at least 0.525A, and no greater than 0.880A.
Current Limit Using 10.5 k
1.2
AAT4608
that is less than or equal to it. For greater precision, the value of RSET may also be calculated using the ILIM RSET product found in the chart "RSET coefficient vs. ILIM". The maximum current is derived by multiplying the typical current for the chosen RSET in the chart by 1.25. A few standard resistor values are listed in the table "Current Limit RSET Values".
Current Limit RSET Values
RSET (k) 40.2 30.9 24.9 22.1 19.6 17.8 16.2 14.7 13.0 10.5 8.87 7.50 6.81 6.04 5.49 4.99 4.64 Current Limit typ (mA) 200 250 300 350 400 450 500 550 600 700 800 900 1000 1100 1200 1300 1400 Device will not current limit below: (mA) 150 188 225 263 300 338 375 413 450 525 600 675 750 825 900 975 1050 Device always current limits below: (mA) 250 313 375 438 500 563 625 688 750 875 1000 1125 1250 1375 1500 1625 1750
1
0.88 A
Device with high current limit at -40C
0.8
I LIM (A)
0.6
0.4
0.525 A
Device with low current limit at 85C
0.2
0 0 1 2 3 4 5
VOUT (V )
To determine RSET, start with the maximum current drawn by the load, and multiply it by 1.33. (typical_ILIM = minimum_ILIM / 0.75) This is the typical current limit value. Next, refer to "RSET vs. ILIM" and find the RSET that corresponds to the typical current limit value. Choose the largest resistor available
Example: A USB port requires 0.5A. 0.5A multiplied by 1.33 is 0.665A. From the chart named "RSET vs. ILIM", RSET should be less than 11k. 10.5 k is a standard value that is a little less than 11k but very close. The chart reads approximately 0.700A as a typical ILIM value for 10.5k. Multiplying 0.700A by 0.75 and 1.25 shows that the AAT4608 will limit the load current to greater than 0.525A but less than 0.875A.
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Current Limited Load Switch in SOT-23 Package
Overload Operation
1 0.75 0.5
AAT4608
Output ( V )
0.25 0 5 4 3 2 1 0 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3
Output Current 1 load is turned on at time = 0 Output Voltage
Tim e ( s )
Operation in Current Limit
When a heavy load is applied to the output of the AAT4608, the load current is limited to the value of ILIM determined by RSET. See the figure "Overload Operation". Since the load is demanding more current than ILIM, the voltage at the output drops. This causes the AAT4608 to dissipate a larger than normal quantity of power, and its die temperature to increase. When the die temperature exceeds an over temperature limit, the AAT4608 will shut down until is has cooled sufficiently, at which point it will startup again. The AAT4608 will continue to cycle on and off until the load is removed or power is removed.
Reverse Voltage
The AAT4608 is designed to control current flowing from IN to OUT. If a voltage is applied to OUT which is greater than the voltage on IN, large currents may flow. This could cause damage to the AAT4608.
8
Output (A)
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Current Limited Load Switch in SOT-23 Package Ordering Information
Package SOT-23-5 Marking1 CMXYY Part Number (Tape and Reel) AAT4608IGV-T1
AAT4608
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
Package Information
SOT-23-5
2.85 0.15 1.90 BSC 0.95 BSC
1.575 0.125
1.10 0.20
0.60 REF
2.80 0.20
1.20 0.25
0.15 0.07 4 4
GAUGE PLANE
10 5
0.40 0.10
0.075 0.075
0.60 REF
0.45 0.15
0.10 BSC
All dimensions in millimeters.
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Current Limited Load Switch in SOT-23 Package
AAT4608
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, and advise customers 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 10
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