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Current Limited Load Switch General Description
The AAT4618 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 operating with inputs ranging from 2.4V to 5.5V which makes it ideal for 2.5V, 3V and 5V systems. An integrated current-limiting circuit protects the input supply from large currents which potentially cause the supply to fall out of regulation. In addition, the AAT4618 thermal overload protection limits power dissipation and junction temperatures associated with prolonged periods of operation in current limit. Due to its low RDS(ON), the AAT4618 can be used to control loads that require up to factory preset 400mA, 500mA, or 1A. The ultra fast current-limit response to a sudden short circuit is a mere 400ns which reduces the requirements of local supply bypassing. An open drain FAULT flag signals an over current or over temperature condition after a 4ms timeout. Quiescent current is a low 10A and in shutdown mode, the supply current decreases to less than 1A. The AAT4618 is available in a 5 pin SOT-23, and an 8 pin SC70JW specified over a -40 to 85C temperature range. The AAT4600 Series is a family of adjustable and fixed SmartSwitchTM products with a range of current handling capabilities. Available are single versions with adjustable current limit (AAT4610, AAT4601) as well as fixed current limit (AAT4625), and dual versions with fixed current limit (AAT4626, AAT4670).
AAT4618
Features
* *
SmartSwitchTM
* * * * * * * * * *
2.4V to 5.5V Input voltage range Current limit trip threshold options: * 400mA min * 500mA min * 1A min Fast transient response: * 400ns response to short circuit Low quiescent current * 10A typical * < 1A with Switch off 125m typical RDS(ON) FAULT flag with 4ms blanking Undervoltage Lockout Thermal shutdown Temp range -40 to 85C 4kV ESD Rating 5 pin SOT23 package 8 pin SC70JW package
Applications
* * * * * Peripheral ports USB Ports Notebook computers Personal communication devices Hot swap supplies
Typical Application
INPUT IN OUTPUT OUT
AAT4618
FAULT CIN 1F ON (ON) ON (ON) GND
100k FAULT COUT 0.47F
GND
GND
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Current Limited Load Switch Pin Descriptions
Pin #
SOT23-5 SC70JW-8
AAT4618
Symbol
OUT GND FAULT ON (ON) IN
Function
P-channel MOSFET drain Ground connection Open-drain FAULT output Enable Input: 4618 active low, 4618-1 active high P-channel MOSFET source
1 2 3 4 5
5 6, 7, 8 1 2 3, 4
Pin Configuration
SOT23-5 SC70JW-8
OUT GND FAULT
1 2 3
5
IN ON (ON)
4
FAULT ON (ON) IN IN
1 2
8 7
3 4
6 5
GND GND GND OUT
1 2
2
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Current Limited Load Switch Absolute Maximum Ratings
Symbol
VIN, FAULT VON VOUT IOUT TJ VESD TLEAD
AAT4618
(TA=25C unless otherwise noted) Value
-0.3 to 6 -0.3 to VIN+1 -0.3 to VIN+0.3 Internally Limited -40 to 150 4000 300
Description
IN, FAULT to GND ON (ON) to GND OUT to GND Output Current Operating Junction Temperature Range ESD Rating1--HBM Maximum Soldering Temperature (at Leads)
Units
V V V A C V C
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
Maximum Thermal Resistance 2 (SOT23-5, SC70JW-8) Maximum Power Dissipation 2 (SOT23-5, SC70JW-8)
Value
150 667
Units
C/W mW
Note 2: Mounted on a demo board.
(VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values are at TA=25C; bold values denote full temperature range) Symbol
VIN IQ IQ(OFF) ISD(OFF) VUVLO VUVLO(hys) RDS(ON) TCRDS ILIM VON(L) VON(H) ION(SINK) tRESP TOFF TON VFAULTLOW ISINK Tblank TSD
Electrical Characteristics
Description
Conditions
VIN = 5V, ON (ON) = active, IOUT = 0 ON (ON) = inactive, VIN = 5.5V ON (ON) = inactive, VIN = 5.5V, VOUT = 0 VIN falling VIN = 5.0V, TA = 25C VIN = 3.0V, TA = 25C AAT4618-0.4 AAT4618-0.5 AAT4618-1.0
Min
2.4
Typ
10
Max
5.5 25 1 1
Units
V A A A V V m ppm/C
Operation Voltage Quiescent Current Off Supply Current Off Switch Current Undervoltage Lockout Undervoltage Lockout Hysteresis On-Resistance ON-Resistance Temp-co Current Limit ON (ON) Input Low Voltage ON (ON) Input High Voltage ON (ON) Input leakage Current Loop Response Turn-Off Time Turn-On Time FAULT Logic Output Low FAULT Logic Output High Leakage Current Fault Blanking Time Over-temperature threshold
VOUT = VIN - 0.5V VIN = 2.7V to 5.5V 3 VIN = 2.7V to 4.2V 3 VIN = > 4.2V to 5.0V 3 VON (ON) = 5.5V VIN = 5V VIN = 5V, RL = 20 VIN = 5V, RL = 20 ISINK = 1mA VFAULT = 5.5V
0.1 1.9 0.3 125 155 2800 400 500 500 750 1000 1500 2.0 2.4 0.01 400 5 1 0.5 4 125
175 225 600 1000 2000 0.8
mA V V V A ns s s V A ms C
1
0.4 1
VIN = 5V
Note 3: For VIN outside this range consult Typical ON (ON) Threshold curve. 4618.2004.05.1.0
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Current Limited Load Switch Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C) Quiescent Current vs. Temperature
20 20
AAT4618
Quiescent Current vs. Input Voltage
Quiescent Current (A)
Quiescent Current (A)
15
15
10
10
5
5
0 -40 -20 0 20 40 60 80 100 120
0 0 1 2 3 4 5 6
Temperature (C)
IN (V)
Normalized Current Limit vs. VOUT
Normalized Current Limit
1.2 1 220 200 180 160 140 120 100 80 60 40 20 0 -40 -20
RDS(ON) vs. Temperature
VIN=3V
RDS(ON) (m)
0.8 0.6 0.4 0.2 0 0 1 2 3 4 5
VIN=5V
0
20
40
60
80
100
120
VOUT (V)
Temperature (C)
Off-Supply Current vs. Temperature
Off-Supply Current (A)
1.00 1.00
Off-Switch Current vs. Temperature
0.10
Off-Switch Current (A)
-20 0 20 40 60 80 100 120
0.10
0.01
0.01
0.00 -40
0.00 -40 -20 0 20 40 60 80 100 120
Temperature (C)
Temperature (C)
4
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Current Limited Load Switch Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C) Turn-On RL=20, CL=0.47F
6 5 6 5
AAT4618
Turn-Off RL=20, CL=0.47F
Voltage (V)
Voltage (V)
4 3 2 1 0 -1 -0.5
ON
OUT
4 3 2 1 0 -1 -10
ON
OUT
0.0
0.5
1.0
1.5
2.0
0
10
20
30
40
50
Time (s)
Time (s)
Short Circuit through 0.3
6
Thermal Shutdown Response
12 10
Input and Output (V)
Input Voltage Output Current Output Voltage
5 4 3 2 1 0 -1 0
6 4 2 0 1 2 3 4 5
Output (A)
8
Output Voltage (5V/div)
Output Current (1A/div)
Time (s)
Time (50ms/div)
Fault Delay from Short Circuit
2.4
ON (ON) Threshold vs. VIN
ON (ON) Threshold (V)
Output Voltage (5V/div) Output Current (1A/div) FAULT (5V/div)
2.2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 2 2.5 3 3.5 4 4.5 5 5.5
VON(H)
VON(L)
Time (1ms/div)
VIN (V)
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Current Limited Load Switch Functional Block Diagram
AAT4618
IN
Over-Temp Protection
OUT
Under-Voltage Lockout
Current Limit
ON (ON)
4ms Delay
FAULT
GND
Functional Description
The AAT4618 is a single channel current limited load switch that protects against short circuits by current limiting to a preset level. A patented fast acting current limit loop limits the current in a fraction of a micro second and instantly resets to low impedance once the short circuit condition is removed. The AAT4618 is internally protected from thermal damage by an over temperature detection circuit. If the die temperature reaches the internal thermal limit, the power device is switched off until the die temperature cools to a level below the thermal limit threshold. The device will thermal cycle indefinitely until the over current condition is removed. The AAT4618 operates with
input voltages ranging from 2.4V to 5.5V which, along with its extremely low operating current, makes it ideal for battery-powered applications. In cases where the input voltage drops below 2.4V, the AAT4618 MOSFET is protected from entering the saturated region of operation by being automatically shut down by an under voltage lockout circuit. A current limit condition is reported by the open drain FAULT output. A four millisecond blanking interval prevents false reporting during the charging of a capacitive load, which typically occurs during device turn-on, but may also occur during a port hot plug-in event. The AAT4618 is ideally suited for protection of peripheral ports such as USB, RS232 and parallel ports.
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Current Limited Load Switch Applications Information
Input Capacitor
The input capacitor, CIN protects the power supply from current transients generated by the load attached to the AAT4618. When a short circuit is suddenly applied to the output of the AAT4618, a large current, limited only by the RDS(ON) of the MOSFET, will flow for less than 1s before the current limit circuitry activates. (See characteristic curve "Short Circuit Through 0.3.") In this event, a moderately sized CIN will dramatically reduce the voltage transient seen by the power supply and by other circuitry upstream from the AAT4618. The extremely fast short circuit response time of the AAT4618 reduces the size requirement of CIN. CIN should be located as close to the device VIN pin as practically possible. Ceramic, tantalum or aluminum electrolytic capacitors are appropriate for CIN. There is no specific capacitor ESR requirement for CIN. However, for higher current operation, ceramic capacitors are recommended for CIN due to their inherent capability over tantalum capacitors to withstand input current surges from low impedance sources such as batteries in portable devices. When switching the AAT4618 on into a capacitive load, the AAT4618 will charge the output capacitive load at a rate no greater than the current limit setting.
AAT4618
Attaching Loads
Capacitive loads attached to an enabled AAT4618 will charge at a rate no greater than the current limit setting.
FAULT Output
The FAULT flag is provided to alert the system if an AAT4618 load is not receiving sufficient voltage to operate properly. If current limit or over temperature circuits in any combination are active for more than approximately four milliseconds, the FAULT flag is pulled to ground through approximately 100. The filtering of voltage or current transients of less than four milliseconds prevents capacitive loads connected to the AAT4618 output from activating the FAULT flag when they are initially attached. Pull up resistances of 1k to 100k are recommended. Since FAULT is an open drain terminal, it may be pulled up to any unrelated voltage less than the maximum operating voltage of 5.5V, allowing for level shifting between circuits.
Thermal Considerations
Since the AAT4618 has internal current limit and over temperature protection, junction temperature is rarely a concern. However, if the application requires large currents in a hot environment, it is possible that temperature rather than current limit will be the dominant regulating condition. In these applications, the maximum current available without risk of an over temperature condition must be calculated. The maximum internal temperature while current limit is not active can be calculated using Equation 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 AAT4618 at high temperature. RJA is the thermal resistance between the AAT4618 die and the board onto which it is mounted. TA(MAX) is the maximum temperature that the PCB under the AAT4618 would be if the AAT4618 were not dissipating power. Equation 1 can be rearranged to solve for IMAX; Equation 2. IMAX= TSD(MIN) - TA(MAX) RDS(ON)(MAX) x RJA
Output Capacitor
In order to insure stability while current limit is active, a small capacitance of approximately 0.47F is required. No matter how large the output capacitor however, output current is limited to the value set by the AAT4618 current limiting circuitry, so very large output capacitors can be used. For example, USB ports are specified to have at least 120F of capacitance down stream from their controlling power switch. The current limiting circuit will allow an output capacitance of 1000F or more without disturbing the upstream power supply.
ON (Enable Input)
In many systems, power planes are controlled by integrated circuits which run at lower voltages than the power plane itself. The enable input (ON) of the AAT4618 has low and high threshold voltages that accommodate this condition. The threshold voltages are compatible with 5 volt TTL, and 2.5 volt to 5 volt CMOS systems.
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Current Limited Load Switch
TSD(MIN) is the minimum temperature required to activate the AAT4618 over temperature protection. With typical specification of 125C, 115C is a safe minimum value to use. For example, if an application is specified to operate in 50C environments, the PCB operates at temperatures as high as 85C. The application is sealed and its PCB is small, causing RJA to be approximately 150 C/W. Using Equation 2, IMAX= 115 - 85 = 950 mA 220m x 150
AAT4618
The AAT4618 is safe to operate at the minimum current limit level of 500mA at 85C.
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Current Limited Load Switch Ordering Information
Package SOT23-5 SOT23-5 SOT23-5 SOT23-5 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 Enable Active Low Active High Active Low Active High Active Low Active High Active Low Active High Active Low Active High Current Limit 0.5 0.5 1.0 1.0 0.4 0.4 0.5 0.5 1.0 1.0 AVXYY DWXYY EVXYY EIXYY Marking1 AVXYY DWXYY EVXYY EIXYY Part Number (Tape and Reel) AAT4618IGV-0.5-T1 AAT4618IGV-0.5-1-T1 AAT4618IGV-1.0-T1 AAT4618IGV-1.0-1-T1 AAT4618IJS-0.4-T1 AAT4618IJS-0.4-1-T1 AAT4618IJS-0.5-T1 AAT4618IJS-0.5-1-T1 AAT4618IJS-1.0-T1 AAT4618IJS-1.0-1-T1
AAT4618
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
Package Information
SOT23-5
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
SC70JW-8
0.50 BSC 0.50 BSC 0.50 BSC
AAT4618
1.75 0.10 0.225 0.075 2.00 0.20
2.20 0.20
0.048REF 0.15 0.05
0.85 0.15
1.10 MAX
0.100
7 3
0.45 0.10 2.10 0.30
4 4
All dimensions in millimeters.
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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