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AAT4682
Dual Electronic Resettable Switches General Description
The AAT4682 Dual Electronic Resettable fuse is part of the AnalogicTech Application Specific Power MOSFET (ASPMTM) line of products. It has two 1A current limited P-channel MOSFET power devices that remain fully enhanced as long as the input power supply is above an under voltage lockout threshold, and the load is below the current limit setting. If the load increases above the current limit setting, as is the case during a short circuit, the MOSFET effectively becomes a constant current source equal to the current limit. If the current limit condition persists long enough to heat the MOSFET to an extreme temperature, both devices will thermal cycle off and on until the current limit condition is removed. Independent open drain FAULT flags signal an over current or over temperature condition. Quiescent current typically is a low 10A. The AAT4682 is available in a 6 pin SOT-23, specified over a -40 to 85C temperature range.
Features
* * * * * * * * * * *
SmartSwitchTM
Dual P-Channel MOSFETS 500mA steady state load current 600mA minimum current limit trip point Low quiescent current, typically 10A. Over temperature protection Fast transient response: * < 1s response to short circuit 400m typical RDS(ON) Undervoltage Lockout Temp range -40 to 85C FAULT flag with 2ms blanking 6-pin SOT23 package
Preliminary Information
Applications
* * * * USB ports Peripheral ports Desktop PCs Cell phone ports
Typical Application
AAT4682
INPUT
5
IN
OUTA OUTB FAULTA GND
2
6 4 1 3
OUTA OUTB FAULTA FAULTB
FAULTB
CIN 1F GND
COUTA 1F
COUTB 1F
GND
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AAT4682
Dual Electronic Resettable Switches Pin Descriptions
Pin #
1 2 3 4 5 6
Symbol
FAULTA GND FAULTB OUTB IN OUTA
Function
Channel A open drain output signals over-current and over-temperature condition Ground connection Channel B open drain output signals over-current and over-temperature condition Channel B P-channel MOSFET drain Channel A and Channel B P-channel MOSFET sources Channel A P-channel MOSFET drain
Pin Configuration
SOT23-6
FAULTA GND FAULTB
16 25 34
OUTA IN OUTB
2
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AAT4682
Dual Electronic Resettable Switches Absolute Maximum Ratings
Symbol
VIN VOUT VFLG IOUT TJ VESD TLEAD
(TA=25C unless otherwise noted) Value
-0.3 to 6 -0.3 to 6 -0.3 to 6 Internally Limited -40 to 150 5000 300
Description
IN to GND OUTA or OUTB to GND FAULTA or FAULTB 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 Maximum Power Dissipation2
2
Value
150 667
Units
C/W mW
Note 2: Mounted on a demo board.
Electrical Characteristics
Symbol
VIN IQ VUVLO VUVLO(hys) RDS(ON) ILIM tRESP VFAULTLOW ISINK Tblank TSD
(VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values
are at TA=25C; bold values designate full temperature range) Description
Operation Voltage Quiescent Current Undervoltage Lockout Undervoltage Lockout Hysteresis On-Resistance Current Limit Current Loop Response FAULT Logic Output Low FAULT Logic Output High Leakage Current FAULT Blanking Time Over-temperature threshold
Conditions
VIN = 5V, IOUT = 0 VIN falling VIN = 5.0V,TA = 25C VIN = 3.V,TA = 25C OUT < IN - 0.5V VIN = 5V ISINK = 1mA VFAULT = 5.5V
Min
1.8
Typ
10 1.5 0.3 400 525 0.875 500 0.5 2 125
Max
5.5 20
Units
V A V V m A ns V A ms C
0.6
500 650 1.25 0.4 1
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AAT4682
Dual Electronic Resettable Switches Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C) Quiescent Current vs. Temperature
20
Quiescent Current vs. Input Voltage
Quiescent Current (A)
12 10 8 6 4 2 0 0 1 2 3 4 5 6
Quiescent Current (A)
18 16 14 12 10 8 6 4 2 0 -40 -20 0 20 40 60 80 100 120
Input (V)
Temperature (C)
Current Limit vs. Output Voltage
1.0 600 0.8
RDS(ON) vs. Temperature
Output (A)
550
RDS(ON) (m)
0.6 0.4 0.2 0.0 0 1 2 3 4 5
VIN=3V
500 450 400
VIN=5V
350 300 -40
Output (V)
-20
0
20
40
60
80
100
120
Temperature (C)
Short Circuit Through 0.3
6 7 6
Short Circuit Through 0.6
5
Input and Output (V)
4
Input Voltage
5
Input and Output (V)
Input Voltage Output (A)
4 3
2
3
Output (A)
Output Voltage
0 1
Output Current
2 1
Output Voltage
0 -0.5 -1 0.0 0.5 1.0 1.5 2.0
Output Current
-2 -0.5 -1 0.0 0.5 1.0 1.5 2.0
Time (s)
Time (s)
4
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AAT4682
Dual Electronic Resettable Switches Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C)
Thermal Shutdown Response
FAULTA (5V/div) OUTA (5V/div)
Fault Delay
FAULTA (5V/div) OUTA (5V/div)
FAULTB (5V/div) OUTB (5V/div) IIN (1A/div)
FAULTB (5V/div) OUTB (5V/div) IIN (1A/div)
50ms/div
500s/div
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AAT4682
Dual Electronic Resettable Switches Functional Block Diagram
INA
OUTB
ILIM
UVLO OTMP
ILIM
OUTB FAULTA
3ms Blanking
FAULTB
3ms Blanking
GND
Functional Description
The AAT4682 is a dual channel electronic resettable fuse that protects against short circuit conditions by current limiting to a preset level. A patented fast acting current limit loop limits load current in a fraction of a microsecond, and instantly resets back to a low impedance state once the short circuit condition is removed. A current limit condition is reported by the open drain FAULT output after a two millisecond blanking interval. The blanking prevents false reporting during the charging of a capacitive load, which typically occurs when a load is connected. The AAT4682 is internally protected from thermal damage by an over temperature detection circuit. If the die temperature reaches the internal thermal limit, both power devices are 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. Due to the high thermal conductivity of silicon and the size of the die, the temperature across the die is relatively uniform at high temperatures, and therefore, as a precaution, both power devices are switched off when the thermal threshold is reached. The AAT4682 operates with input voltages ranging from 1.8V 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 1.8V, the AAT4682 internal MOSFETS are protected from entering the saturated region of operation by being automatically shut down by an undervoltage lockout circuit. The AAT4682 is ideally suited for protection of peripheral ports such as USB, RS232 and parallel ports.
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AAT4682
Dual Electronic Resettable Switches Applications Information
Input Capacitor
The input capacitor protects the power supply from current transients generated by the loads attached to the AAT4682. If a short circuit is suddenly applied to a AAT4682 output, there is a 500 nanosecond long period during which a large current can flow before current limit circuitry activates. (See characteristic curve "Short Circuit Through 0.3.") In this event, a properly sized input capacitor can dramatically reduce the voltage transient seen by the power supply and other circuitry upstream from the AAT4682. CIN should be located as close to the device VIN pin as practically possible. Ceramic, tantalum or aluminum electrolytic capacitors may be selected 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. tive loads connected to the AAT4682 output from activating the FAULT flag when they are initially attached. Pull up resistances of 10k to 100k are recommended. Since the FAULT outputs are open drain terminals, they may be pulled up to any voltage rail less than the maximum operating voltage of 5.5V, allowing for level shifting between circuits.
Thermal Considerations
Since the AAT4682 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 combined current available without risk of an over temperature condition can be calculated. The maximum internal temperature while current limit is not active can be calculated using Equation 1. TJ(MAX) = IMAX2 x R DS(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 AAT4682 at high temperature. RJA is the thermal resistance between the AAT4682 die and the board onto which it is mounted. TA(MAX) is the maximum temperature that the PCB under the AAT4682 would be if the AAT4682 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 Capacitors
In order to insure stability while current limit is active, a small output capacitance of approximately 1F is required at each output. No matter how big the output capacitor, output current is limited to the value set by the AAT4682 current limiting circuitry, allowing very large output capacitors to 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.
Attaching Loads
Capacitive loads attached to the AAT4682 will charge at a rate no greater than the current limit setting.
TSD(MIN) is the minimum temperature required to activate the AAT4682 over temperature protection. The typical over temperature threshold specification is 125C, therefore 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 150C/W. Using Equation 2, IMAX= 115 - 85 = 575mA 600 x 150
FAULT Outputs
FAULT flags are provided to alert a system if a AAT4682 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 two milliseconds, the corresponding FAULT output is pulled to ground through approximately 100. Removal of voltage or current transients of less than two milliseconds prevents capaci-
To prevent thermal limiting, the combined operating load current of each output in the application must be less than 575mA.
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AAT4682
Dual Electronic Resettable Switches Ordering Information
Part Number Package SOT23-6 Marking Bulk N/A Tape and Reel AAT4682IGU-T1
Package Information
e1 e t
Dim A A1 A2 b c D E E1 e e1 f L L1 L2 t
L2
E
L
f D
GAUGE PLANE
C
Millimeters Min Max 0.95 1.45 0.05 0.15 0.90 1.30 0.35 0.50 0.08 0.20 2.84 3.00 1.50 1.70 2.60 3.00 0.95 BSC 1.90 BSC 0.50 BSC 0.23 0.40 0.10 BSC 0.60 BSC 0 10
Inches Min Max 0.037 0.057 0.002 0.006 0.035 0.051 0.0137 0.019 0.0031 0.0078 0.1118 0.118 0.059 0.0669 0.102 0.118 0.0374 BSC 0.0748 BSC 0.0197 BSC 0.009 0.016 0.039 BSC 0.0236 BSC 0 10
A2
A
b A1
Advanced Analogic Technologies, Inc.
1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086 Phone (408) 524-9684 Fax (408) 524-9689 8
4682.2001.11.0.9

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