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AAT4680
Electronic Resettable Fuse General Description
The AAT4680 Electronic Resettable Fuse is part of the AnalogicTech Application Specific Power MOSFET (ASPMTM) line of products. It is a 1A current limited P-channel MOSFET power device that remains 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, the device will thermal cycle off and on until the current limit condition is removed. An open drain FAULT flag signals an over current or over temperature condition. Quiescent current is typically a low 10A. The AAT4680 is available in a 5-pin SOT-23, specified over a -40 to 85C temperature range.
Features
* * * * * * * * * *
SmartSwitchTM
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 3ms blanking 5-pin SOT23 package
Preliminary Information
Applications
* * * * USB ports Peripheral ports Desktop PCs Cell phone ports
Typical Application
5
INPUT
IN
OUT
1
OUT FAULT COUT 1F
AAT4680
FAULT CIN 1F GND
2 3
GND
GND
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AAT4680
Electronic Resettable Fuse Pin Descriptions
Pin #
1 2 3 4 5
Symbol
OUT GND FAULT NC IN
Function
P-channel MOSFET drain Ground connection Open drain output signals over-current and over-temperature condition Not internally connected P-channel MOSFET source
Pin Configuration
SOT23-5
OUT GND FAULT
1 2 3
5
IN
4
NC
2
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AAT4680
Electronic Resettable Fuse 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 OUT to GND FAULT 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 Resistance2 Maximum Power Dissipation2
Value
150 667
Units
C/W mW
Note 2: Mounted on a demo board.
Electrical Characteristics (VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values are at TA=25C; bold values designate full temperature range)
Symbol
VIN IQ VUVLO VUVLO(hys) RDS(ON) ILIM tRESP VFAULTLOW ISINK Tblank TSD
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 3 125
Max
5.5 20 1.8 500 650 1.25 0.4 1
Units
V A V V m A ns V A ms C
0.6
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AAT4680
Electronic Resettable Fuse Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C) Quiescent Current vs. Temperature
20
12
Quiescent Current vs. Input Voltage
Quiescent Current (A)
Quiescent Current (A)
18 16 14 12 10 8 6 4 2 0 -40 -20 0 20 40 60 80 100 120
10 8 6 4 2 0 0 1 2 3 4 5 6
Temperature (C)
Input (V)
Current Limit vs. Output Voltage
700 1 650 0.8 600 550 500 450 400 350 0 1 2 3 4 5 300 -40
RDS(ON) vs. Temperature
0.6 0.4 0.2 0
RDS(ON) (m)
Output (A)
VIN=3V
VIN=5V
-20
0
20
40
60
80
100
120
Output (V)
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)
Output (A)
2
3
Output Voltage
0 1
Output Current
2 1
Output Current
-2 -0.5 -1 0.0 0.5 1.0 1.5 2.0
Output Voltage
0 -0.5 -1 0.0 0.5 1.0 1.5 2.0
Time (s)
Time (s)
4
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Output (A)
4
Input Voltage
3
AAT4680
Electronic Resettable Fuse Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C)
Thermal Shutdown Response
Fault Delay
FAULT (5V/div)
FAULT (5V/div)
VOUT (2V/div) VOUT (2V/div) IIN (500mA/div)
IIN (500mA/div)
50ms/div
2ms/div
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AAT4680
Electronic Resettable Fuse Functional Block Diagram
IN
Over-Temp Protection
OUT
Under-Voltage Lockout
Current Limit
FAULT
3ms Blanking
GND
Functional Description
The AAT4680 is a single 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 to low impedance once the short circuit condition is removed. A current limit condition is reported by the open drain FAULT output after a three millisecond blanking interval. The blanking prevents false reporting during the charging of a capacitive load, which typically occurs when a load is connected. The AAT4680 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 AAT4680 operates with input voltages ranging from 1.8V to 5.5V which, along with extremely low operating current, makes it ideal for battery-powered applications. In cases where the input voltage drops below 1.8V, the AAT4680 internal MOSFET is protected from entering the saturated region of operation by being automatically shut down by an under voltage lockout circuit. The AAT4680 is ideally suited for protection of peripheral ports such as USB, RS232 and parallel ports.
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AAT4680
Electronic Resettable Fuse Applications Information
Input Capacitor
The input capacitor, CIN, protects the power supply from current transients generated by the load attached to the AAT4680. If a short circuit is suddenly applied to the output of the AAT4680, 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 AAT4680. 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. than two milliseconds prevents capacitive loads connected to the AAT4680 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 voltage rail less than the maximum operating voltage of 5.5V, allowing for level shifting between circuits.
Thermal Considerations
Since the AAT4680 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 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 AAT4680 at high temperature. RJA is the thermal resistance between the AAT4680 die and the board onto which it is mounted. TA(MAX) is the maximum temperature that the PCB under the AAT4680 would be if the AAT4680 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 output capacitance of approximately 1F is required. No matter how big the output capacitor, output current is limited to the value set by the AAT4680 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 AAT4680 will charge at a rate no greater than the current limit setting.
TSD(MIN) is the minimum temperature required to activate the AAT4680 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 150C/W. Using Equation 2, IMAX= 115 - 85 = 575 mA 600 x 150
FAULT Output
A FAULT flag is provided to alert a system if the AAT4680 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 three milliseconds, FAULT is pulled to ground through approximately 100 . Removal of voltage or current transients of less
To prevent thermal limiting, the operating load current in the application must be less than 575mA.
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AAT4680
Electronic Resettable Fuse Ordering Information
Part Number Package SOT23-5 Marking Bulk N/A Tape and Reel AAT4680IGV-T1
Package Information
e
Dim
S1
E
H
D
A A1 S b
I
c L
A A1 A2 b c D E e H L S S1
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 1.90 2.60 3.00 0.35 0.55 0.47 0.55 .95 0 10
Inches Min Max 0.037 0.057 0.002 0.006 0.035 0.051 0.014 0.019 0.003 0.078 0.112 0.112 0.059 0.067 0.0748 0.102 0.118 .0137 .0216 0.019 .0216 0.037 0 10
Advanced Analogic Technologies, Inc.
1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086 Phone (408) 524-9684 Fax (408) 524-9689 8
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