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| Dual Electronic Resettable Switch General Description The AAT4682 dual electronic resettable fuse is a member of AnalogicTech's Application Specific Power MOSFETTM (ASPMTM) product family. 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 Pb-free, 6-pin SOT23 package and is specified over the -40C to +85C temperature range. AAT4682 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) Under-Voltage Lockout Temperature Range: -40C to +85C FAULT Flag with 2ms Blanking 6-Pin SOT23 Package Applications * * * * Cell Phone Ports Desktop PCs Peripheral Ports USB Ports Typical Application AAT4682 IN OUTA OUTB FAULTA GND FAULTB INPUT 5 6 4 1 3 OUTA OUTB FAULTA FAULTB CIN 1F GND 2 COUTA 1F COUTB 1F GND 4682.2006.05.1.2 1 Dual Electronic Resettable Switch Pin Descriptions Pin # 1 2 3 4 5 6 AAT4682 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 4682.2006.05.1.2 Dual Electronic Resettable Switch Absolute Maximum Ratings1 TA = 25C, unless otherwise noted. Symbol VIN VOUT VFLG IOUT TJ VESD TLEAD AAT4682 Description IN to GND OUTA or OUTB to GND FAULTA or FAULTB to GND Output Current Operating Junction Temperature Range ESD Rating2 - HBM Maximum Soldering Temperature (at Leads) Value -0.3 to 6 -0.3 to 6 -0.3 to 6 Internally Limited -40 to 150 5000 300 Units V V V A C V C Thermal Characteristics3 Symbol JA PD Description Maximum Thermal Resistance Maximum Power Dissipation Value 150 667 Units C/W mW 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 a demo board. 4682.2006.05.1.2 3 Dual Electronic Resettable Switch Electrical Characteristics VIN = 5V, TA = -40C 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 AAT4682 Description Operation Voltage Quiescent Current Under-Voltage Lockout Under-Voltage 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 to 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 4 4682.2006.05.1.2 Dual Electronic Resettable Switch Typical Characteristics Unless otherwise noted, VIN = 5V, TA = 25C. AAT4682 Quiescent Current vs. Temperature Quiescent Current (A) 18 16 14 12 10 8 6 4 2 0 -40 -20 0 20 40 60 80 100 120 Quiescent Current vs. Input Voltage Quiescent Current (A) 12 10 8 6 4 2 0 0 1 2 3 4 5 6 20 Temperature (C) Input Voltage (V) Current Limit vs. Output Voltage 1.0 600 550 RDS(ON) vs. Temperature Output Current (A) 0.8 RDS(ON) (m) VIN = 3V 500 450 400 0.6 0.4 0.2 VIN = 5V 350 300 -40 0.0 0 1 2 3 4 5 -20 0 20 40 60 80 100 120 Output Voltage (V) Temperature (C) Short Circuit Through 0.3 Input and Output Voltage (V) 6 7 Short Circuit Through 0.6 Input and Output Voltage (V) 6 Input Voltage 5 Output Current (A) Output Current (A) 4 Input Voltage 5 4 3 2 3 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) 4682.2006.05.1.2 5 Dual Electronic Resettable Switch Typical Characteristics Unless otherwise noted, VIN = 5V, TA = 25C. Thermal Shutdown Response FAULTA (5V/div) OUTA (5V/div) FAULTB (5V/div) OUTB (5V/div) IIN (1A/div) AAT4682 Fault Delay FAULTA (5V/div) OUTA (5V/div) FAULTB (5V/div) OUTB (5V/div) IIN (1A/div) Time (50ms/div) Time (500s/div) 6 4682.2006.05.1.2 Dual Electronic Resettable Switch Functional Block Diagram AAT4682 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; 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 under-voltage lockout circuit. The AAT4682 is ideally suited for protection of peripheral ports such as USB, RS232, and parallel ports. 4682.2006.05.1.2 7 Dual Electronic Resettable Switch 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 equivalent series resistance (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. AAT4682 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 capacitive 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. Eq. 1: TJ(MAX) = IMAX2 * RDS(ON)(MAX) * RJA + TA(MAX) 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 downstream 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. 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. Eq. 2: IMAX = TSD(MIN) - TA(MAX) RDS(ON)(MAX) * RJA 8 4682.2006.05.1.2 Dual Electronic Resettable Switch 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: AAT4682 Eq. 3: IMAX = 115 - 85 600 * 150 = 575mA To prevent thermal limiting, the combined operating load current of each output in the application must be less than 575mA. 4682.2006.05.1.2 9 Dual Electronic Resettable Switch Ordering Information Package SOT23-6 AAT4682 Marking1 BXXYY Part Number (Tape and Reel)2 AAT4682IGU-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 2.85 0.15 1.90 BSC 0.95 BSC 1.575 0.125 1.10 0.20 2.80 0.20 1.20 0.25 0.075 0.075 0.15 0.07 GAUGE PLANE 10 5 0.40 0.10 x 6 4 4 0.60 REF 0.45 0.15 0.10 BSC All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. (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 10 4682.2006.05.1.2 |
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