AAT4612

Current Limited Load Switch General Description The AAT4612 SmartSwitch is a current limited Pchannel MOSFET power switch designed for highside load switching applications operating with inputs ranging from 2.4V to 5.5V, making it ideal for both 3V and 5V systems. An integrated current limiting circuit protects the input supply from large currents which could potentially cause the supply to fall out of regulation. In addition, the AAT4612’s 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 AAT4612 can be used to control loads that require up to 1A even while operating at high ambient temperatures. The ultra-fast current limit response to a sudden short circuit is a mere 500ns which reduces the requirements of local supply bypassing. Quiescent current is a low 10µA and, in shutdown mode, the supply current decreases to less than 1µA. The AAT4612 is available in a Pb-free 5-pin SOT23 package or a Pb-free 8-pin SC70JW package and is specified over the -40°C to +85°C temperature range. AAT4612 Features • • • • • • • • • • SmartSwitch™ Input Voltage Range: 2.4V to 5.5V 1A Current Limit Trip Threshold Fast Transient Response: • 4.2V to 5.0V1 VON = 5.5V VIN = 5V VIN = 5V, RL = 10Ω VIN = 5V, RL = 10Ω Min 2.4 Typ 10 0.1 1.9 0.3 130 170 1.5 Max 5.5 20 1 1 Units V µA µA µA V V mΩ A V V 1 2.0 2.4 175 225 2.0 0.8 0.01 500 2.5 1 125 1 µA ns µs µs °C 1. For VIN outside this range, consult typical ON threshold curve. 4 4612.2006.09.1.3 Current Limited Load Switch Typical Characteristics Quiescent Current vs. Temperature 20 20 AAT4612 Quiescent Current vs. Input Voltage Quiescent Current (µA) 15 Quiescent Current (µA) -40 -20 0 20 40 60 80 100 120 15 10 10 5 5 0 0 0 1 2 3 4 5 6 Temperature (°C) Input Voltage (V) Current Limit vs. Output Voltage 1.4 1.2 250 RDS(ON) vs. Temperature VIN = 3V 200 Current Limit (A) RDS(ON) (mΩ) 1.0 0.8 0.6 0.4 0.2 0.0 0 1 2 3 4 5 150 VIN = 5V 100 50 0 -40 -20 0 20 40 60 80 100 120 Output Voltage (V) Temperature (°C) Off-Supply Current vs. Temperature Off-Supply Current (µA) 1.00 1.00 Off-Switch Current vs. Temperature Off-Switch Current (µA) 0.10 0.10 0.01 0.01 0.00 -40 -20 0 20 40 60 80 100 120 0.00 -40 -20 0 20 40 60 80 100 120 Temperature (°C) Temperature (°C) 4612.2006.09.1.3 5 Current Limited Load Switch Typical Characteristics Turn-On Turn-Off AAT4612 (RL = 10Ω; CL = 0.47µF) 6 5 6 5 (RL = 10Ω; CL = 0.47µF) Voltage (V) 3 2 1 0 -1 -0.5 ON OUT Voltage (V) 4 4 3 2 1 0 -1 ON OUT 0.0 0.5 1.0 1.5 2.0 -5 0 5 10 15 20 Time (µs) Time (µs) Short Circuit Through 0.3Ω Input and Output Voltage (V) 6.0 12 Thermal Shutdown Response Input Voltage 5.0 4.0 3.0 2.0 1.0 0.0 -1 0 1 2 3 4 5 10 8 6 Output Current (A) Output Voltage (5V/div) Output Current Output Voltage 4 2 0 Output Current (1A/div) Time (50ms/div) Time (µs) ON Threshold vs. Input Voltage 2.4 2.2 ON Threshold (V) 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 2 2.5 3 VON(H) VON(L) 3.5 4 4.5 5 5.5 Input Voltage (V) 6 4612.2006.09.1.3 Current Limited Load Switch Functional Block Diagram AAT4612 IN OverTemperature Protection OUT Under-Voltage Lockout Current Limit ON GND Functional Description The AAT4612 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 microsecond and instantly resets to low impedance once the short-circuit condition is removed. The AAT4612 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 ther- mal limit threshold. The device will thermal cycle indefinitely until the over-current condition is removed. The AAT4612 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 AAT4612 MOSFET is protected from entering the saturated region of operation by being automatically shut down by an under-voltage lockout circuit. The AAT4612 is ideally suited for protection of peripheral ports such as USB, RS232, and parallel ports. 4612.2006.09.1.3 7 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 AAT4612. When a short circuit is suddenly applied to the output of the AAT4612, a large current, limited only by the RDS(ON) of the MOSFET, will flow for less than 1µs before the current limit circuitry activates. (See characteristic curve "Short Circuit Through 0.3Ω.") 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 AAT4612. The extremely fast short-circuit response time of the AAT4612 reduces the size requirement of CIN. CIN should be located as close to the device IN 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. that accommodate this condition. The threshold voltages are compatible with 5V TTL and 2.5V to 5V CMOS systems. When switching the AAT4612 on into a capacitive load, the AAT4612 will charge the output capacitive load at a rate no greater than the current limit setting. AAT4612 Attaching Loads Capacitive loads attached to an enabled AAT4612 will charge at a rate no greater than the current limit setting. Thermal Considerations Since the AAT4612 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. Output Capacitor In order to insure stability while current limit is active, a small capacitance of approximately 0.47µF is required. No matter how large the output capacitor, however, output current is limited to the value set by the AAT4612 current limiting circuitry, so very large output capacitors can be used. For example, USB ports are specified to have at least 120µF of capacitance downstream from their controlling power switch. The current limiting circuit will allow an output capacitance of 1000µF or more without disturbing the upstream power supply. Eq. 1: TJ(MAX) = IMAX2 · RDS(ON)(MAX) · RΘJA + 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 AAT4612 at high temperature. RθJA is the thermal resistance between the AAT4612 die and the board onto which it is mounted. TA(MAX) is the maximum temperature that the PCB under the AAT4612 would be if the AAT4612 were not dissipating power. Equation 1 can be rearranged to solve for IMAX: ON 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 AAT4612 has low and high threshold voltages Eq. 2: IMAX = TSD(MIN) - TA(MAX) RDS(ON)(MAX) · RΘJA TSD(MIN) is the minimum temperature required to activate the AAT4612 over-temperature protection. 8 4612.2006.09.1.3 Current Limited Load Switch With typical specification of 125°C, 115°C is a safe minimum value to use. For example, if an application is specified to operate in 50°C environments, the PCB operates at temperatures as high as 85°C. The application is sealed and its PCB is small, causing RθJA to be approximately 150°C/W. Using Equation 2, AAT4612 Eq. 3: IMAX = TSD(MIN) - TA(MAX) RDS(ON)(MAX) · RΘJA The AAT4612 is safe to operate at the maximum current level of 0.93A at 85°C. 4612.2006.09.1.3 9 Current Limited Load Switch Ordering Information Package SOT23-5 SC70JW-8 AAT4612 Marking1 ATXYY ATXYY Part Number (Tape and Reel)2 AAT4612IGV-T1 AAT4612IJS-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 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. 1. XYY = assembly and date code. 2. Sample stock is generally held on all part numbers listed in BOLD. 10 4612.2006.09.1.3 Current Limited Load Switch SC70JW-8 0.50 BSC 0.50 BSC 0.50 BSC AAT4612 1.75 ± 0.10 0.225 ± 0.075 2.00 ± 0.20 2.20 ± 0.20 0.048REF 0.85 ± 0.15 1.10 MAX 0.15 ± 0.05 0.100 7 ° ± 3° 0.45 ± 0.10 2.10 ± 0.30 4° ± 4° All dimensions in millimeters. © 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 4612.2006.09.1.3 0.05 ± 0.05 11