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| AAT4618 Current Limited Load Switch General Description The AAT4618 SmartSwitchTM is a member of AnalogicTech'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 500mA even while operating at high ambient temperatures. 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). Features * * * * SmartSwitchTM * * * * * * * * 2.4V to 5.5V Input voltage range 500mA min current limit trip threshold Fast transient response: * 400ns response to short circuit Low quiescent current * 10A typical * < 1A with Switch off 125m typical R DS(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 Preliminary Information Applications * * * * * Peripheral ports USB Ports Notebook computers Personal communication devices Hot swap supplies Typical Application INPUT IN OUT OUTPUT AAT4618 100k FAULT CIN 1F ON (ON) ON (ON) GND COUT 0.47F FAULT GND GND 4618.2002.2.0.9 1 AAT4618 Current Limited Load Switch Pin Descriptions Pin # SOT23-5 SC70JW-8 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 4618.2002.2.0.9 AAT4618 Current Limited Load Switch Absolute Maximum Ratings Symbol VIN, FAULT VON VOUT IOUT TJ VESD TLEAD (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 Maximum Power Dissipation 2 2 Value 150 667 Units C/W mW Note 2: Mounted on a demo board. Electrical Characteristics 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 (VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values are at TA=25C; bold values denote full temperature range) Description 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 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 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 Min 2.4 Typ 10 0.1 1.9 0.3 125 155 2800 750 Max 5.5 20 1 1 Units V A A A V V m ppm/C mA V V V A ns s s V A ms C 175 225 1000 0.8 500 2.0 2.4 0.01 400 5 1 0.5 4 125 1 0.4 1 VIN = 5V Note 3: For VIN outside this range consult Typical ON (ON) Threshold curve. 4618.2002.2.0.9 3 AAT4618 Current Limited Load Switch Typical Characteristics (Unless otherwise noted, VIN = 5V, TA = 25C) Quiescent Current vs. Temperature 20 20 Quiescent Current vs. Input Voltage Quiescent Current (A) 15 Quiescent Current (A) 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) Current Limit vs. VOUT 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 1 2 3 4 5 220 200 180 160 140 120 100 80 60 40 20 0 -40 -20 RDS(ON) vs. Temperature Current Limit (A) VIN=3V RDS(ON) (m) VIN=5V VOUT (V) 0 20 40 60 80 100 120 Temperature (C) Off-Supply Current vs. Temperature Off-Supply Current (A) 1.00 1.00 Off-Switch Current vs. Temperature Off-Switch Current (A) -20 0 20 40 60 80 100 120 0.10 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 4618.2002.2.0.9 AAT4618 Current Limited Load Switch Typical Characteristics (Unless otherwise noted, VIN = 5V, TA = 25C) Turn-On RL=20, CL=0.47F 6 5 6 5 Turn-Off RL=20, CL=0.47F Voltage (V) Voltage (V) 4 3 2 1 0 -1 -0.5 0.0 0.5 1.0 1.5 2.0 4 3 2 1 0 -1 -10 ON OUT ON OUT 0 10 20 30 40 50 Time (s) Time (s) Short Circuit through 0.3 6 12 Thermal Shutdown Response Input and Output (V) Input Voltage 5 10 Output Current 4 3 2 1 0 -1 0 1 2 3 4 5 Output Voltage 8 6 4 2 0 Output (A) 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) 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 Output Voltage (5V/div) Output Current (1A/div) FAULT (5V/div) VON(H) VON(L) Time (1ms/div) VIN (V) 4618.2002.2.0.9 5 AAT4618 Current Limited Load Switch Functional Block Diagram IN OUT Under-Voltage Lockout Over-Temp Protection 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. 6 4618.2002.2.0.9 AAT4618 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. 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. 4618.2002.2.0.9 7 AAT4618 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 The AAT4618 is safe to operate at the minimum current limit level of 500mA at 85C. 8 4618.2002.2.0.9 AAT4618 Current Limited Load Switch Ordering Information Part Number Package SOT23-5 SOT23-5 SC70JW-8 SC70JW-8 Enable Active Low Active High Active Low Active High Marking Bulk N/A N/A N/A N/A Tape and Reel AAT4618IGV-T1 AAT4618IGV-1-T1 AAT4618IJS-T1 AAT4618IJS-1-T1 Package Information SOT23-5 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 4618.2002.2.0.9 9 AAT4618 Current Limited Load Switch SC70JW-8 e e e Dim E E1 L A A1 A2 D e b c 1 E b D 0.048REF c A2 A Millimeters Min Max 2.10 BSC 1.75 2.00 0.23 0.40 1.10 0 0.10 0.70 1.00 2.00 BSC 0.50 BSC 0.15 0.30 0.10 0.20 0 8 4 10 Inches Min Max 0.083 BSC 0.069 0.079 0.009 0.016 0.043 0.004 0.028 0.039 0.079 BSC 0.020 BSC 0.006 0.012 0.004 0.008 0 8 4 10 A1 1 L E1 Advanced Analogic Technologies, Inc. 1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086 Phone (408) 524-9684 Fax (408) 524-9689 10 4618.2002.2.0.9 |
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