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Dual-Input, Dual-Output Load Switches General Description
The AAT4670 SmartSwitchTM is part of AnalogicTechTM's Application Specific Power MOSFETTM (ASPMTM) line of products. The AAT4670 consists of dual, independent, 1A current limited, slew rate controlled P-channel MOSFET power switches with a dedicated source and drain pin assigned to each switch. The internal circuitry automatically derives power from the higher of the two input power source pins with a low operating quiescent current of 18A. In shutdown mode, the supply current decreases to less than 1A. The switches operate with inputs ranging from 2.2V to 5.5V, making them ideal for 2.5V, 3V and 5V systems. The dual configuration permits integration of the load switch function for systems with two different power busses. Independent under voltage lockout circuits will shut down the corresponding switch if its input voltage falls below the under voltage lockout threshold. If the die temperature reaches the thermal limit, both switches thermal cycle off and on indefinitely without damage until the thermal condition is removed. An open drain FAULT output signals an over current or over temperature condition for each channel. Input logic levels are TTL compatible. The AAT4670 is available in 8 pin SOP, TSSOP or MSOP specified over -40 to 85 C temperature range.
AAT4670
Features
* * * * * * * * * * * *
SmartSwitchTM
2.2V to 5.5V input voltage range 1A current limit per channel 95m typical RDS(ON) Fast transient response: * < 1s response to short circuit Low 18A quiescent current 1A max with Switches off Slew rate controlled Thermal shutdown Fault flags with 3ms blanking Under voltage lockout Temp range -40 to 85C 8-pin SOP, TSSOP or MSOP packages
Applications
* * * * * * Notebook Computer PDA, Subnotebook USB ports Peripheral ports Hot swap supplies Media bay
Typical Application
AAT4670
INA INB EN
7 6 1
INA INB EN GND
OUTA OUTB FAULTA FAULTB
8 5 2 3
OUTA OUTB FAULTA FAULTB
CINA 1F
GND
CINB 1F
4
COUTA 1F
COUTB 1F
GND
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Dual-Input, Dual-Output Load Switches Pin Descriptions
Pin #
1 2 3 4 5 6 7 8
AAT4670
Symbol
EN FAULTA FAULTB GND OUTA INA INB OUTB
Function
Active-low Enable input (Logic low turns the switches on) Open drain output signals over-current for OUTA and over-temperature condition Open drain output signals over-current for OUTB and over-temperature condition Ground connection P-channel MOSFET drain channel A P-channel MOSFET source channel A P-channel MOSFET source channel B P-channel MOSFET drain channel B
Pin Configuration
SOP-8 TSSOP-8
8 7
2
MSOP-8
8 7
EN
1 2 3 4
FAULTA FAULTB GND
6 5
OUTB INB INA OUTA
EN
1 2
FAULTA FAULTB GND
3 4
6 5
OUTB INB INA OUTA
EN
1 2
8 7
FAULTA FAULTB GND
3 4
6 5
OUTB INB INA OUTA
1
1
1
2
2
2
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Dual-Input, Dual-Output Load Switches Absolute Maximum Ratings
Symbol
VINA,B VOUTA,B VFAULTA,B IOUT TJ VESD TLEAD
AAT4670
(TA=25C unless otherwise noted) Value
-0.3 to 6 -0.3 to 6 -0.3 to 6 Internally Limited -40 to 150 4000 300
Description
INA or INB 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 Resistance2 (SOP-8) Maximum Power Dissipation2 (SOP-8)
Value
100 1.25
Units
C/W W
Note 2: Mounted on a demo board.
Electrical Characteristics
-40 to 85C temperature range) Symbol Description
VIN IQ IQ(OFF) ISD(OFF) VUVLO RDS(ON) TCRDS ILIM t1 t2 t3 t4 VEN(L) VEN(H) IEN(SINK) tRESP VFAULTLOW ISINK Tblank TSD Operation Voltage Quiescent Current Off Supply Current Off Switch Current Undervoltage Lockout
(VIN = 5V, TA = 25C unless otherwise noted. Bold values designate Conditions
VINA or VINB = 5V IOUTA = IOUTB = 0 EN = VIN, VINA=VINB =5V, OUTA, OUTB open EN = VIN, VINA=VINB =5V, VOUTA=VOUTB =0V VIN=5.0V VIN=3.0V VOUT < VIN - 0.5V VIN=5V, OUT=0 to 10%, RLOAD=20 VIN=5V, OUT=10% to 90%, RLOAD=20 VIN=5V, OUT=100% to 90%, RLOAD=20 VIN=5V, OUT=90% to 10%, RLOAD=20 VIN=2.7V to 5.5V3 VIN=2.7V to <3.6V VIN=3.6V to 5.5V VEN=5.5V VIN=5V ISINK = 1mA VFAULT = 5.5V 1.0
Min Typ
2.2 18
Max Units
5.5 40 1 1 2.2 130 150 V A A A V
On-Resistance Channel A or B Switch Resistance Tempco Current Limit Channel A or B Output Turn-On Delay Time Output Rise Time Output Turn-Off Delay Time Output Fall Time EN Input Low Voltage EN Input High Voltage EN Input Leakage Current Loop Response FAULT logic Output Low FAULT Logic Output High Leakage Current Fault Blanking Time Over-temperature threshold
0.1 1.7 95 m 105 2800 ppm/C 1.25 1.50 A 100 1000 s 100 1000 s 10 20 s 5 20 s 0.8 V V 0.01 750 0.5 3 125 1 0.4 1 A ns V A ms C
2.0 2.4
Note 3: For VIN outside this range consult typical EN threshold curve. 4670.2004.04.1.0
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Dual-Input, Dual-Output Load Switches Typical Characteristics
Quiescent Current vs. Temperature
30 20 18 25 16 14 12 10 8 6 4 2 0 -40 -20 0 20 40 60 80 100 120 0 1 2 3 4 5 6
AAT4670
Quiescent Current vs. Input Voltage
Quiescent Current (A)
15 10 5 0
Input (A)
20
Temperature (C)
Input (V)
Off-Supply Current vs. Temperature
1.0000
Off-Switch Current vs. Temperature
1.0000
Off-Switch Current (A)
0.1000 0.0100 0.0010 0.0001 0.0000 -40 -20 0 20 40 60 80 100 120
Off-Switch Current (A)
0.1000 0.0100 0.0010 0.0001 0.0000 -40 -20 0 20 40 60 80 100 120
Temperature (C)
Temperature (C)
Current Limit vs. Output Voltage
1.4 1.2 150 140
RDS(ON) vs. Temperature
RDS(ON) (m)
1.0
130 120 110 100 90 80 70 60
Output (A)
0.8 0.6 0.4 0.2 0.0 0 1 2 3 4 5
VIN=3V
VIN=5V
-40
-20
0
20
40
60
80
100
120
Output (V)
Temperature (C)
4
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Dual-Input, Dual-Output Load Switches Typical Characteristics
Turn-ON/OFF Response with 20 1F loads
EN (5V/div) FAULT (5V/div) OUTB (5V/div) INB = 5V OUTA (5V/div) INA = 3V IINA + IINB (200mA/div)
AAT4670
FAULT Delay Start Into 0.6 Load
ON (5V/div) FAULT (5V/div) VOUT (1V/div)
IIN (500mA/div)
100s/div
500s/div
Short Circuit Through 0.6
8 9
Short Circuit Through 0.3
8 12
Input and Output (V)
6
Input Voltage
Input and Output (V)
6
6 4 2 0 -2 -1 0 1 2
Input Voltage
Output (A)
8
4
Output Current Output Voltage
-1 0 1 2 3 4
3
Output Current
4
2
0
0
0
-3
Output Voltage
-4 3 4
Time (s)
Time (s)
Thermal Shutdown Response
2.4
Typical EN Threshold vs. VIN
ON (5V/div) FAULT (5V/div) VOUT (1V/div)
EN Threshold (V)
2.2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 1.5 2 2.5 3 3.5 4 4.5 5 5.5
VEN(H) VEN(L)
IIN (500mA/div)
200ms/div
VIN (V)
Output (A)
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Dual-Input, Dual-Output Load Switches Functional Block Diagram
INA
ILIM UVLO OTMP UVLO ILIM Slew Rate Slew Rate
AAT4670
OUTA
EN
INB
OUTB FAULTA FAULTB
GND
Functional Description
The AAT4670 dual channel load switch, implemented with isolated independent P-channel MOSFET devices, is ideal for applications where dual power supplies are in continuous use. Typical applications for this include products with multiple USB ports, or ports requiring protection that operate off of separate power supplies. The input power supplies can be any voltage between 2.2V and 5.5V in any combination; one supply is not required to be the higher voltage. Internally, the power supply for the control circuitry will automatically switch to the higher of the two supplies. In the case where the supplies are equal, +/- 30mV of hysteresis prevents the internal supply from oscillating between the two input supplies. The low impedance P-channel MOSFET devices are identical in size allowing for layout flexibility. They are controlled by a patented fast acting current loop, and respond to short circuits in a fraction of a microsecond, which eases requirements on the input capacitors. With such fast transient response time, the upstream power supply rail is naturally isolated from the protected port. The AAT4670 is internally protected from thermal damage by an over temperature detection circuit. If a high ambient temperature or an 6
over current condition causes the die temperature to reach 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 or high temperature 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. Since the power devices operate off of independent power supplies, independent under voltage lockout circuits are employed. If the power supply to one channel falls below the under voltage lockout threshold, the other channel will remain active. A current limit condition is reported by the open drain FAULT output associated with the appropriate channel. A thermal limit condition is reported by both FAULT outputs. A three 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 AAT4670 is ideally suited for protection of peripheral ports such as USB, PS2 and parallel ports.
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Dual-Input, Dual-Output Load Switches Applications Information
Input Capacitor
The input capacitors, CINA and CINB, protect the input power supplies from current transients generated by loads attached to the AAT4670. If a short circuit is suddenly applied to an output of the AAT4670, there is a 750 nanosecond period during which a large current flows 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 AAT4670. 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. AAT4670 output from activating the associated 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.
AAT4670
Thermal Considerations
Since the AAT4670 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 AAT4670 at high temperature. RJA is the thermal resistance between the AAT4670 die and the board onto which it is mounted. TA(MAX) is the maximum temperature that the PCB under the AAT4670 would be if the AAT4670 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 the current limit is active, a small capacitance of approximately 1F is required on each output. No matter how big the output capacitor, output current is limited to the value set by the AAT4670 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 AAT4670 will charge at a rate no greater than the current limit setting.
TSD(MIN) is the minimum temperature required to activate the AAT4670 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 120C/W. Using Equation 2, IMAX= 115 - 85 = 1.25 A 160m x 120
FAULT Output
FAULT flags are provided to alert the system if an AAT4670 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, the associated FAULT flag is pulled to ground through approximately 100. Removal of voltage or current transients of less than three milliseconds prevents capacitive loads connected to either
4670.2004.04.1.0
To prevent thermal limiting, the operating load current in the application must be less than 1.25A which lies in the current limiting range, so in this application, any operating current below the current limit threshold is allowed. 7
Dual-Input, Dual-Output Load Switches Timing Diagram
AAT4670
EN
OUT
t1
t2
t3
t4
Ordering Information
Package SOP-8 TSSOP-8 MSOP-8 Marking1 4670 4670 BFXYY Part Number (Tape and Reel) AAT4670IAS-T1 AAT4670IHS-T1 AAT4670IKS-T1
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
8
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Dual-Input, Dual-Output Load Switches Package Information
AAT4670
SOP-8
3.90 0.10 4.90 0.10
6.00 0.20
0.375 0.125 1.55 0.20
45
0.175 0.075
4 4
0.235 0.045 0.825 0.445
0.42 0.09 x 8
1.27 BSC
TSSOP-8
4.40 0.10
6.40 0.20
3.00 0.10 0.65 BSC
12 REF x 4
1.05 MAX
1.20 MAX
0.145 0.055 4 4
0.245 0.055 x 8
0.10 0.05 12
0.60 0.15 1.00 REF
DETAIL A
All dimensions in millimeters. 4670.2004.04.1.0
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Dual-Input, Dual-Output Load Switches
MSOP-8
4 4 1.95 BSC
AAT4670
3.00 0.10
4.90 0.10
0.60 0.20 PIN 1 0.254 BSC 0.95 REF
3.00 0.10 10 5 0.95 0.15 0.85 0.10
0.075 0.075 0.65 BSC 0.30 0.08
All dimensions in millimeters.
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, and advise customers 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 10
4670.2004.04.1.0
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