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USB Single-Channel Power Switch General Description
The AAT4625 SmartSwitchTM is part of AnalogicTechTM's Application Specific Power MOSFETTM (ASPMTM) product family. It is a 1.0A Current Limited P-channel, MOSFET power switch designed for high-side load-switching applications. This switch operates with inputs ranging from 2.7V to 5.5V, making it ideal for both 3V and 5V systems. An integrated current-limiting circuit protects the input supply against large changes in load current which may cause the supply to fall out of regulation. The AAT4625 is also protected from thermal overload which limits power dissipation and junction temperatures. The current limit threshold is factory programmed at 1.5A, with a maximum of 2.0A. The quiescent supply current is typically a low 16A. In shutdown mode, the supply current decreases to less than 1A. The AAT4625 is available in 8 pin SOP, TSSOP, or MSOP and is 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. Single versions with adjustable current limit (AAT4601) or fixed current limit (AAT4625) as well as dual versions with fixed current limit (AAT4626) are available.
AAT4625
Features
* * * * * * * * * * * * *
SmartSwitchTM
Compliant with USB 1.1 and 2.0 specifications 2.7V to 5.5V Input voltage range 1.0A minimum continuous current 2.0A maximum current limit 60m typical RDS(ON) Low quiescent current * Typically 16A * 1A max with Switch off Thermal shutdown Slew rate limited turn on Fault flag with 10ms blanking Undervoltage Lockout Temp range -40 to 85C UL Approved--File No. E217765 8 pin SOP, TSSOP, or MSOP package
Applications
* * * * USB ports and peripherals Notebook computers Hot swap supplies General purpose power switching
UL Recognized Component
Typical Application
VCC 5.0V 100k
2 1 7
IN
OUT
6
OUTPUT
AAT4625
FLG EN (EN)
3
OUT
8
0.1F
EN (EN)
120F
GND
GND
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USB Single-Channel Power Switch Pin Descriptions
Pin #
1
AAT4625
Symbol
EN (EN)
Function
Enable Input: Logic-compatible enable input. High input > 2.1V typical. Low input < 1.9V typical. Active high or active low option available; see Ordering Information for details. Fault Flag Output: Active-low, open-drain output. Indicates over current, UVLO and thermal shutdown. Ground connection Not internally connected. Switch Output: These pins are the P-channel MOSFET drain connection. Supply Input: This pin is the P-channel MOSFET source connection. Also supplies the IC's internal circuitry.
2 3 4,5 6,8 7
FLG GND NC OUT IN
Pin Configuration
SOP-8 TSSOP-8 MSOP-8 (Top View)
EN (EN) FLG GND NC
1 2
8 7
3 4
6 5
OUT IN OUT NC
1 2
2
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USB Single-Channel Power Switch Absolute Maximum Ratings
Symbol
VIN VFLG IFLG VOUT IOUT VEN TS TLEAD (TA=25C unless otherwise noted)
AAT4625
Description
IN to GND FLG to GND FLG Current OUT to GND Output Current (Internally Limited) EN to GND Storage Temperature Maximum Soldering Temperature (at Leads)
Value
-0.3 to 6 -0.3 to 6 50 -0.3 to VIN+0.3 2.0 -0.3 to 6 150 300
Units
V V mA V A V C 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.
Thermal Information
Symbol
JA JA JA PD PD PD
Description
Maximum Thermal Resistance (SOP-8)
1
Value
120 150 150 1.0
1
Units
C/W C/W C/W W mW mW
Maximum Thermal Resistance (TSSOP-8)1 Maximum Thermal Resistance (MSOP-8) Maximum Power Dissipation (SOP-8)1 Maximum Power Dissipation (TSSOP-8) Maximum Power Dissipation (MSOP-8)1
1
833 833
Note 1: Mounted on an FR4 printed circuit board.
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USB Single-Channel Power Switch
(VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values are at TA=25C; bold values designate full temperature range) Symbol
VIN IQ IQ(OFF) VEN-THRSH IEN CEN Rds(ON) TON TON-RISE TOFF TOFF-FALL ISD(OFF) ILIMIT OTMP RFLG ISINK VUVLO TBLANK
AAT4625
Electrical Characteristics
Description
Operation Voltage Quiescent Current Off Supply Current Enable Input Threshold Enable Input Current Enable Input Capacitance On-Resistance Output Turn-On Delay Output Turn-On Rise Time Output Turn-Off Delay Output Turn-Off Fall Time Output Leakage Current Current Limit Threshold
Conditions
VIN=5V, EN=active VIN=5.5V, EN (EN)=inactive Low-to-high transition High-to-low transition VEN = 0V to 5.5V VIN =5V, TA = 25C VIN =3.0V, TA = 25C VIN =5V, RL=10 VIN =5V, RL=10 VIN =5V, RL=10 VIN =5V, RL=10 EN=inactive, VIN=5.5V, VOUT=0V ramped load applied to enable output, VOUT < 4.0V TJ increasing TJ decreasing VIN =5V, IL = 1mA VFLG = 5.5V VIN = increasing, 1% hysteresis
Min
2.7
Typ
16
Max
5.5 30 1 2.4 1 100 115
Units
V A A V V A pF m m ms ms s s A A C C A V ms
0.8 0.01 1 60 70 0.25 0.2 5 0.03 1.5 125 115 30 0.05 2.3 10
1.0
20 20 15 2.0
Over Temperature Shut Down Error Flag Output Resistance Error Flag Off Current Under voltage Lockout FAULT blanking
2.0
1 2.7
4
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USB Single-Channel Power Switch Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C)
Quiescent Current vs. Temperature
Quiescent Current (A)
30 25 20 15 10 5 0 -40 -20 0 20 40 60 80 100 120 20 18 16
AAT4625
Quiescent Current
Input (A)
14 12 10 8 6 4 2 0 0 1 2 3 4 5 6
Temperature (C)
Input (V)
Current Limit
1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5
Off-Supply Current vs. Temperature
1.0000
Off-Supply Current (A)
Output (A)
0.1000
0.0100
0.0010 -40 -20 0 20 40 60 80 100 120
Output (V)
Temperature (C)
Off-Switch Current vs. Temperature
1.0000
Turn-ON/OFF Response with 10 Ohm 1F load
EN (5V/div)
Off-Switch Current (A)
0.1000 0.0100 0.0010 0.0001 0.0000 -40 -20 0 20 40 60 80 100 120
FAULT
Vout (2V/div)
Iin (200mA/div)
100 /di
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USB Single-Channel Power Switch
(Unless otherwise noted, VIN = 5V, TA = 25C)
Start Into 1 Ohm load
AAT4625
Thermal Shutdown Response
EN (5V/div) FAULT (5V/div) Vout (1V/div) Iin (500mA/div)
50ms / div
EN (5V/div)
FAULT (5V/div) Vout (1V/div) Iin (500mA/div)
1ms/div
Short Circuit Through 0.3 Ohm
8 12
8
Short Circuit Through 0.6 Ohm
9
Input and Output (V)
Input and Output (V)
Output (A)
4
Output Current Output Voltage
-1 0 1 2 3 4 5
4
4
Output Current Output Voltage
3
2
0
2
0
0
-4
0 -1 0 1 2 3 4 5
-3
Time (s)
Time (s)
Rds(ON) vs. Temperature
80.0 75.0 70.0 65.0 60.0 55.0 50.0 45.0 40.0 -40 -20 0 20 40 60 80 100 120
VCC=3V
VCC=5V
Temperature (C)
6
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Output (A)
6
Input Voltage
8
6
Input Voltage
6
USB Single-Channel Power Switch Functional Block Diagram
AAT4625
IN
OUT
Over-Temp Protection
Undervoltage Lockout
FLG EN (EN)
1.2V Reference Current Limit
GND
Functional Description
The AAT4625 is an integrated MOSFET load switch with a fixed current limit, over temperature protection, level shifted input and a fault flag. The current limit control is combined with an over temperature thermal limit circuit to provide a comprehensive system to protect the load switch under short circuit or other adverse operating conditions. The AAT4625 is ideally suited for control and protection of peripheral ports such as USB, RS232 and parallel ports. The current limit and over temperature circuits will act independently. The device current limit is activated when the output load current exceeds a preset internal threshold level. The minimum current limit threshold characteristic is specified by ILIM(MIN). If the load switch ambient temperature becomes excessive or if a short circuit condition persists, the die temperature will rise causing the over temperature protection circuit to activate.
If the current limit or over temperature protection circuits are active for more then two milliseconds, the system will be informed via the FAULT Flag. A ten millisecond fault blanking delay allows the AAT4625 to be turned on into large capacitive loads without activating the FAULT Flag. The open drain FAULT output can be connected directly to system controllers driven by voltage levels less than the IN pin voltage without additional level shifting circuitry. The load switch is turned on and off by applying a logic level signal to the EN pin. The AAT4625 enable function is available in both active high and active low logic level versions. The AAT4625 typically consumes 16A when operating, when off, the device draws less then 1A. In the off state, current is prevented from flowing between the input and output. The EN function has logic level thresholds that allow the AAT4625 to be TTL compatible and may also be controlled by 2.5V to 5.0V CMOS circuits. The voltage level on either EN or FAULT should not exceed the input supply level present on the IN pin.
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USB Single-Channel Power Switch Applications Information
Operation in Current Limit
If an excessive load is applied to the output of an AAT4625, the load current will be limited by the AAT4625's current limit circuitry. Refer to the "Current Limit" figure in the typical characteristics section of this data sheet. If a short circuit were to occur on the load, there would be a demand for more current than what is allowed by the internal current limiting circuit and the voltage at the device output will drop. This causes the AAT4625 to dissipate more power than in normal operation, causing the die temperature to increase. When die temperature exceeds the internal over temperature threshold, the AAT4625 will shut down. After shutting down, the AAT4625 cools to a level below the over temperature threshold, at which point it will start up again. The AAT4625 will continue to cycle off and on until one of the following events occurs; the load current is reduced to a level below the AAT4625's current limit setting, the input power is removed, or until the output is turned off by a logic high level applied to the EN pin. TSD(MIN) - TA(MAX) RDS(ON)(MAX) x RJA
AAT4625
IMAX=
TSD(MIN) is the minimum temperature required to activate the device over temperature protection. The typical thermal limit temperature specification is 125C for the AAT4625, for calculations, 115C is a safe minimum value to use. For example, a portable device is specified to operate in a 50C environment. The printed circuit board assembly will operate at temperatures as high as 85C. This portable device has a sealed case and the area of the printed board assembly is relatively small causing RJA to be approximately 120C/W. Using Equation 2, IMAX= 115 - 85 = 1.4 A 130 x 120
If this system requires less than 1.4 A, the thermal limit will not activate during normal operation.
Input Capacitor
The input capacitor serves two purposes. First, it protects the source power supply from transient current effects generated by the application load circuit. If a short circuit is suddenly applied to the output of an AAT4625, there is a microsecond long period during which a large current can flow before the current limit circuit becomes active. Refer to the characteristic curve named "Short Circuit Through 0.3." A properly sized input capacitor can dramatically reduce the load switch input transient response effects seen by the power supply and other circuitry upstream from the AAT4625. The second purpose of the input capacitor is to prevent transient events generated by the load circuit from effecting the operation of the AAT4625. For example, if an AAT4625 is used in a circuit that operates from a 5 volt power supply with poor step load response, it is possible that turning on the load switch could cause the input power supply to droop below the AAT4625's under voltage lockout threshold. This drop in voltage would cause the AAT4625 to turn off until the input power supply voltage levels recovers. Since this cycle would be self-perpetuating, the entire circuit could be seen to be unstable. In the very rare case where capacitor cost is prohibitive and the input capacitor is omitted, the output load circuit should be slew rate limited when turned on.
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Thermal Considerations
Since the AAT4625 has internal current limit and over temperature protection, junction temperature is rarely a concern. If an application requires a large load current in a high temperature operating environment, there is the possibility that the over temperature protection circuit rather than the current limit circuit will regulate the current available to the load. In these applications, the maximum current available without risk of activation of the over temperature circuit can 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 AAT4625 at high temperature. RJA is the thermal resistance between the device die and the board onto which it is mounted. TA(MAX) is the maximum ambient temperature for the printed circuit board assembly under the AAT4625 when the load switch is not dissipating power. Equation 1 can be transformed to provide IMAX; Refer to Equation 2. 8
USB Single-Channel Power Switch
Output Capacitor
In order to insure stability while the device current limit is active, a small capacitance of approximately 1F should be used. When the AAT4625 is activated using the ON function, there are no momentary current transients as in the case of when a short circuit suddenly applied to a device that is already on. Refer to the characteristic curve named "TurnOn/OFF Response". Regardless of output capacitor size, output current is limited to the value allowed by the threshold determined by the internal current limiting circuitry. Refer to the internal current limit threshold specifications stated in the electrical characteristics section of this datasheet. This permits very large output capacitors to be used. For example, USB ports are specified to have at least 120F of down stream capacitance from their controlling power switch. An output capacitance as large as 1000F would not disturb the input power supply to an AAT4625 used to control a USB port. 2.5 volts to 5 volts. The EN function control voltage level should not exceed the input supply level applied to the IN pin.
AAT4625
Fault Flag Output
The AAT4625 features an active low fault flag output. The fault flag is provided to alert the system if the over current or over temperature circuits become active or if the load switch is not receiving a sufficient voltage level to operate properly. If either the current limit or over temperature circuits in any combination are constantly active for more than approximately ten milliseconds, the FAULT pin is pulled to ground internally through an open drain device. The 10 millisecond delay on the FAULT function is intended to prevent capacitive loads connected to the load switch output from activating FAULT flag when the device is turned on. The placement of a pull up resistor between the FAULT pin and the IN pin is recommended. Reasonable values for the pull up resistor should range from 10k to 100k. Since FAULT flag is an open drain terminal, it may be pulled up to any voltage that is not greater than the level present on the IN pin. This is done to allow the AAT4625 to signal ancillary circuitry that is powered by voltage levels less than the level on the IN pin. If a fault flag delay greater then 10ms is required, addition delay may be added by use of an RC filter. Referencing to Figure 1, an RC filter can be added to the fault flag output.
EN Input
The AAT4625 is available in both active high EN enable and active low (EN) enable versions. For specific part numbers, refer to the ordering information section. When the AAT4625 is in the off state, the output is an open circuit and the device quiescent current consumption is reduced to less than 1A. The EN threshold voltage is set to allow the AAT4625 to be controlled by 5 volt TTL levels as well as CMOS compatible levels ranging from
V+ 100k R1 10k 1 2 3 C1 0.1F 4
USB Controller Over Current Flag Input
AAT4625
EN FLG GND NC OUT IN OUT NC 8 7 6 5
Figure 1: Fault Flag delay RC filter
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USB Single-Channel Power Switch
Reverse Voltage
The AAT4625 is designed to control current flowing from IN to OUT. If a voltage is applied to OUT which is greater than that on IN, a large resulting reverse current may flow, potentially damaging the AAT4625.
AAT4625
Hot-Plug Applications
Application circuit cards with a high in-rush current potential can be limited by use of the AAT4625. The AAT4625 has both slew rate limited turn on characteristics and a current limit controlled output which make it ideally suited for power port hot-plug applications. A host power back plane or hot plug receptacle may be sensitive to short duration high power surges. The AAT4625 will turn on in a linear ramping fashion and regulate the inrush current with in the specified current limit for the device. The error flag usually will not be effected during application turn on since the 10ms Flag blanking time is intended for these types of events. If an application turn on current surge exceeds 10ms, an RC delay filter may be added to the Flag output to prevent the system from receiving an error during the start up sequence.
Under Voltage Lockout
The AAT4625 has been designed with an under voltage lockout (UVLO) control circuit. The under voltage lockout prevents the output MOSFET device from turning on until the VIN exceeds the typical UVLO threshold of 2.3 volts. During operation, the device will automatically shutdown if VIN falls below the UVLO threshold and the fault flag will be toggled.
Cable / Connector to Hot-Plug Port VBUS Hot-Plug Receptacle GND
v+
AAT4625
1 2 3 0.1F 4 EN FLG GND NC OUT IN OUT NC 8 7 6 5 CBULK (120F)
Card Application Circuit
GND
Inrush Current Protected Application Card
Figure 2: AAT4625 Inrush Current Protected Application
PCB Layout Information
In order to obtain the maximum performance from the AAT4625, very careful attention must be considered in regard to the printed circuit board layout. In most port power switch and port protection appli-
cations, high voltage and current transient events will occur. Proper PCB layout can help reduce the effects of transient events. PCB trace resistance will effect over all circuit transient response, in addition small voltage drops will be incurred.
10
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USB Single-Channel Power Switch
Refer to the following guide lines for power port PCB layout: 1. PCB traces should be kept as short and direct as possible to minimize the effects of the PCB on circuit performance. 2. Make component solder pads large to minimize contact resistance 3. The AAT4625 output bulk capacitor and ferrite beads should be placed as close to the device as possible. PCB traces to the output connector should be kept as short as possible to minimized trace resistance and the associated voltage drop (I2R loss). 4. If ferrite beads are used in the circuit, select ferrite beads with a minimum series resistance. 5. The use of PCB trace vias should be avoided on all traces that conduct high currents. If vias are necessary, make the vias as large as possible and use multiple vias connected in parallel to minimize their effect.
AAT4625
Trace Resistance 0.01ohms (5mV)
P-Channel Mosfet Switch On Resistance 0.06ohms (30mV)
Ferrite Bead and PCB trace resistance 0.02ohms (10mV)
Cable, Connector and Contact Resistance 0.03ohms (15mV)
V+ Input Power Supply 4.50V to 5.25V GND
(5mV) (10mV) (15mV)
VBUS CBULK 0.1F AAT4625 GND CBULK 0.1F
Downstream Peripheral Port 500mA Max. Load Current
Total Voltage Drop = 60mV
Figure 3: Summary of typical circuit voltage drops caused by AAT4625 circuit components and PCB trace resistance.
Evaluation Board Layout
The AAT4625 evaluation layout follows the recommend printed circuit board layout procedures and can be used as an example for good application
layouts. Note that ferrite beards are not used on this simple device evaluation board. The board layout shown is not to scale.
Figure 4: Evaluation board component side layout
Figure 5: Evaluation board solder side layout
Figure 6: Evaluation board top side silk screen layout / assembly drawing
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USB Single-Channel Power Switch
Application Circuits
Ferrite Beads
AAT4625
VBUS = 5.0V CIN R1 0.1F 100k
7
IN
OUT
6,8
VBUS COUT1 0.1F COUT2 120F D+ DGND
AAT4625
2 1 FLG EN(EN) 3 NC 4,5
USB Controller Error Flag On/Off
DATA
Figure 7: Typical USB Host Port Application
Vcc 5.0V 4.50V to 5.25V Upstream V BUS 100mA Maximum VBUS D+ DGND 1F 100k AAT3220-3.3
IN OUT GND
3.3V USB Controller
VIN ON/OFF Over Current Flag GND
AAT4625
EN FLG GND NC OUT IN OUT NC
Ferrite Beads
USB Port VBUS D+
120F
0.1F DGND
1F
Data
Data
Figure 8: Self-Powered Single Port USB Hub
100k USB Host VBUS D+ DGND 1F AAT3220-3.3
IN OUT GND
3.3V USB Controller
VIN ON/OFF Over Current Flag GND
AAT4625
EN FLG GND NC OUT IN OUT NC
Ferrite Beads
USB Port VBUS D+
120F
0.01F DGND
1F
Data
Data
Figure 9: USB Bus Powered Single Port USB Hub
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USB Single-Channel Power Switch Ordering Information
Package SOP8 SOP8 TSSOP8 TSSOP8 MSOP8 MSOP8 Enable EN (Active-high) EN (Active-low) EN (Active-high) EN (Active-low) EN (Active-high) EN (Active-low) Marking1 4625-1 4625 4625-1 4625 DDXYY DCXYY Part Number (Tape and Reel) AAT4625IAS-1-T1 AAT4625IAS-T1 AAT4625IHS-1-T1 AAT4625IHS-T1 AAT4625IKS-1-T1 AAT4625IKS-T1
AAT4625
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
Package Information
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
All dimensions in millimeters.
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USB Single-Channel Power Switch
TSSOP-8
AAT4625
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.
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USB Single-Channel Power Switch
MSOP-8
4 4 1.95 BSC
AAT4625
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.
GAUGE PLANE
0.155 0.075
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USB Single-Channel Power Switch
AAT4625
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 16
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