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AAT4650
5V/3V PC Card Power Switch General Description
The AAT4650 SmartSwitchTM is a single channel PC Card (PCMCIA) power switch. It is used to select between two different voltage inputs, each between 2.7V and 5.5V. An internal switch powers the circuitry from whichever input voltage is higher. The device's output, VCC, is slew rate controlled and current limited, in compliance with PC Card specifications. The current limit response time to a short circuit is typically 1s. The internal P-Channel MOSFET switches are configured to break before make, that is, both switches cannot be closed at the same time. Controlled by a 2 bit parallel interface, the four states for VCC are VCC5, VCC3, Hi-impedance, or Ground. When in the ground state, VCC is pulled to ground by a 5k resistor. An open drain FAULT output is asserted during over-current conditions. During power up slewing, FAULT also signals that VCC is out of tolerance. An internal over temperature sensor forces VCC to a high impedance state when an over-temperature condition exists. Quiescent current is typically a low 15A, as long as ICC is less than approximately 500mA. Above this load current, the quiescent current increases to 200A. The AAT4650 is available in 8-pin SOP and TSSOP packages specified over -40 to 85C.
Features
* * * * * * * * *
SmartSwitchTM
2.7V to 5.5V Input voltage range 85m (5V) typical RDS(ON) Low quiescent current 15A (typ) Reverse-blocking switches Short-circuit protection Over-temperature protection FAULT flag output Temp range -40 to 85C 8 pin SOP or TSSOP package
Preliminary Information
Applications
* * * Notebook Computer PDA, Subnotebook Power Supply Multiplexer Circuit
Typical Application
VCC5 VCC3 CTL1 CTL0 FAULT
CIN5 1F CIN3 1F
8 5 3 2 4 1
VCC5 VCC3 VCC CTL1 AAT4650 CTL0 FAULT GND
6,7
VCC
COUT 0.1F
GND
GND
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AAT4650
5V/3V PC Card Power Switch Pin Descriptions
Pin #
1 2 3 4 5 6 7 8
Symbol
GND CTL0 CTL1 FAULT VCC3 VCC VCC VCC5
Function
Ground connection Control input (see Control Logic Table below) Control input (see Control Logic Table below) Open drain output signals over-current condition 3V supply Output (see Control Logic Table below) Output (see Control Logic Table below) 5V supply
Pin Configuration
SO-8 / TSSOP-8 (Top View)
GND CTL0 CTL1 FAULT
1 2
8 7
3 4
6 5
VCC5 VCC VCC VCC3
1 2
Control Logic Table
CTL1
0 0 1 1
CTL0
0 1 0 1
Function
OFF 5v 3v HiZ
Result
5k VCC to GND VCC=VCC5 VCC=VCC3 Both FETs OFF
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AAT4650
5V/3V PC Card Power Switch Absolute Maximum Ratings
Symbol
VCC3, VCC5 VCC IMAX TJ TLEAD VESD
(TA=25C unless otherwise noted) Value
-0.3 to 6 -0.3 to 6 Current Limited -40 to 150 300 4000
Description
IN to GND OUT to GND Maximum Continuous Switch Current Operating Junction Temperature Range Maximum Soldering Temperature (at Leads) ESD Rating1 -- HBM
Units
V V A C C V
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
Thermal Resistance (SOP-8)2 Power Dissipation (SOP-8)2
Value
100 1.25
Units
C/W W
Note 2: Mounted on an FR4 board.
(VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values are at TA=25C; bold values designate full temperature range) Symbol Description Conditions
OFF mode, VCC=0V VCC=VCCIN -0.5V, ON mode VCC3 or VCC5 selected, TA=25C VCC=3.0v, TA=25C VCC=5.0v, TA=25C 1.0 85 80 2800 500 500 1000 1000
Electrical Characteristics
Min
Typ
Max
1 2.0 110 100
Units
A A m m ppm/C s s s s s s s s s s
VCC Output ICC Hi-Z High impedance Output Leakage Current Iccsc Short Circuit Current Limit
RDS(ON)
On-Resistance
Tcrds Switch Resistance Tempco VCC Switching Time (Refer to Figure 1) t1 Output Turn-On Delay Time t2 Output Turn-On Delay Time t3 Output Rise Time t4 Output Rise Time t5 Output Turn-Off Delay Time t6 Output Turn-Off Delay Time t7 Output Fall Time to OFF State t8 Output Fall Time to OFF State t9 Output Fall Time to Hi-Z State t10 Output Fall Time to Hi-Z State
VCC=0v to 10% of 3.3V, ROUT=10 VCC=0v to 10% of 5.0V, ROUT=10 VCC=10% to 90% of 3.3V, RLOAD=10 VCC=10% to 90% of 5.0V, RLOAD=10 VCC=3.3 to 90% of 3.3V, RLOAD=10 VCC=5.0 to 90% of 5.0V, RLOAD=10 VCC=90% to 10% of 3.3V, RLOAD=10 VCC=90% to 10% of 5.0V, RLOAD=10 VCC=90% to 10% of 3.3V, RLOAD=10 VCC=90% to 10% of 5.0V, RLOAD=10
300 300
2000 1500 3000 3000 400 400 200 200 1500 2000
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AAT4650
5V/3V PC Card Power Switch
Symbol
Description
Conditions
Min
2.7 2.7
Typ
Max Units
5.5 5.5 1 V V A A A A A A V V V A V A
Power Supply VCC3 VCC3 Operation Voltage VCC5 VCC5 Operation Voltage ICC3 VCC3 Supply Current VCC=5V or HiZ or OFF, VCC3VCC3, ICC Out=0 VCC=HiZ, VCC5>VCC3, ICC Out=0 VCC=3.3v, VCC5>VCC3 ,ICC Out=0 VCC=5v, VCC5>VCC3, ICC Out=0
5 10 10 15
ICC5
VCC5 Supply Current
20 1 40 40 40 0.8
Parallel Interface VCTLLOW CTL Input Low Voltage VCTLHI CTL Input High Voltage ISINKCTL VFAULTLOW ISINKFAULT Other OTMP CTL Input leakage FAULT Logic Output Low Voltage FAULT Logic Output High Leakage Current Over Temperature Shutdown
VCC3 or VCC5=2.7 to 3.6V VCC3 or VCC5=4.5 to 5.5V VCTL = 5.5V ISINK=1mA VFAULT= 5.5V
2.0 2.4 0.01 1 0.4 1
0.05
125
degC
Timing Diagram
5 0 5
CTL0,1
Vcc 0 t1, t2 t3, t4 t5, t6 t7, t8 t9, t10
Figure 1: VCC Switching Time Diagram Refer to VCC Switching Time specifications under the Electrical Characteristics section for definitions of t1 to t10.
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AAT4650
5V/3V PC Card Power Switch Typical Characteristics
(Unless otherwise noted, TA = 25C)
Quiescent Current vs. Temperature (ICC5)
2
Current Limit VCC=VCC3
Quiescent Current (A)
30 25 20 15 10 5 0 -40 -20 0 20 40 60 80 100 120
0 0 0.5
VCC3=3V VCC5=5V
CTL0=5V CTL1=0V
1.5
Ta=25C
1
0.5
1
1.5
2
2.5
3
Temperature (C)
Vout
Current Limit VCC=VCC5
Off-Switch Current (A)
2
Off-Switch Current vs. Temperature (ICC3)
1.0000 0.1000 0.0100 0.0010 0.0001 0.0000 -40 -20 0 20 40 60 80 100 120
Ta=25C
1.5
VCC3=3V VCC5=5V
CTL1=0V CTL0=0V
1
0.5
0 0 1 2 3 4 5 6
Vout
Temperature (C)
Off-Switch Current vs. Temperature ICC5
Off-Switch Current (A)
1.0000 0.1000 0.0100 90.0 0.0010 0.0001 0.0000 -40 -20 0 20 40 60 80 100 120 80.0 70.0 60.0 -40 120.0
Rdson vs. Temperature
VCC5=5V VCC3=3V
CTL1=0V CTL0=0V
110.0 100.0
VCC=VCC3=3.0V
VCC=VCC5=5.0V
-20
0
20
40
60
80
100
120
Temperature (C)
Temperature (C)
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AAT4650
5V/3V PC Card Power Switch
(Unless otherwise noted, TA = 25C)
Turn-ON/OFF Response with 10 Ohm 1F load
Turn-ON/OFF Response with 15 Ohm 1F load
CTL1 (5V/div)
FAULT (5V/div)
CTL0 (5V/div) FAULT (5V/div)
VCC (2V/div) IVCC3 (200mA/div)
500s/div
VCC (2V/div)
IVCC5 (200mA/div)
500s/div
Thermal Shutdown Response
CTL1 (5V/div) FAULT (5V/div)
8
Short Circuit Through 0.3 Ohm
11
Input and Output (V)
4
5
VCC (1V/div)
Output Current
2 2
Output Voltage
0 -2 0 2 4 6 8 10 -1
IVCC5 (500mA/div)
100ms / div
Time (s)
Short Circuit Through 0.6 Ohm
8 9
Input and Output (V)
4
Output Current Output Voltage
3
2
0
0 -2 0 2 4 6 8 10
-3
Time (s)
Output (A)
6
Input Voltage
6
6
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Output (A)
6
Input Voltage
8
AAT4650
5V/3V PC Card Power Switch Functional Block Diagram
VCC 3 VCC 5
Body Ctl VCC
Over Current
Over Current
Over Temperature
Slew Rate
Slew Rate
5K FAULT
CTL1 CTL0
Control Logic
GND
Functional Description
The AAT4650 is a single channel power switch that can be used in any application where dual power supply multiplexing is required. Typical applications for this include PC card applications not requiring a 12 volt power supply, or applications where power is switched, for example, between 5 volts for operation and 3.3 volts for standby mode. The AAT4650 operates with input voltages ranging from 2.7 to 5.5 volts in any combination and automatically powers its internal circuitry off of whichever input voltage is higher. Two identical low RDS P-channel MOSFETS serve as the power multiplexing circuit with a common drain as the Vcc output and independent sources as the two Vcc3 and Vcc5 inputs. A two bit parallel interface determines the state of the multiplexer: Vcc=Vcc3, Vcc=Vcc5, Vcc with resistive pull down to ground, or Vcc hi-impedance. When the state is set to either of the two inputs, the multiplex-
ing circuit will slowly slew the VCC output to the new voltage level which protects the upstream power supply from sudden load transients. When the resistive pull down is chosen for VCC, the VCC output is quickly discharged by the resistive pull down. The AAT4650 always serves as an electronic fuse by limiting the load current if it exceeds the current limit threshold. During power up into a short, the current will gradually increase until the current limit is reached. During a sudden short circuit on the output, the current limit will respond in 1 s to isolate and protect the upstream power supply from the load short circuit. In most applications, because the response time is so fast, a short circuit to VCC will not affect the upstream supply, so system functionality will not be affected. In the case of an over current condition, an open drain FAULT flag output will signal the event. The FAULT output is also active during output voltage slew, and becomes inactive once the output is within regulation.
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AAT4650
5V/3V PC Card Power Switch Applications Information
Input Capacitor
Typically a 1F or larger capacitor is recommended for CIN. A CIN capacitor is not required for basic operation, however, it is useful in preventing load transients from affecting up stream circuits. 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. AAT4650 is dominated by voltage regulation rather than by thermal considerations, and is set by either the current limit or the maximum RDS of the P-channel MOSFET. The maximum RDS at 85C is calculated by applying the RDS Tempco to the maximum room temperature RDS: RDS(MAX) = RDS25 x (1 + TC x T), or RDS(MAX) = 105m x (1 + 0.0028 x 60) = 122m The maximum current is equal to the 2% tolerance of the 5 volt supply (100mV) across the AAT4650 divided by RDS(MAX). Or IMAX5 = 100mV / 122m = 820mA For the 3.3 volt supply in the PC card application, the conditions are a bit relaxed, with the allowable voltage regulation drop equal to 300mV. With a 2% supply, and 1% PCB trace regulation, the PC card switch can have a 200mV drop. So IMAX3 = 200mV / 134m = 1.5A Since 1.5A is the nominal current limit value, the AAT4650 will current limit before IMAX3 is reached. Thermal issues are not a problem in the SO-8 package since JA, the package thermal resistance, is only 120C/W. At any given ambient temperature (TA) the maximum package power dissipation can be determined by the following equation: PD(MAX) = [TJ(MAX) - TA] / JA Constants for the AAT4650 are maximum junction temperature, TJ(MAX) = 125C, and package thermal resistance, JA = 120C/W. Worst case conditions are calculated at the maximum operating temperature where TA = 85C. Typical conditions are calculated under normal ambient conditions where TA = 25C. At TA = 85C, PD(MAX) = 333mW. At TA = 25C, PD(MAX) = 833mW. Maximum current is given by the following equation: IOUT(MAX) = (PD(MAX) / RDS)1/2 For the AAT4650 at 85C, IOUT(MAX) = 1.65A, a value greater than the internal minimum current limit specification.
Output Capacitor
A 0.1F or greater capacitor is generally required between Vcc and GND. Likewise, with the output capacitor, there is no specific capacitor ESR requirement. If desired, COUT may be increased to accommodate any load transient condition.
Parallel Interface / Break Before Make
A two bit parallel interface determines the state of the Vcc output. The logic levels are compatible with CMOS or TTL logic. A logic low value must be less than 0.8 volts, and a logic high value must be greater than 2.4 volts. In cases where the interface pins rapidly change state directly from 3v to 5v (or vice versa), internal break before make circuitry prevents any back flow of current from one input power supply to the other. In addition, the body connections of the internal P-channel MOSFET switches are always set to the highest potential of Vcc3, Vcc5, or Vcc, which prevents any body diode conduction, power supply backflow, or possible device damage.
FAULT Output
The FAULT output is pulled to ground by an open drain N-channel MOSFET during an over current or output slew condition. It should be pulled up to the reference power supply of the controller IC via a nominal 100K resistor.
Voltage Regulation
The PC Card Specification calls for a regulated 5 volt supply tolerance of +/-5%. Of this, a typical power supply will drop less than 2%, and the PCB traces will drop another 1%. This leaves 2% for the AAT4650 as the PC card switch. In the PC card application, the maximum allowable current for the 8
Overcurrent and Overtemperature Protection
Because many AAT4650 applications provide power to external devices, it is designed to protect its host device from malfunctions in those peripherals
4650.2001.10.0.93
AAT4650
5V/3V PC Card Power Switch
through slew rate control, current limiting, and thermal limiting. The AAT4650 current limit and thermal limit serve as an immediate and reliable electronic fuse without any increase in RDS for this function. Other solutions such as a poly fuse do not protect the host power supply and system from mishandling, or short circuited peripherals, they will only prevent a fire. The AAT4650 high speed current limit and thermal limit not only prevent fires, they also isolate the power supply and entire system from any activity at the external port, and report a mishap by means of a FAULT signal. Overcurrent and overtemperature go hand in hand. Once an overcurrent condition exists, the current supplied to the load by the AAT4650 is limited to the overcurrent threshold. This results in a voltage drop across the AAT4650 which causes excess power dissipation and a package temperature increase. As the die begins to heat up, the overtemperature circuit is activated. If the temperature reaches the maximum level, the AAT4650 automatically switches off the P-channel MOSFETs. While they are off, the overtemperature circuit remains active. Once the temperature has cooled by approximately 10C, the P-channel MOSFETs are switched back on. In this manner, the AAT4650 is thermally cycled on and off until the short circuit is removed. Once the short is removed, normal operation automatically resumes. To save power, the full high speed overcurrent circuit is not activated until a lower threshold of current (approximately 700mA) is exceeded in the power device. When the load current exceeds this crude threshold, the AAT4650 quiescent current increases from 15A to 150A. The high speed overcurrent circuit works by linearly limiting the current when the current limit is reached. As the voltage begins to drop on Vcc due to current limiting, the current limit magnitude varies, and generally decreases as the Vcc voltage drops to 0 volts.
Switching Vcc Voltage
The AAT4650 meets PC card standards for switching the Vcc output by providing a ground path for Vcc as well as a hi impedance state. The PC card protocol for determining low voltage operations is to first power the peripheral with 5 volts and poll for 3.3 volt operation. When transitioning from 5 volts to 3.3 volts, Vcc must be discharged to less than 0.8 volts to provide a hard reset. The resistive ground state (CTL1=0, CTL0=0) will accommodate this. The ground state will also guarantee the Vcc voltage to be discharged within the specified 100ms amount of time.
Printed Circuit Board Layout Recommendations
For proper thermal management, to minimize PCB trace resistance, and to take advantage of the low RDS(ON) of the AAT4650, a few circuit board layout rules should be followed: Vcc3, Vcc5, and Vcc should be routed using wider than normal traces, the two Vcc pins (6 and 7) should be connected to the same wide PCB trace, and GND should be connected to a ground plane. For best performance, CIN and COUT should be placed close to the package pins.
Typical PC Card Application Circuit
Power 5V Supply 3.3V
CIN5 1F CIN3 1F
8 5 3 2 4 1 100K
PC Card Controller
VCC
VCC5 VCC3 CTL1 AAT4650 VCC CTL0 FAULT GND
6,7
PC Card Slot
VCC COUT 0.1F
FAULT CTL1 CTL0
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AAT4650
5V/3V PC Card Power Switch Evaluation Board Layout
The AAT4650 evaluation layout follows the printed circuit board layout recommendations, and can be used for good applications layout. Note: Board layout shown is not to scale.
Figure 2: Evaluation board top side silk screen layout / assembly drawing
Figure 3: Evaluation board component side layout
Figure 4: Evaluation board solder side layout
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AAT4650
5V/3V PC Card Power Switch Ordering Information
Package SO-8 TSSOP-8 Marking Part Number Bulk AAT4650IAS-B1 AAT4650IHS-B1 Tape and Reel AAT4650IAS-T1 AAT4650IHS-T1
Package Information
SOP-8
Dim A A1 A2 B C D E e H L Y 1
EH
D
7 (4x) A A2
Q
c
Millimeters Min Max 1.35 1.75 0.10 0.25 1.45 0.33 0.51 0.19 0.25 4.80 5.00 3.80 4.00 1.27 5.80 6.20 0.40 1.27 0.00 0.10 0 8
Inches Min Max 0.053 0.069 0.004 0.010 0.057 0.013 0.020 0.007 0.010 0.189 0.197 0.150 0.157 0.050 0.228 0.244 0.016 0.050 0.000 0.004 0 8
b y
e
A1 L
Note: 1. PACKAGE BODY SIZES EXCLUDE MOLD FLASH PROTRUSIONS OR GATE BURRS. 2. TOLERANCE 0.1000mm (4mil) UNLESS OTHERWISE SPECIFIED 3. COPLANARITY: 0.1000mm 4. DIMENSION L IS MEASURED IN GAGE PLANE. 5. CONTROLLING DIMENSION IS MILLIMETER; CONVERTED INCH DIMENSIONS ARE NOT NECESSARILY EXACT.
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AAT4650
5V/3V PC Card Power Switch
TSSOP-8 Millimeters Min Max 1.05 1.20 0.05 0.15 1.05 0.25 0.30 0.127 2.90 3.10 9.60 9.80 4.30 4.50 6.20 6.60 0.65 BSC 0.50 0.70 1.0 0.09 0.09 0 8 Inches Min Max 0.041 0.047 0.002 0.006 0.041 0.010 0.012 0.005 0.114 0.122 0.378 0.386 0.170 0.177 0.244 0.260 0.025 BSC 0.20 0.028 0.039 0.004 0.004 0 8 12
Dim A A1 A2 b c D-8 D-28 E E1 e L L1 R R1 1 2
E
E1
DETAIL A
1
2
D
E
0.20
e
R1
A2
A
R
1
A1 b DETAIL A
2
L L1
Advanced Analogic Technologies, Inc.
1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086 Phone (408) 524-9684 Fax (408) 524-9689 12
4650.2001.10.0.93

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