SmartSwitch
TM
AAT4670
Dual-Input, Dual-Output Load Switches
Preliminary
Information
4670.2002.1.0.92
1
General Description
The AAT4670 SmartSwitchTM is part of the Analogic
Tech Application Specific Power MOSFET
(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.
Features
2.2V to 5.5V input voltage range
1A current limit per channel
95m
typical R
DS(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
INA
C
INA
1
F
C
INB
1
F
INB
EN
FAULTA
OUTA
GND
AAT4670
7
6
1
4
8
INA
INB
GND
GND
OUTA
EN
FAULTA
FAULTB
FAULTB
OUTB
5
OUTB
2
3
C
OUTA
1
F
C
OUTB
1
F
AAT4670
Dual-Input, Dual-Output Load Switches
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4670.2002.1.0.92
Pin Descriptions
Pin Configuration
SOP-8
TSSOP-8
MSOP-8
1
2
EN
FAULTA
GND
FAULTB
OUTB
INB
INA
OUTA
1
2
3
4
8
7
6
5
1
2
OUTB
INB
INA
OUTA
8
7
6
5
EN
FAULTA
GND
FAULTB
1
2
3
4
1
2
EN
FAULTA
GND
FAULTB
1
2
3
4
OUTB
INB
INA
OUTA
8
7
6
5
Pin #
Symbol
Function
1
EN
Active-low Enable input (Logic low turns the switches on)
2
FAULTA
Open drain output signals over-current for OUTA and over-temperature condition
3
FAULTB
Open drain output signals over-current for OUTB and over-temperature condition
4
GND
Ground connection
5
OUTA
P-channel MOSFET drain channel A
6
INA
P-channel MOSFET source channel A
7
INB
P-channel MOSFET source channel B
8
OUTB
P-channel MOSFET drain channel B
AAT4670
Dual-Input, Dual-Output Load Switches
4670.2002.1.0.92
3
Absolute Maximum Ratings
(T
A
=25C unless otherwise noted)
Note: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at con-
ditions 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
Note 2: Mounted on a demo board.
Electrical Characteristics
(V
IN
= 5V, T
A
= 25C unless otherwise noted. Bold values designate
-40 to 85C temperature range)
Note 3: For V
IN
outside this range consult typical EN threshold curve.
Symbol
Description
Conditions
Min
Typ
Max
Units
V
IN
Operation Voltage
2.2
5.5
V
I
Q
Quiescent Current
V
INA
or V
INB
= 5V I
OUTA
= I
OUTB
= 0
18
40
A
I
Q(OFF)
Off Supply Current
EN = V
IN
, V
INA
=V
INB
=5V, OUTA, OUTB open
1
A
I
SD(OFF)
Off Switch Current
EN = V
IN
, V
INA
=V
INB
=5V, V
OUTA
=V
OUTB
=0V
0.1
1
A
V
UVLO
Undervoltage Lockout
1.7
2.2
V
R
DS(ON)
On-Resistance Channel A or B
V
IN
=5.0V
95
130
m
V
IN
=3.0V
105
150
T
CRDS
Switch Resistance Tempco
2800
ppm/C
I
LIM
Current Limit Channel A or B
V
OUT
< V
IN
- 0.5V
1.0
1.25
1.50
A
t
1
Output Turn-On Delay Time
V
IN
=5V, OUT=0 to 10%, R
LOAD
=20
100
1000
s
t
2
Output Rise Time
V
IN
=5V, OUT=10% to 90%, R
LOAD
=20
100
1000
s
t
3
Output Turn-Off Delay Time
V
IN
=5V, OUT=100% to 90%, R
LOAD
=20
10
20
s
t
4
Output Fall Time
V
IN
=5V, OUT=90% to 10%, R
LOAD
=20
5
20
s
V
EN(L)
EN Input Low Voltage
V
IN
=2.7V to 5.5V
3
0.8
V
V
EN(H)
EN Input High Voltage
V
IN
=2.7V to <3.6V
2.0
V
V
IN
=3.6V to 5.5V
2.4
I
EN(SINK)
EN Input Leakage
V
EN
=5.5V
0.01
1
A
t
RESP
Current Loop Response
V
IN
=5V
750
ns
V
FAULTLOW
FAULT logic Output Low
I
SINK
= 1mA
0.4
V
I
SINK
FAULT Logic Output High
V
FAULT
= 5.5V
0.5
1
A
Leakage Current
T
blank
Fault Blanking Time
3
ms
T
SD
Over-temperature threshold
125
C
Symbol
Description
Value
Units
JA
Maximum Thermal Resistance
2
(SOP-8)
100
C/W
P
D
Maximum Power Dissipation
2
(SOP-8)
1.25
W
Symbol
Description
Value
Units
V
INA,B
INA or INB to GND
-0.3 to 6
V
V
OUTA,B
OUTA or OUTB to GND
-0.3 to 6
V
V
FAULTA,B
FAULTA or FAULTB to GND
-0.3 to 6
V
I
OUT
Output Current
Internally Limited
A
T
J
Operating Junction Temperature Range
-40 to 150
C
V
ESD
ESD Rating
1
- HBM
4000
V
T
LEAD
Maximum Soldering Temperature (at Leads)
300
C
Typical Characteristics
R
DS(ON)
vs. Temperature
60
70
80
90
100
110
120
130
140
150
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
R
DS(ON)
(m
)
V
IN
=3V
V
IN
=5V
Current Limit vs. Output Voltage
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0
1
2
3
4
5
Output (V)
Output (A)
Off-Switch Current vs. Temperature
0.0000
0.0001
0.0010
0.0100
0.1000
1.0000
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
Off-Switch Current (
A)
Off-Supply Current vs. Temperature
0.0000
0.0001
0.0010
0.0100
0.1000
1.0000
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
Off-Switch Current (
A)
Quiescent Current vs. Input Voltage
0
2
4
6
8
10
12
14
16
18
20
0
1
2
3
4
5
6
Input (V)
Input (
A)
Quiescent Current vs. Temperature
0
5
10
15
20
25
30
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
Quiescent Current (
A)
AAT4670
Dual-Input, Dual-Output Load Switches
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4670.2002.1.0.92
Typical Characteristics
Typical EN Threshold vs. V
IN
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
1.5
2
2.5
3
3.5
4
4.5
5
5.5
V
IN
(V)
EN Threshold (V)
V
EN(L)
V
EN(H)
Thermal Shutdown Response
200ms/div
ON (5V/div)
FAULT (5V/div)
V
OUT
(1V/div)
I
IN
(500mA/div)
Short Circuit Through 0.3
-2
0
2
4
6
8
-1
0
1
2
3
4
Time (
s)
Input and Output (V)
-4
0
4
8
12
Output (A)
Input Voltage
Output Current
Output Voltage
Short Circuit Through 0.6
0
2
4
6
8
-1
0
1
2
3
4
Time (
s)
Input and Output (V)
-3
0
3
6
9
Output (A)
Input Voltage
Output Current
Output Voltage
FAULT Delay
Start Into 0.6
Load
500
s/div
ON (5V/div)
FAULT (5V/div)
V
OUT
(1V/div)
I
IN
(500mA/div)
Turn-ON/OFF Response with 20
1
F loads
100
s/div
EN (5V/div)
FAULT (5V/div)
OUTB (5V/div) INB = 5V
OUTA (5V/div) INA = 3V
I
INA
+ I
INB
(200mA/div)
AAT4670
Dual-Input, Dual-Output Load Switches
4670.2002.1.0.92
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AAT4670
Dual-Input, Dual-Output Load Switches
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4670.2002.1.0.92
Functional Description
The AAT4670 dual channel load switch, implement-
ed 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 combina-
tion; one supply is not required to be the higher volt-
age. Internally, the power supply for the control cir-
cuitry 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 microsec-
ond, which eases requirements on the input capaci-
tors. With such fast transient response time, the
upstream power supply rail is naturally isolated from
the protected port. The AAT4670 is internally pro-
tected from thermal damage by an over temperature
detection circuit. If a high ambient temperature or an
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 uni-
form at high temperatures, and therefore, as a pre-
caution, 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 condi-
tion is reported by both FAULT outputs. A three mil-
lisecond blanking interval prevents false reporting
during the charging of a capacitive load, which typi-
cally occurs during device turn-on, but may also
occur during a port hot plug-in event.
The AAT4670 is ideally suited for protection of periph-
eral ports such as USB, PS2 and parallel ports.
Functional Block Diagram
INB
INA
OUTA
EN
FAULTB
Slew
Rate
I
LIM
OTMP
UVLO
Slew
Rate
I
LIM
UVLO
OUTB
FAULTA
GND
AAT4670
Dual-Input, Dual-Output Load Switches
4670.2002.1.0.92
7
Applications Information
Input Capacitor
The input capacitors, C
INA
and C
INB
, 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 capaci-
tor can dramatically reduce the voltage transient
seen by the power supply and other circuitry
upstream from the AAT4670. C
IN
should be located
as close to the device V
IN
pin as practically possible.
Ceramic, tantalum or aluminum electrolytic capaci-
tors may be selected for C
IN
. There is no specific
capacitor ESR requirement for C
IN
. However, for
higher current operation, ceramic capacitors are rec-
ommended for C
IN
due to their inherent capability
over tantalum capacitors to withstand input current
surges from low impedance sources such as batter-
ies in portable devices.
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.
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 tempera-
ture circuits in any combination are active for more
than approximately three milliseconds, the associ-
ated FAULT flag is pulled to ground through
approximately 100
. Removal of voltage or cur-
rent transients of less than three milliseconds pre-
vents capacitive loads connected to either
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.
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 appli-
cations, 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.
T
J(MAX)
= I
MAX
2
R
DS(ON)
(MAX)
R
JA
+ T
A
(MAX)
In Equation 1, I
MAX
is the maximum current
required by the load. R
DS(ON)
(MAX) is the maxi-
mum rated R
DS(ON)
of the AAT4670 at high temper-
ature. R
JA
is the thermal resistance between the
AAT4670 die and the board onto which it is mount-
ed. T
A
(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 I
MAX
; Equation 2.
I
MAX
=
T
SD
(MIN) - T
A
(MAX)
R
DS(ON)
(MAX)
R
JA
T
SD
(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 oper-
ate in 50C environments, the PCB operates at
temperatures as high as 85C. The application is
sealed and its PCB is small, causing R
JA
to be
approximately 120C/W. Using Equation 2,
I
MAX
=
115 - 85
= 1.25 A
160m
120
To prevent thermal limiting, the operating load cur-
rent 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 cur-
rent limit threshold is allowed.
AAT4670
Dual-Input, Dual-Output Load Switches
8
4670.2002.1.0.92
Timing Diagram
Ordering Information
Package
Marking
Part Number
Bulk
Tape and Reel
SOP-8
AAT4670IAS-B1
AAT4670IAS-T1
TSSOP-8
AAT4670IHS-B1
AAT4670IHS-T1
MSOP-8
AAT4670IKS-B1
AAT4670IKS-T1
EN
OUT
t1
t2
t3
t4
Package Information
SOP-8
E
b
e
H
D
A1
A
A2
7 (4x)
c
L
y
AAT4670
Dual-Input, Dual-Output Load Switches
4670.2002.1.0.92
9
Dim
Millimeters
Inches
Min
Max
Min
Max
A
1.35
1.75
0.053
0.069
A1
0.10
0.25
0.004
0.010
A2
1.45
0.057
B
0.33
0.51
0.013
0.020
C
0.19
0.25
0.007
0.010
D
4.80
5.00
0.189
0.197
E
3.80
4.00
0.150
0.157
e
1.27
0.050
H
5.80
6.20
0.228
0.244
L
0.40
1.27
0.016
0.050
Y
0.00
0.10
0.000
0.004
1
0
8
0
8
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.
TSSOP-8
A1
b
e
E
A
A2
E1
DETAIL A
R
L1
L
0.20
D
R1
2
E
1
DETAIL A
AAT4670
Dual-Input, Dual-Output Load Switches
10
4670.2002.1.0.92
Dim
Millimeters
Inches
Min
Max
Min
Max
A
1.05
1.20
0.041
0.047
A1
0.05
0.15
0.002
0.006
A2
-
1.05
-
0.041
b
0.25
0.30
0.010
0.012
c
0.127
0.005
D-8
2.90
3.10
0.114
0.122
D-28
9.60
9.80
0.378
0.386
E
4.30
4.50
0.170
0.177
E1
6.20
6.60
0.244
0.260
e
0.65 BSC
0.025 BSC
L
0.50
0.70
0.20
0.028
L1
1.0
0.039
R
0.09
-
0.004
-
R1
0.09
-
0.004
-
1
0
8
0
8
2
12
MSOP-8
E
E1
D
PIN 1
e1 t1
e1
A
L1
L
C
GAUGE PLANE
A1
A2
e
b
t1
t
(1)
AAT4670
Dual-Input, Dual-Output Load Switches
4670.2002.1.0.92
11
Dim
Millimeters
Inches
Min
Max
Min
Max
A
0.08
1.10
0.003
0.043
A1
0.00
0.15
0.000
0.005
A2
0.75
0.95
0.029
0.037
b
0.22
0.38
0.008
0.014
C
0.08
0.23
0.003
0.009
D
2.90
3.10
0.114
0.122
E
4.80
5.00
0.188
0.196
E1
2.90
3.10
0.114
0.122
e
0.65 BSC
0.025 BSC
e1
1.95 BSC
0.076 BSC
L
0.40
0.80
0.015
0.031
L1
0.95 REF
0.037 REF
L2
0.254 BSC
0.010 BSC
0
8
0
8
2
5
15
5
15
Note:
1. PACKAGE BODY SIZES EXCLUDE MOLD FLASH
PROTRUSIONS OR GATE BURRS.
2. TOLERANCE 0.1000mm (4mil) UNLESS OTHER-
WISE SPECIFIED
3. COPLANARITY: 0.1000mm
4. DIMENSION L IS MEASURED IN GAGE PLANE.
5. CONTROLLING DIMENSION IS MILLIMETER,
CONVERTED INCH DIMENSIONS ARE NOT NECES-
SARILY EXACT.
AAT4670
Dual-Input, Dual-Output Load Switches
12
4670.2002.1.0.92
Advanced Analogic Technologies, Inc.
1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086
Phone (408) 524-9684
Fax (408) 524-9689
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