SmartSwitch
TM
AAT4612
Current Limited Load Switch
Preliminary
Information
4612.2002.1.0.9
1
General Description
The AAT4612 SmartSwitchTM is a member of
AnalogicTech's Application Specific Power MOS-
FETTM (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 both 3V and 5V systems. An integrated cur-
rent-limiting circuit protects the input supply from large
currents which potentially cause the supply to fall out
of regulation. In addition, the AAT4612 thermal over-
load protection limits power dissipation and junction
temperatures associated with prolonged periods of
operation in current limit. Due to its low R
DS(ON)
, the
AAT4612 can be used to control loads that require up
to 1A even while operating at high ambient tempera-
tures. The ultra fast current-limit response to a sud-
den short circuit is a mere 500ns which reduces the
requirements of local supply bypassing. Quiescent
current is a low 1
0A and in shutdown mode, the
supply current decreases to less than 1A.
The AAT4612 is available in a 5-pin SOT23, and an
8-pin SC70JW specified over a -40 to 85C temper-
ature 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 ver-
sions with fixed current limit (AAT4626, AAT4670).
Features
2.
4V to 5.5V Input voltage range
1A current limit trip threshold
Fast transient response:
<1s response to short circuit
Low quiescent current
1
0A typ
1A max with Switch off
100m
typical R
DS(ON)
Undervoltage Lockout
Thermal Shutdown
Temp range -40 to 85C
4kV ESD Rating
5-pin SOT23 package
8-pin SC70JW package
Applications
Peripheral ports
Notebook computers
Personal communication devices
Hot swap supplies
Typical Application
AAT4612
SOT23
ON
IN
OUT
GND
ON
INPUT
GND
GND
C
IN
1
F
C
OUT
0.47
F
V
CC
1
2
5
4
Pin Descriptions
Pin Configuration
SOT23-5
SC70JW-8
OUT
IN
IN
1
2
GND
GND
GND
GND
ON
1
2
3
4
8
7
6
5
1
2
3
ON
NC
IN
4
5
GND
OUT
Pin #
SOT23-5
SC70JW
Symbol
Function
1
2
OUT
P-channel MOSFET drain
2
5, 6, 7, 8
GND
Ground connection
3
NC
Not internally connected
4
1
ON
Active low enable Input
5
3, 4
IN
P-channel MOSFET source
AAT4612
Current Limited Load Switch
2
4612.2002.1.0.9
AAT4612
Current Limited Load Switch
4612.2002.1.0.9
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
= -40 to 85C unless otherwise noted. Typical values
are at T
A
=25C;
bold values denote full temperature range)
Note 3: For V
IN
outside this range consult typical ON threshold curve.
Symbol
Description
Conditions
Min
Typ
Max
Units
V
IN
Operation Voltage
2.
4
5.5
V
I
Q
Quiescent Current
V
IN
= 5V, ON = active, I
OUT
= 0
1
0
20
A
I
Q(OFF)
Off Supply Current
ON = inactive, V
IN
= 5.5V
1
A
I
SD(OFF)
Off Switch Current
ON = inactive, V
IN
= 5.5V, V
OUT
= 0
0.1
1
A
V
UVLO
Undervoltage Lockout
V
IN
falling
1.
9
V
V
UVLO(hys)
Undervoltage Lockout Hysteresis
0.3
V
R
DS(ON)
On-Resistance
V
IN
=5.0V, T
A
= 25C
100
150
m
V
IN
=3.0V, T
A
= 25C
140
180
I
LIM
Current Limit
V
OUT
= V
IN
- 0.5V
1
1.5
2.0
A
V
ON(L)
ON Input Low Voltage
V
IN
= 2.7V to 5.5V
3
0.8
V
V
ON(H)
ON Input High Voltage
V
IN
= 2.7V
4.2V
2.0
V
V
IN
= > 4.2V to 5.
0V
3
2.4
I
ON(SINK)
ON Input leakage
V
ON
= 5.5V
0.01
1
A
t
RESP
Current Loop Response
V
IN
= 5V
500
ns
T
OFF
Turn-Off Time
V
IN
= 5V, R
L
= 10
2.5
s
T
ON
Turn-On Time
V
IN
= 5V, R
L
= 10
1
s
OTMP
Over Temperature Shutdown
125
C
Symbol
Description
Value
Units
JA
Maximum Thermal Resistance
2
(SOT23-5, SC70JW-8)
150
C/W
P
D
Maximum Power Dissipation
2
(SOT23-5, SC70JW-8)
667
mW
Symbol
Description
Value
Units
V
IN
IN to GND
-0.3 to 6
V
V
ON
ON to GND
-0.3 to 6
V
V
OUT
OUT 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
Off-Switch Current vs. Temperature
0.00
0.01
0.10
1.00
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
Off-Switch Current (
A)
Off-Supply Current vs. Temperature
0.00
0.01
0.10
1.00
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
Off-Supply Current (
A)
R
DS(ON)
vs. Temperature
0
20
40
60
80
100
120
140
160
180
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
R
DS(ON)
(m
)
V
IN
=5V
V
IN
=3V
Current Limit vs. V
OUT
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0
1
2
3
4
5
V
OUT
(V)
Current Limit (A)
Quiescent Current vs. Input Voltage
0
5
10
15
20
0
1
2
3
4
5
6
IN (V)
Quiescent Current (
A)
Quiescent Current vs. Temperature
0
5
10
15
20
-40
-20
0
20
40
60
80
100
120
Temperature (
C)
Quiescent Current (
A)
AAT4612
Current Limited Load Switch
4
4612.2002.1.0.9
Typical Characteristics
ON Threshold vs. V
IN
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2
2.5
3
3.5
4
4.5
5
5.5
V
IN
(V)
ON Threshold (V)
V
ON(H)
V
ON(L)
Thermal Shutdown Response
Time (50ms/div)
Output Voltage (5V/div)
Output Current (1A/div)
Short Circuit through 0.3
0.0
1.0
2.0
3.0
4.0
5.0
6.0
-1
0
1
2
3
4
5
Time (
s)
Input and Output (V)
0
2
4
6
8
10
12
Output (A)
Input Voltage
Output Current
Output Voltage
Turn-Off
-1
0
1
2
3
4
5
6
-5
0
5
10
15
20
Time (
s)
Voltage (V)
R
L
=10
, C
L
=0.47
F
ON
OUT
Turn-On
R
L
=10
, C
L
=0.47
F
-1
0
1
2
3
4
5
6
-0.5
0.0
0.5
1.0
1.5
2.0
Time (
s)
Voltage (V)
ON
OUT
AAT4612
Current Limited Load Switch
4612.2002.1.0.9
5
Functional Description
The AAT4612 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 frac-
tion of a micro second and instantly resets to low
impedance once the short circuit condition is
removed. The AAT4612 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 AAT4612 operates with input volt-
ages 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 AAT4612
MOSFET is protected from entering the saturated
region of operation by being automatically shut
down by an under voltage lockout circuit.
The AAT4612 is ideally suited for protection of
peripheral ports such as USB, RS232 and parallel
ports.
AAT4612
Current Limited Load Switch
6
4612.2002.1.0.9
Functional Block Diagram
IN
OUT
ON
GND
Under-Voltage
Lockout
Over-Temp
Protection
Current
Limit
Applications Information
Input Capacitor
The input capacitor, C
IN
protects the power supply
from current transients generated by the load
attached to the AAT4612. When a short circuit is
suddenly applied to the output of the AAT4612, a
large current, limited only by the R
DS(ON)
of the
MOSFET, will flow for less than 1s before the cur-
rent limit circuitry activates. (See characteristic
curve "Short Circuit Through 0.3
.") In this event,
a moderately sized C
IN
will dramatically reduce the
voltage transient seen by the power supply and by
other circuitry upstream from the AAT4612. The
extremely fast short circuit response time of the
AAT4612 reduces the size requirement of C
IN
.
C
IN
should be located as close to the device V
IN
pin
as practically possible. Ceramic, tantalum or alu-
minum electrolytic capacitors are appropriate for
C
IN
. There is no specific capacitor ESR require-
ment for C
IN
. However, for higher current opera-
tion, ceramic capacitors are recommended for C
IN
due to their inherent capability over tantalum
capacitors to withstand input current surges from
low impedance sources such as batteries in
portable devices.
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 AAT4612 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
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 AAT4612 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.
When switching the AAT4612 on into a capacitive
load, the AAT4612 will charge the output capacitive
load at a rate no greater than the current limit setting.
Attaching Loads
Capacitive loads attached to an enabled AAT4612
will charge at a rate no greater than the current limit
setting.
Thermal Considerations
Since the AAT4612 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 with-
out 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 AAT4612 at high temper-
ature. R
JA
is the thermal resistance between the
AAT4612 die and the board onto which it is mount-
ed. T
A
(MAX) is the maximum temperature that the
PCB under the AAT4612 would be if the AAT4612
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 AAT4612 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 150 C/W. Using Equation 2,
I
MAX
=
((115 - 85)
= 1 A
(188m
150))
The AAT4612 is safe to operate at the maximum
current level of 1A at 85C.
AAT4612
Current Limited Load Switch
4612.2002.1.0.9
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AAT4612
Current Limited Load Switch
8
4612.2002.1.0.9
Ordering Information
Package Information
SOT23-5
E
A
A1
c
b
D
e
S1
L
I
H
A2
S
Package
Marking
Part Number
Bulk
Tape and Reel
SOT23-5
N/A
AAT4612IGV-T1
SC70JW-8
N/A
AAT4612IJS-T1
Dim
Millimeters
Inches
Min
Max
Min
Max
A
1.00
1.30
0.039
0.051
A1
0.00
0.10
0.000
0.004
A2
0.70
0.90
0.028
0.035
b
0.35
0.50
0.014
0.020
c
0.10
0.25
0.004
0.010
D
2.70
3.10
0.106
0.122
E
1.40
1.80
0.055
0.071
e
1.90
0.075
H
2.60
3.00
0.102
0.118
L
0.37
0.015
S
0.45
0.55
0.018
0.022
S1
0.85
1.05
0.033
0.041
1
9
1
9
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.
AAT4612
Current Limited Load Switch
4612.2002.1.0.9
9
SC70JW-8
1
D
A
A2
b
E
e
e
e
L
E1
A1
c
0.048REF
Dim
Millimeters
Inches
Min
Max
Min
Max
E
2.10 BSC
0.083 BSC
E1
1.75
2.00
0.069
0.079
L
0.23
0.40
0.009
0.016
A
1.10
0.043
A1
0
0.10
0.004
A2
0.70
1.00
0.028
0.039
D
2.00 BSC
0.079 BSC
e
0.50 BSC
0.020 BSC
b
0.15
0.30
0.006
0.012
c
0.10
0.20
0.004
0.008
0
8
0
8
1
4
10
4
10
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AAT4612
Current Limited Load Switch
10
4612.2002.1.0.9
Advanced Analogic Technologies, Inc.
1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086
Phone (408) 524-9684
Fax (408) 524-9689
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