AAT4285 [ANALOGICTECH]
12V Slew Rate Controlled Load Switch; 12V压摆率受控负载开关
| 型号： | AAT4285 |
| 厂家： | 
ADVANCED ANALOGIC TECHNOLOGIES |
| 描述： | 12V Slew Rate Controlled Load Switch |
| 文件： | 总11页 (文件大小：322K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
AAT4285
12V Slew Rate Controlled Load Switch
™
SmartSwitch
General Description
Features
The AAT4285 SmartSwitch is a P-channel MOSFET
power switch designed for high-side load switching
applications. The MOSFET operates from a 3.0V to
13.2V input range making it ideal for applications in
single or dual cell Lithium-Ion battery systems. The
•
•
VIN Range: 3.0V to 13.2V
Low RDS(ON)
— 240mΩ typical @ 12V
— 310mΩ Typical at 5V
100µs Slew Rate Turn-on Time
Fast Shutdown Load Discharge
Low Quiescent Current
•
•
•
device has a typical RDS(ON) of 240mΩ at 12V, allow-
ing a low forward voltage drop and high current han-
dling capability. The device is a slew rate limited turn-
on load switch and is functionally compatible with the
AAT4250 and AAT4280 products, while offering a
high operating voltage. The AAT4285 features fast
load switch turn-on capability of 100µs and offers a
shutdown load discharge circuit to rapidly turn off a
load circuit when the switch is disabled. The quies-
cent supply current is very low, typically 25µA.
— Typically 25µA
— 1µA Maximum in Shutdown
TTL/CMOS Input Logic Level
Temperature Range: -40°C to +85°C
8-pin SC70JW Package
•
•
•
Applications
The AAT4285 is available in a Pb-free, 8-pin
SC70JW package and is specified over the -40°C
to +85°C temperature range.
•
•
•
•
2 Cell Lithium-Ion Batteries
Camcorders
Handheld Test Equipment
Load Switching
Typical Application
VIN
IN
OUT
VOUT
AAT4285
IN
CIN
COUT
0.1µF
ON/OFF
ON
1µF
GND × 4
GND
GND
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AAT4285
12V Slew Rate Controlled Load Switch
Pin Descriptions
Pin #
Symbol
Function
1,2
3
4
IN
OUT
ON/OFF
P-channel MOSFET source. Bypass to ground through a 1µF capacitor.
P-channel MOSFET drain connection. Bypass to ground through a 0.1µF capacitor.
Active high enable input. A logic low turns the switch off and the device consumes
less than 1µA of current. Logic high resumes normal operation.
Ground connection
5, 6, 7, 8
GND
Pin Configuration
SC70JW-8
(Top View)
8
7
6
5
1
2
3
4
GND
GND
GND
GND
IN
IN
OUT
ON/OFF
2
4285.2007.04.1.0
AAT4285
12V Slew Rate Controlled Load Switch
1
Absolute Maximum Ratings
Symbol
Description
Value
Units
VIN
VON
VOUT
IMAX
IDM
IN to GND
ON/OFF to GND
OUT to GND
Maximum Continuous Switch Current
Maximum Pulsed Current
-0.3 to 14
-0.3 to 14
-0.3 to VIN + 0.3
1.7
V
V
V
A
A
3.4
TJ
Operating Junction Temperature Range
-40 to 150
°C
2
Thermal Characteristics
Symbol
Description
Value
Units
θJA
PD
Thermal Resistance
Maximum Power Dissipation
140
714
°C/W
mW
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
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AAT4285
12V Slew Rate Controlled Load Switch
1
Electrical Characteristics
VIN = 12V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol Description
Conditions
Min Typ Max Units
VIN
VUVLO
VUVLO(hys)
IQ
IQ(OFF)
ISHD
Operation Voltage
3.0
13.2
3.0
V
V
V
µA
µA
µA
Under-Voltage Lockout
Under-Voltage Lockout Hysteresis
Quiescent Current
Off Supply Current
Off Switch Current
2.7
250
25
ON/OFF = Active, IOUT = 0
ON/OFF = Inactive, OUT = Open
ON/OFF = GND, VOUT = 0
VIN = 12V
VIN = 5V
VIN = 3.3V
50
1.0
1.0
400
500
0.1
240
310
380
RDS(ON)
On Resistance
mΩ
On Resistance Temperature
Coefficient
TCRRDS
2800
ppm/°C
2
TD(ON)
TON
TD(OFF)
Output Turn-On Delay Time
RLOAD = 20Ω, TA = 25°C
RLOAD = 20Ω, TA = 25°C
RLOAD = 20Ω, TA = 25°C
20
100
1
40
250
10
µs
µs
µs
2
Turn-On Rise Time
2
Output Turn-Off Delay Time
Output Pull-Down Resistance
During OFF
ON/OFF Input Logic Low Voltage VIN = 3V to 13V
ON/OFF Input Logic High Voltage VIN = 3V to 13V
RPD
ON/OFF Inactive, TA = 25°C
520
800
0.4
Ω
VON(L)
VON(H)
ION
V
V
µA
1.6
-1.0
ON/OFF Leakage Current
VON/OFF = 13V
1.0
1. The AAT4285 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. Contact factory for other turn-on and delay options.
4
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AAT4285
12V Slew Rate Controlled Load Switch
Typical Characteristics
Quiescent Current vs. Temperature
Quiescent Current vs. Input Voltage
30
25
35
30
25
20
15
10
5
20
VIN = 12V
VIN = 5V
VIN = 4.2V
15
10
5
VIN = 3.3V
0
0
-40
-15
10
35
60
85
0
2
4
6
8
10
12
14
Temperature (°°C)
Input Voltage (V)
RDS(ON) vs. Temperature
RDS(ON) vs. Input Voltage
500
420
450
400
350
300
250
200
150
100
VIN = 4.2V
380
340
300
260
220
VIN = 3.3V
0.1A
0.5A
2A
1A
VIN = 12V
VIN = 5V
-40
-15
10
35
60
85
3
4
5
6
7
8
9
10
11
12
Temperature (°°C)
Input Voltage (V)
ON/OFF Threshold Low vs. Input Voltage
ON/OFF Threshold High vs. Input Voltage
1.05
0.95
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
-40°C
-40°C
25°C
85°C
85°C
25°C
3
5
7
9
11
13
3
5
7
9
11
13
Input Voltage (V)
Input Voltage (V)
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AAT4285
12V Slew Rate Controlled Load Switch
Typical Characteristics
Output Pull-Down Resistance
vs. Temperature
Turn-On
(VIN = 12V; 600mA Load)
800
750
700
650
600
550
500
450
400
ON/OFF
(5V/div)
VIN = 4.2V
VIN = 3.3V
VOUT
(5V/div)
IOUT
(500mA/div)
VIN = 12V
VIN = 5V
-40
-15
10
35
60
85
Temperature (°C)
Time (25µs/div)
Turn-Off
(VIN = 12V; 600mA Load)
ON/OFF
(5V/div)
VOUT
(5V/div)
IOUT
(500mA/div)
Time (10µs/div)
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AAT4285
12V Slew Rate Controlled Load Switch
Functional Block Diagram
IN
OUT
Under-
Voltage
Lockout
Turn-On
Slew Rate
Control
Level
Shift
ON/OFF
GND GND GND GND
the MOSFET is turned on, allowing the AAT4285 to
Functional Description
operate with a small input capacitor, or no input
capacitor at all. During slewing, the current ramps
linearly until it reaches the level required for the
output load condition. The proprietary control
method works by careful control and monitoring of
the MOSFET gate voltage. When the device is
switched ON, the gate voltage is quickly increased
to the threshold level of the MOSFET. Once at this
level, the current begins to slew as the gate voltage
is slowly increased until the MOSFET becomes
fully enhanced. Once it has reached this point, the
gate is quickly increased to the full input voltage
and RDS(ON) is minimized.
The AAT4285 is a slew rate controlled P-channel
MOSFET power switch designed for high-side load
switching applications. The device operates with
input voltages ranging from 3.0V to 13.2V, making
it ideal for single- or multi-cell battery-powered
applications. In cases where the input voltage
drops below 3.0V, the AAT4285 MOSFET is pro-
tected from entering the saturated region of opera-
tion by automatically shutting down. In addition, the
TTL compatible ON/OFF pin makes the AAT4285
an ideal level-shifted load switch. The slew rate
controlling feature eliminates inrush current when
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AAT4285
12V Slew Rate Controlled Load Switch
itor is highly recommended. A larger value of CIN
with respect to COUT will affect a slower CIN decay
rate during shutdown, thus preventing VOUT from
exceeding VIN. In applications where there is a
greater danger of VOUT exceeding VIN for extended
periods of time, it is recommended to place a
Schottky diode from IN to OUT (connecting the
cathode to IN and anode to OUT). The Schottky
diode forward voltage should be less than 0.45V.
Applications Information
Input Capacitor
A 1µF or larger capacitor is typically recommended
for CIN in most applications. A CIN capacitor is not
required for basic operation. However, CIN is useful
in preventing load transients from affecting
upstream circuits. CIN should be located as close to
the device VIN pin as practically possible.
Ceramic, tantalum, or aluminum electrolytic capac-
itors 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 capabil-
ity over tantalum capacitors to withstand input cur-
rent surges from low impedance sources, such as
batteries in portable devices.
Thermal Considerations and High
Output Current Applications
The AAT4285 is designed to deliver a continuous
output load current. The limiting characteristic for
maximum safe operating output load current is
package power dissipation. In order to obtain high
operating currents, careful device layout and circuit
operating conditions need to be taken into account.
The following discussions will assume the load
switch is mounted on a printed circuit board utilizing
the minimum recommended footprint, as stated in
the Layout Considerations section of this datasheet.
Output Capacitor
For proper slew operation, a 0.1µF capacitor or
greater between OUT and GND is recommended.
The output capacitor has no specific capacitor type
or ESR requirement. If desired, COUT may be
increased without limit to accommodate any load
transient condition without adversely affecting the
device turn-on slew rate time.
At any given ambient temperature (TA), the maxi-
mum package power dissipation can be deter-
mined by the following equation:
TJ(MAX) - TA
PD(MAX)
=
θJA
Enable Function
The AAT4285 features an enable / disable function.
This pin (ON/OFF) is compatible with both TTL and
CMOS logic.
Constants for the AAT4285 are maximum junction
temperature, TJ(MAX) = 125°C, and package thermal
resistance, θJA = 140°C/W. Worst case conditions
are calculated at the maximum operating tempera-
ture where TA = 85°C. Typical conditions are calcu-
lated under normal ambient conditions where TA =
25°C. At TA = 85°C, PD(MAX) = 286mW. At TA =
25°C, PD(MAX) = 714mW.
Reverse Output-to-Input Voltage
Conditions and Protection
Under normal operating conditions, a parasitic diode
exists between the output and input of the load
switch. The input voltage should always remain
greater than the output load voltage, maintaining a
reverse bias on the internal parasitic diode.
Conditions where VOUT might exceed VIN should be
avoided since this would forward bias the internal
parasitic diode and allow excessive current flow into
the OUT pin and possibly damage the load switch.
The maximum continuous output current for the
AAT4285 is a function of the package power dissipa-
tion and the RDS of the MOSFET at TJ(MAX). The max-
imum RDS of the MOSFET at TJ(MAX) is calculated by
increasing the maximum room temperature RDS by
the RDS temperature coefficient. The temperature
coefficient (TCRRDS) is 2800ppm/°C. Therefore,
In applications where there is a possibility of VOUT
exceeding VIN for brief periods of time during nor-
mal operation, the use of a larger value CIN capac-
MAX RDS125°C = RDS25°C · (1 + TCRRDS · ΔT)
MAX RDS125°C = 240mΩ · (1 + 0.0028 · (125°C - 25°C))
= 307mΩ
8
4285.2007.04.1.0
AAT4285
12V Slew Rate Controlled Load Switch
For maximum current, refer to the following equation:
PD(MAX)
The power dissipation for a 100mA load is calculat-
ed as follows:
IOUT(MAX)
<
PD(MAX) = IOUT2 · RDS
RDS
PD(100mA) = (100mA)2 · 307mΩ
PD(100mA) = 3.07mW
For example, if VIN = 12V, RDS(MAX) = 307mΩ
and
TA = 25°C, IOUT(MAX) = 1.53A. If the output load cur-
rent were to exceed 1.53A or if the ambient tem-
perature were to increase, the internal die temper-
ature would increase, and the device would be
damaged. Higher peak currents can be obtained
with the AAT4285. To accomplish this, the device
thermal resistance must be reduced by increasing
the heat sink area or by operating the load switch
in a duty cycled manner.
PD(90%D/C) = %DC · PD(100mA)
PD(90%D/C) = 0.90 · 3.07mW
PD(90%D/C) = 2.76mW
The power dissipation for 100mA load at 90% duty
cycle is 2.76mW. Now the power dissipation for the
remaining 10% of the duty cycle at 2A is calculated:
PD(MAX) = IOUT2 · RDS
PD(2A) = (2A)2 · 307mΩ
PD(2A) = 1.23W
High Peak Output Current Applications
Some applications require the load switch to operate
at a continuous nominal current level with short
duration, high-current peaks. The duty cycle for both
output current levels must be taken into account. To
do so, first calculate the power dissipation at the
nominal continuous current level, and then add in
the additional power dissipation due to the short
duration, high-current peak scaled by the duty factor.
PD(10%D/C) = %DC · PD(2A)
PD(10%D/C) = 0.10 · 1.23mW
PD(10%D/C) = 123mW
The power dissipation for 2A load at 10% duty
cycle is 123mW. Finally, the two power figures are
summed to determine the total true power dissipa-
tion under the varied load.
For example, a 12V system using an AAT4285
operates at a continuous 100mA load current level
and has short 2A current peaks.
The current peak occurs for 500µs out of a 5ms
period.
PD(TOTAL) = PD(100mA) + PD(2A)
PD(TOTAL) = 2.76mW + 123mW
First, the current duty cycle is calculated:
PD(TOTAL) = 125.76mW
⎛ x ⎞ ⎛ 500μs⎞
100
The maximum power dissipation for the AAT4285
operating at an ambient temperature of 85°C is
286mW. The device in this example will have a total
power dissipation of 123mW. This is well within the
thermal limits for safe operation of the device; in fact,
at 85°C, the AAT4285 will handle a 2A pulse for up
to 23% duty cycle. At lower ambient temperatures,
the duty cycle can be further increased.
% Peak Duty Cycle =
=
⎝
⎠
⎝
⎠
5.0ms
% Peak Duty Cycle = 10%
The load current is 100mA for 90% of the 5ms peri-
od and 2A for 10% of the period.
De-rated for temperature:
Printed Circuit Board Layout
Recommendations
240mΩ · (1 + 0.0028 · (125°C - 25°C)) = 307mΩ
For proper thermal management and to take
advantage of the low RDS(ON) of the AAT4285, a few
circuit board layout rules should be followed: VIN
4285.2007.04.1.0
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AAT4285
12V Slew Rate Controlled Load Switch
and VOUT should be routed using wider than normal
traces, and GND should be connected to a ground
plane. To maximize package thermal dissipation
and power handling capacity of the AAT4285
SC70JW-8 package, the ground plane area con-
nected to the ground pins should be made as large
as possible. For best performance, CIN and COUT
should be placed close to the package pins.
Evaluation Board Layout
The AAT4285 evaluation board layout follows the
printed circuit board layout recommendations and
can be used for good application guide. Refer to
Figures 1 through 3.
Note: Board layout shown is not to scale.
Figure 1: AAT4285 Evaluation Board
Component Side Layout and Silk Screen.
Figure 2: AAT4285 Evaluation Board Solder
Side Layout.
VOUT
VIN
1
8
IN
IN
OUT
EN
GND
2
7
C2
0.1μF
GND
GND
GND
3
6
5
4
R1
100K
AAT4285
C1
1μF
JP1
ON/OFF
C1 1μF X7R 16V 0805 GRM21BR71C105KA01
(C1 1μF X5R 16V 0603 GRM188R61C105KA93)
C2 0.1μF X5R 16V 0805 GRM219R71C104KA01
(C2 0.1μF X7R 16V 0603 GRM188R71C104KA01)
Figure 3: AAT4285 Evaluation Board Circuit Schematic Diagram.
10
4285.2007.04.1.0
AAT4285
12V Slew Rate Controlled Load Switch
Ordering Information
1
2
Package
Marking
Part Number (Tape and Reel)
SC70JW-8
UAXYY
AAT4285IJS-3-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
SC70JW-8
0.50 BSC 0.50 BSC 0.50 BSC
0.225 0.075
2.00 0.20
0.048REF
0.100
0.45 0.10
4° 4°
7° 3°
2.10 0.30
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
© Advanced Analogic Technologies, Inc.
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 with-
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830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
4285.2007.04.1.0
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