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AAT4280A
Slew Rate Controlled Load Switch General Description
The AAT4280A SmartSwitchTM is a member of AnalogicTech's Application Specific Power MOSFETTM (ASPMTM) product family. The AAT4280A is a P-channel MOSFET power switch designed for high-side load-switching applications. The device has a typical RDS(ON) of 80m, allowing increased load switch power handling capacity and is available in three different versions with flexible turn-on and turn-off characteristics -- from very fast to slew rate limited. The standard AAT4280A (-1) version has a slew rate limited turn-on load switch and is functionally compatible with the AAT4250 device, while offering superior RDS(ON) characteristics. The AAT4280A (-2) version features fast load switch turn-on capabilities, typically less than 500ns turnon and 3s turn-off times. The AAT4280A (-3) variation offers a shutdown load discharge circuit to rapidly turn off a load circuit when the switch is disabled. All AAT4280A load switch versions operate with an input voltage ranging from 1.5V to 5.5V, making them ideal for both 3V and 5V systems. Input logic levels are TTL and 2.5V to 5V CMOS compatible. The quiescent supply current is very low, typically 25nA. The AAT4280A is available in an 8-pin SC70JW package and is specified over the -40C to +85C temperature range.
Features
* * *
SmartSwitchTM
* * * * * *
1.5V to 5.5V Input Voltage Range Very Low RDS(ON), Typically 80m (5V) Slew Rate Limited Turn-On Time Options -- 1ms -- 0.5s -- 100s Fast Shutdown Load Discharge Option Low Quiescent Current -- 25nA (typ) TTL/CMOS Input Logic Level Temperature Range: -40C to +85C 4kV ESD Rating 8-Pin SC70JW Package
Applications
* * * * * * Cellular Telephones Digital Still Cameras Hot Swap Supplies Notebook Computers Personal Communication Devices Personal Digital Assistants (PDAs)
Typical Application
V IN
IN IN C IN 1F ON
OUT
V OUT
AAT4280A
GND GND C OUT 0.1F
ON/OFF
GND
GND
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AAT4280A
Slew Rate Controlled Load Switch Pin Descriptions
Pin #
1, 5, 6, 7, 8 2 3 4
Symbol
IN OUT ON/OFF GND
Function
The pin is the input to the P-channel MOSFET source. Bypass to ground through a 1.0F capacitor. The pin is the P-channel MOSFET drain connection. Bypass to ground through a 0.1F capacitor. Enable input. Ground connection.
Pin Configuration
SC70JW-8 (Top View)
IN OUT ON/OFF GND
1 2 3 4
8 7 6 5
IN IN IN IN
Selector Guide
Slew Rate (typ)
1mS 0.5S 100S
Part Number
AAT4280A-1 AAT4280A-2 AAT4280A-3
Active Pull Down
Enable
Active High Active High Active High
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AAT4280A
Slew Rate Controlled Load Switch Absolute Maximum Ratings1
TA = 25C, unless otherwise noted. Symbol
VIN VON VOUT IMAX IDM TJ TLEAD VESD
Description
IN to GND ON/OFF to GND OUT to GND Maximum Continuous Switch Current Maximum Pulsed Current Operating Junction Temperature Range Maximum Soldering Temperature (at leads) ESD Rating2 - HBM IN 2.5V IN < 2.5V
Value
-0.3 to 6 -0.3 to 6 -0.3 to VIN+0.3 2.3 6 3 -40 to 150 300 4000
Units
V V V A A A C C V
Thermal Characteristics
Symbol
JA PD
Description
Thermal Resistance Power Dissipation3
3
Value
140 714
Units
C/W mW
Notes: 1. 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. 2. Human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin. 3. Mounted on an AAT4280A demo board in still 25C air.
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AAT4280A
Slew Rate Controlled Load Switch Electrical Characteristics
Unless otherwise noted, VIN = 5V, TA = -40C to +85C; typical values are at TA = 25C. Symbol Description
AAT4280A All Versions VIN Operation Voltage IQ Quiescent Current IQ(off) Off Supply Current ISD(off) Off Switch Current RDS(on) On-Resistance
Conditions
Min
1.5
Typ
Max
5.5 1 1 1 120 130 150 250 0.4
Units
V A A A
ON/OFF = Active ON/OFF = Inactive, OUT = Open ON/OFF = Inactive, VOUT = 0 VIN = 5V, TA = 25C VIN = 4.2V, TA = 25C VIN = 3V, TA = 25C VIN = 1.8V, TA = 25C VIN = 1.8V to 5.5V1 VIN = 2.7V to 4.2V VIN = 4.2V to 5.5V VIN = 1.5V to 2.7V VON/OFF = 5.5V VIN = 5V, RLOAD = 10, TA = 25C VIN = 5V, RLOAD = 10, TA = 25C VIN = 5V, RLOAD = 10, TA = 25C VIN = 5V, RLOAD = 10, TA = 25C VIN = 5V, RLOAD = 10, TA = 25C VIN = 5V, RLOAD = 10, TA = 25C VIN = 5V, VIN = 5V, VIN = 5V, ON/OFF RLOAD = 10, TA = 25C RLOAD = 10, TA = 25C RLOAD = 10, TA = 25C = Inactive, TA = 25C
TCRDS VIL VIH
On-Resistance Temperature Coefficient ON/OFF Input Logic Low Voltage ON/OFF Input Logic High Voltage
80 85 100 160 2800 2 2.4 1.4
m
ppm/C V V
ISINK ON/OFF Input Leakage AAT4280A-1 TD(ON) Output Turn-On Delay TON Output Turn-On Rise Time TD(OFF) Output Turn-Off Delay Time AAT4280A-2 TD(ON) Output Turn-On Delay TON Output Turn-On Rise Time TD(OFF) Output Turn-Off Delay Time AAT4280A-3 TD(ON) Output Turn-On Delay TON Output Turn-On Rise Time TD(OFF) Output Turn-Off Delay Time RPD Output Pull-Down Resistance During OFF
1 20 1000 4 0.5 0.5 4 20 100 4 150 40 1500 10 2 1 10 40 150 10 250
A S S S S S S S S S
Notes: 1. For VIN outside this range, consult typical ON/OFF threshold curve.
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AAT4280A
Slew Rate Controlled Load Switch Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25C. Quiescent Current vs. Temperature
50 190 40 170
RDS(ON) vs. VIN
2A 1A 500mA 100mA
RDS(ON) (m)
IQ (nA)
30 20 10 0 -40 -20 0 20 40 60 80 100
150 130 110 90 70 1.5 2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Temperature (C)
VIN (V)
RDS(ON) vs. Temperature
ON/OFF Threshold (V)
120 110 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 1.5 -40 -20 0 20 40 60 80 100 2.0
ON/OFF Threshold vs. VIN
RDS(ON) (m)
100 90 80 70 60 50 40
VIN=3V
VIH VIL
VIN=5V
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Temperature (C)
VIN (V)
Off Switch Current vs. Temperature
1.000
IOFFSW (A)
0.100
0.010
0.001 -40
-20
0
20
40
60
80
100
Temperature (C)
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AAT4280A
Slew Rate Controlled Load Switch Typical Characteristics--4280A-1
Unless otherwise noted, VIN = 5V, TA = 25C. AAT4280A-1 Turn-On
(VIN = 3V; RL = 6)
AAT4280A-1 Turn-On
(VIN = 5V; RL = 10)
ON/OFF (5V/div) VOUT (2V/div)
ON/OFF (5V/div)
VOUT (2V/div)
IIN (200mA/div)
IIN (200mA/div) Time (500s/div)
Time (500s/div)
AAT4280A-1 Turn-Off
(VIN = 3V; RL = 6)
AAT4280A-1 Turn-Off
(VIN = 5V; RL = 10)
ON/OFF (5V/div)
ON/OFF (5V/div)
VOUT (2V/div)
VOUT (2V/div)
IIN (200mA/div) Time (10s/div) Time (10s/div)
IIN (200mA/div)
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AAT4280A
Slew Rate Controlled Load Switch Typical Characteristics--4280A-2
Unless otherwise noted, VIN = 5V, TA = 25C. AAT4280A-2 Turn-On
(VIN = 3V; RIN = 6)
AAT4280A-2 Turn-On
(VIN = 5V; RL = 10)
ON/OFF (5V/div) VOUT (2V/div)
ON/OFF (5V/div)
VOUT (2V/div)
IIN (200mA/div) Time (5s/div)
IIN (200mA/div)
Time (5s/div)
AAT4280A-2 Turn-Off
(VIN = 3V; RL = 6)
AAT4280A-2 Turn-Off
(VIN = 5V; RL = 10)
ON/OFF (5V/div)
ON/OFF (5V/div)
VOUT (2V/div)
VOUT (2V/div)
IIN (200mA/div)
IIN (200mA/div) Time (5s/div)
Time (5s/div)
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AAT4280A
Slew Rate Controlled Load Switch Typical Characteristics--4280A-3
Unless otherwise noted, VIN = 5V, TA = 25C. AAT4280A-3 Turn-On
(VIN = 3V; RL = 6)
AAT4280A-3 Turn-On
(VIN = 5V; RL = 10)
ON/OFF (5V/div) VOUT (2V/div)
ON/OFF (5V/div)
VOUT (2V/div)
IIN (200mA/div)
IIN (200mA/div)
Time (50s/div)
Time (50s/div)
AAT4280A-3 Turn-Off
(VIN = 3V; RL = 6)
AAT4280A-3 Turn-Off
(VIN = 5V; RL = 10)
ON/OFF (5V/div)
ON/OFF (5V/div)
VOUT (2V/div)
VOUT (2V/div)
IIN (200mA/div) Time (5s/div) Time (5s/div)
IIN (200mA/div)
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AAT4280A
Slew Rate Controlled Load Switch Functional Block Diagram
IN OUT
Level Shift
Turn-On Slew Rate Control
*
ON/OFF
GND
*AAT4280A-3 only
Functional Description
The AAT4280A is a family of flexible P-channel MOSFET power switches designed for high-side load switching applications. There are three versions of the AAT4280A with different turn-on and turn-off characteristics to choose from, depending upon the specific requirements of an application. The first version, AAT4280A-1, has a moderate turn-on slew rate feature, which reduces in-rush current when the MOSFET is turned on. This function allows the load switch to be implemented with a small input capacitor, or no input capacitor at all. During turn-on slewing, the current ramps linearly until it reaches the level required for the output load condition. The proprietary turn-on current 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 second version, the AAT4280A-2, is a very fast switch intended for high-speed switching applications. This version has no turn-on slew rate control and no special output discharge features. The final switch version, the AAT4280A-3, has the addition of a minimized slew rate limited turn-on function and a shutdown output discharge circuit to rapidly turn off a load when the load switch is disabled through the ON/OFF pin. All versions of the AAT4280A operate with input voltages ranging from 1.5V to 5.5V. All versions of this device have extremely low operating current, making them ideal for battery-powered applications. The ON/OFF control pin is TTL compatible and will also function with 2.5V to 5V logic systems, making the AAT4280A an ideal level shifting loadswitch.
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AAT4280A
Slew Rate Controlled Load Switch Applications Information
Input Capacitor
Typically a 1F or larger capacitor is 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 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. operation, the use of a larger value CIN capacitor is highly recommended. A larger value of CIN with respect to COUT will effect 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 VIN to VOUT (connecting the cathode to VIN and anode to VOUT). The Schottky diode forward voltage should be less than 0.45V.
Thermal Considerations and High Output Current Applications
The AAT4280A 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. 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 AAT4280A 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. The maximum continuous output current for the AAT4280A is a function of the package power dissipation and the RDS of the MOSFET at TJ(MAX). The maximum RDS of the MOSFET at TJ(MAX) is calculated by increasing the maximum room temperature RDS by the RDS temperature coefficient. The temperature coefficient (TC) is 2800ppm/C. Therefore, MAX RDS125C = RDS25C x (1 + TC x T) MAX RDS125C = 120m x (1 + 0.0028 x (125C - 25C)) = 154m
Output Capacitor
For proper slew operation, a 0.1F capacitor or greater between VOUT 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.
Enable Function
The AAT4280A features an enable / disable function. This pin (ON/OFF) is compatible with both TTL or CMOS logic.
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 VOUT pin and possible damage to the load switch. In applications where there is a possibility of VOUT exceeding VIN for brief periods of time during normal
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AAT4280A
Slew Rate Controlled Load Switch
For maximum current, refer to the following equation: IOUT(MAX) < ( PD(MAX) / RDS)
1/2
For example, if VIN = 5V, RDS(MAX)=154m and TA = 25C, IOUT(MAX) = 2.3A. If the output load current were to exceed 2.3A or if the ambient temperature were to increase, the internal die temperature would increase and the device would be damaged. Higher peak currents can be obtained with the AAT4280A. 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 cycle manner.
reported for 5V can be scaled by the ratio seen in the chart to derive the RDS for a 4V VIN: 120m x 87m /80m = 130m. De-rated for temperature: 130m x (1 + .0028 x (125C -25C)) = 166m. The power dissipation for a 100mA load is calculated as follows: PD(MAX) = IOUT2 x RDS PD(100mA) = (100mA)2 x 166m PD(100mA) = 1.66mW PD(87.5%D/C) = %DC x PD(100mA) PD(87.5%D/C) = 0.875 x 1.66mW PD(87.5%D/C) = 1.45mW The power dissipation for 100mA load at 87.5% duty cycle is 1.45mW. Now the power dissipation for the remaining 12.5% of the duty cycle at 2A is calculated: PD(MAX) = IOUT2 x RDS PD(2A) = (2A)2 x 166m PD(2A) = 664mW PD(12.5%D/C) = %DC x PD(2A) PD(12.5%D/C) = 0.125 x 664mW PD(12.5%D/C) = 83mW The power dissipation for 2A load at 12.5% duty cycle is 83mW. Finally, the two power figures are summed to determine the total true power dissipation under the varied load: PD(total) = PD(100mA) + PD(2A) PD(total) = 1.45mW + 83mW PD(total) = 84.5mW The maximum power dissipation for the AAT4280A operating at an ambient temperature of 85C is 333mW. The device in this example will have a total power dissipation of 84.5mW. This is well within the thermal limits for safe operation of the device; in fact, at 85C, the AAT4280A will handle a 2A pulse for up to 50% duty cycle. At lower ambient temperatures, the duty cycle can be further increased.
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. For example, a 4V system using an AAT4280A operates at a continuous 100mA load current level and has short 2A current peaks, as in a GSM application. The current peak occurs for 576s out of a 4.61ms period. First, the current duty cycle is calculated: % Peak Duty Cycle: X/100 = 576s/4.61ms % Peak Duty Cycle = 12.5% The load current is 100mA for 87.5% of the 4.61ms period and 2A for 12.5% of the period. Since the Electrical Characteristics do not report RDS(MAX) for 4V operation, it must be calculated approximately by consulting the chart of RDS(ON) vs. VIN. The RDS
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AAT4280A
Slew Rate Controlled Load Switch Printed Circuit Board Layout Recommendations
For proper thermal management and to take advantage of the low RDS(ON) of the AAT4280A, a few circuit board layout rules should be followed: VIN and VOUT should be routed using wider than normal traces, and GND should be connected to a ground plane. To maximize package thermal dispation and power handling capacity of the AAT4280A SC70JW-8 package, the ground plane area connected 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 AAT4280A evaluation layout follows the printed circuit board layout recommendations and can be used for good applications layout. Refer to Figures 1 through 3. Note: Board layout shown is not to scale.
Figure 1: Evaluation Board Top Side Silk Screen Layout / Assembly Drawing.
Figure 2: Evaluation Board Component Side Layout.
Figure 3: Evaluation Board Solder Side Layout.
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AAT4280A
Slew Rate Controlled Load Switch Ordering Information
Device Option
AAT4280A-1 AAT4280A-2 AAT4280A-3
Package
SC70JW-8 SC70JW-8 SC70JW-8
Marking1
NDXYY NEXYY NFXYY
Part Number (Tape and Reel)2
AAT4280AIJS-1-T1 AAT4280AIJS-2-T1 AAT4280AIJS-3-T1
Notes: 1. XYY = assembly and date code. 2. Sample stock is generally held for part numbers listed in BOLD.
Package Information
SC70JW-8
0.50 BSC 0.50 BSC 0.50 BSC
1.75 0.10 0.225 0.075 2.00 0.20
2.20 0.20
0.048REF 0.15 0.05
0.85 0.15
1.10 MAX
0.100
7 3
0.45 0.10 2.10 0.30
4 4
All dimensions in millimeters.
0.05 0.05
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AAT4280A
Slew Rate Controlled Load Switch
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 14
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