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Slew Rate Controlled Load Switch General Description
The AAT4280 SmartSwitchTM is a member of AATI's Application Specific Power MOSFETTM (ASPMTM) product family. The AAT4280 is a P-channel MOSFET power switch designed for high-side loadswitching applications. The P-channel MOSFET device has a typical RDS(ON) of 80m, allowing increased load switch power handling capacity. This device is available in three different versions with flexible turn on and off characteristics from very fast to slew rate limited. The standard AAT4280 (-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 AAT4280 (-2) version features fast load switch turn on capabilities, typically less than 500ns turn on and 3s turn off times. The AAT4280 (-3) variation offers a shutdown load discharge circuit to rapidly turn off a load circuit when the switch is disabled. All AAT4280 load switch versions operate with an input voltage ranging from 1.8V to 5.5V, making them ideal for both 3V and 5V systems. The AAT4280 also features an under voltage lock out which turns the switch off when an input under-voltage condition exists. Input logic levels are TTL and 2.5 volt to 5 volt CMOS compatible. The quiescent supply current is very low, typically 2.5A. In shutdown mode, the supply current decreases to less than 1A. The AAT4280 is available in a 6 pin SOT23 or 8 pin SC70JW package and is specified over -40C to 85C temperature range.
AAT4280
Features
* * *
SmartSwitchTM
* * * * * *
1.8V 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 * 2.5A typ * 1A max in shutdown TTL/CMOS input logic level Temperature range -40C to 85C 4kV ESD rating 6 pin SOT23 or SC70JW-8 package
Applications
* * * * * * Cellular telephones Digital still cameras Personal digital assistants (PDA) Hot swap supplies Notebook computers Personal communication devices
Typical Application
V IN
IN IN C IN 1F ON ON/OFF GND GND
OUT
V OUT
AAT4280
C OUT 0.1F
GND
GND
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Slew Rate Controlled Load Switch Pin Descriptions
Pin # SOT23-6
1 2,5 3 4,6
AAT4280
SC70JW
2 4 3 1,5,6,7,8
Symbol
OUT GND ON/OFF IN
Function
The pin is the P-channel MOSFET drain connection. Bypass to ground through a 0.1uF capacitor. Ground connection Enable Input The pin is the input to the P-channel MOSFET source. Bypass to ground through a 1.0uF capacitor.
Pin Configuration
SOT23-6 (Top View)
OUT GND ON/OFF
1
6
IN GND IN
2
5
3
4
SC70JW-8 (Top View)
IN OUT ON/OFF GND
1 2 3 4
8 7 6 5
IN IN IN IN
Selector Guide
Part Number
AAT4280-1 AAT4280-2 AAT4280-3
Slew Rate (typ)
1mS 0.5S 100S
Active Pull Down
Enable
Active High Active High
Active High
2
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Slew Rate Controlled Load Switch Absolute Maximum Ratings
Symbol
VIN VON VOUT IMAX IDM TJ TLEAD VESD
AAT4280
(TA=25C unless otherwise noted) Value
-0.3 to 6 -0.3 to 6 -0.3 to VIN+0.3 2.3 6 3 -40 to 150 300 4000
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 Rating1 - HBM IN 2.5V IN < 2.5V
Units
V V V A A 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
Value Symbol
JA PD
Description
Thermal Resistance (SOT23-6 or SC70JW-8) Power Dissipation (SOT23-6 or SC70JW-8)2
2
SOT23-6
SC70JW-8
Units
C/W mW
120 833
140 714
Note 2: Mounted on an AAT4280 demo board in still 25C air.
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Slew Rate Controlled Load Switch Electrical Characteristics
are at TA=25C) Symbol Description Conditions Min
1.8 3 1.0
AAT4280
(VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values Typ Max
5.5 1.8 4 1 1 120 130 150 250 0.8 2 2.4 1 20 1000 4 0.5 0.5 4 20 100 4 150 40 1500 10 2 1 10 40 150 10 250
Units
V V mV uA uA uA m
AAT4280 All Versions VIN Operation Voltage VUVLO Undervoltage Lockout VUVLO(hys) Undervoltage Lockout Hysteresis IQ Quiescent Current IQ(off) Off supply current ISD(off) Off switch current RDS(on) On -resistance
VIN falling ON/OFF= active ON/OFF= inactive, OUT=open ON/OFF= inactive, VOUT=0 VIN=5V, TA=25 C VIN=4.2V, TA=25 C VIN=3V, TA=25 C VIN=1.8V, TA=25 C VIN=2.7V-5.5V 4 VIN=2.7V to 4.2V VIN= >4.2V to 5.5V VON/OFF= 5.5V VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C VIN =5V, RLOAD=10, TA=25 C ON/OFF = inactive, TA=25 C
1.4 250 2.5
TCRDS VIL VIH
On-Resistance Temp -Co ON/OFF Input Logic Low Voltage ON/OFF Input Logic High Voltage
80 85 100 160 2800
ISINK ON/OFF Input Leakage AAT4280-1 TD(ON) Output Turn-On Delay TON Output Turn-On rise time TD(OFF) Output Turn-Off delay time AAT4280-2 TD(ON) Output Turn-On Delay TON Output Turn-On rise time TD(OFF) Output Turn-Off delay time AAT4280-3 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
ppm/C V V V uA uS uS uS uS uS uS uS uS uS
Note 3: Part requires minimum start-up of VIN 2.0V to ensure operation down to 1.8V Note 4: For VIN outside this range consult typical ON/OFF threshold curve.
4
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Slew Rate Controlled Load Switch Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA = 25C) Quiescent Current vs. Temperature
4 3.5
AAT4280
Quiescent Current vs. Input Voltage
Quiescent Current (A)
80 100
3
VIN=5V
3.0 2.5 2.0 1.5 1.0 0.5 0.0
IQ (A)
2
1
VIN=3V
0 -40 -20 0 20 40 60
0
1
2
3
4
5
6
Temperature (C)
VIN (V)
RDS(ON) vs. VIN
190 170 120
RDS(ON) vs. Temperature
2A RDS(ON) (m) 1A 500mA 100mA
110 100 90 80 70 60 50
RDS(ON) (m)
VIN=3V
150 130 110 90 70 1.5 2.0
VIN=5V
2.5
3.0
3.5
4.0
4.5
5.0
5.5
40 -40 -20 0 20 40 60 80 100
VIN (V)
Temperature (C)
ON/OFF Threshold vs. VIN
ON/OFF Threshold (V)
2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0.001 -40 1.000
Off Switch Current vs. Temperature
VIL
IOFFSW (A)
VIH
0.100
0.010
VIN (V)
-20
0
20
40
60
80
100
Temperature (C)
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Slew Rate Controlled Load Switch Typical Characteristics--4280-1
(Unless otherwise noted, VIN = 5V, TA = 25C) AAT4280-1 Turn-On VIN=3V RL=6
ON/OFF (5V/div.) VOUT (2V/div.)
AAT4280
AAT4280-1 Turn-On VIN=5V RL=10
ON/OFF (5V/div.)
VOUT (2V/div.)
IIN (200mA/div.)
IIN (200mA/div.) Time (500s/div.)
Time (500s/div.)
AAT4280-1 Turn-Off VIN=3V RL=6
ON/OFF (5V/div.)
AAT4280-1 Turn-Off VIN=5V RL=10
ON/OFF (5V/div.)
VOUT (2V/div.)
VOUT (2V/div.)
IIN (200mA/div.) Time (10s/div)
IIN (200mA/div.) Time (10s/div.)
6
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Slew Rate Controlled Load Switch Typical Characteristics--4280-2
(Unless otherwise noted, VIN = 5V, TA = 25C) AAT4280-2 Turn-On VIN=3V RL=6
ON/OFF (5V/div.) VOUT (2V/div.)
AAT4280
AAT4280-2 Turn-On VIN=5V RL=10
ON/OFF (5V/div.)
VOUT (2V/div.)
IIN (200mA/div.) Time (5s/div.) Time (5s/div.)
IIN (200mA/div.)
AAT4280-2 Turn-Off VIN=3V RL=6
AAT4280-2 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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Slew Rate Controlled Load Switch Typical Characteristics--4280-3
(Unless otherwise noted, VIN = 5V, TA = 25C) AAT4280-3 Turn-On VIN=3V RL=6
ON/OFF (5V/div.) VOUT (2V/div.)
AAT4280
AAT4280-3 Turn-On VIN=5V RL=10
ON/OFF (5V/div.)
VOUT (2V/div.)
IIN (200mA/div.)
IIN (200mA/div.) Time (50s/div.)
Time (50s/div.)
AAT4280-3 Turn-Off VIN=3V RL=6
AAT4280-3 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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Slew Rate Controlled Load Switch Functional Block Diagram
IN
Under Voltage Lockout Level Shift Turn-On Slew Rate Control
AAT4280
OUT
*
ON/OFF
GND
*AAT4280-3 only
Functional Description
The AAT4280 is a family of flexible P-channel MOSFET power switches designed for high-side load-switching applications. There are three versions of AAT4280 with different turn-on and turn-off characteristics to choose from, depending upon the specific requirements of an application. The first AAT4280-1 version 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 device version, the AAT4280-2 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 AAT4280-3 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 AAT4280 operate with input voltages ranging from 1.8V to 5.5V. All versions of this device have extremely low operating current, making them ideal for battery-powered applications. In cases where the input voltage drops below 1.8V, the AAT4280 MOSFET device is protected from entering into the saturation region of operation by automatically shutting down through an under voltage lockout control circuit. The ON/OFF control pin is TTL compatible and will also function with 2.5 volt to 5 volt logic systems, making the AAT4280 an ideal level shifting load-switch. 9
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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. tor 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 then 0.45 volts.
AAT4280
Thermal Considerations and High Output Current Applications
The AAT4280 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 AAT4280 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 AAT4280 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 AAT4280 features an enable / disable function. This pin (ON/OFF) is compatible with both TTL or CMOS logic.
Reverse Output to Input Conditions and Protection
Voltage
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 operation, the use of a larger value CIN capaci-
10
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Slew Rate Controlled Load Switch
For maximum current, refer to the following equation: IOUT(MAX) < ( PD(MAX) / RDS)
1/2
AAT4280
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 will increase, and the device will be damaged. Higher peak currents can be obtained with the AAT4280. 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.
ratio seen in the chart to derive the RDS for a 4 volt 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 AAT4280 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 with in the thermal limits for safe operation of the device, in fact, at 85C, the AAT4280 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 AAT4280 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 4 volt operation, it must be calculated approximately by consulting the chart of RDS(ON) vs. VIN. The RDS reported for 5 volts can be scaled by the
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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 AAT4280, 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 AAT4280 SOT23-6/ 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.
AAT4280
Evaluation Board Layout
The AAT4280 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
12
4280.2004.07.1.1
Slew Rate Controlled Load Switch Ordering Information
Device Option AAT4280-1 AAT4280-2 AAT4280-3 AAT4280-1 AAT4280-2 AAT4280-3 Package SOT23-6 SOT23-6 SOT23-6 SC70JW-8 SC70JW-8 SC70JW-8 Marking1 COXYY BZXYY CJXYY COXYY BZXYY CJXYY Part Number (Tape and Reel) AAT4280IGU-1-T1 AAT4280IGU-2-T1 AAT4280IGU-3-T1 AAT4280IJS-1-T1 AAT4280IJS-2-T1 AAT4280IJS-3-T1
AAT4280
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
Package Information
SOT23-6
2.85 0.15 1.90 BSC 0.95 BSC
1.575 0.125
1.10 0.20
2.80 0.20 1.20 0.25
0.075 0.075
0.15 0.07 4 4
GAUGE PLANE
10 5 0.40 0.10 x 6
0.60 REF
0.45 0.15
0.10 BSC
All dimensions in millimeters.
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Slew Rate Controlled Load Switch
SC70JW-8
0.50 BSC 0.50 BSC 0.50 BSC
AAT4280
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.
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4280.2004.07.1.1
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