SmartSwitch™
General Description
The AAT4250 SmartSwitch™ is a member of
AATI's Application Specific Power MOSFET™
(ASPM™) product family. It is a Slew Rate
Controlled P-channel MOSFET power switch
designed for high-side load-switching applications.
This switch operates with an input voltage range
from 1.8V to 5.5V, making it ideal for 2.5V, 3.3V or
5V systems. The part features 1.5ms turn on and
10µs turn off time. The AAT4250 has an under volt-
age lock out which turns off the switch when an
under-voltage condition exists. Input logic levels
are TTL compatible. The quiescent supply current
is very low, typically 2µA. In shutdown mode, the
supply current is typically reduced to 0.1µA or less.
The AAT4250 is available in a 5-pin SOT23 (SOT25)
and 8-pin SC70JW specified over -40 to 85°C.
Features
• 1.8V to 5.5V Input voltage range
• 120mΩ(5V) typical RDS(ON)
• Low quiescent current
• Typical 2µA
• Typical 0.1µA with Enable off
• Only 2.0V needed for ON/OFF Control
• Temperature range -40º to 85°C
• 5kV ESD rating
• 5-pin SOT23 (SOT25) or SC70JW-8 package
Applications
• Hot swap supplies
• Notebook computers
• Personal communication devices
AAT4250
Slew Rate Controlled Load Switch
Typical Application
AAT4250
ON/OFF
IN OUT
GND
ON
1µF0.1µF
INPUT
GND GND
CIN COUT
OUTPUT
Preliminary Information
4250.2002.5.0.95 1
Pin Descriptions
Pin Configuration
SOT23-5 (SOT25)
(Top View)
SC70JW-8
(Top View)
GND
GND
GND
1 2
IN
IN
ON/OFF
GND
OUT
1
2
3
4
8
7
6
5
1
2
3
NC
OUT
4
5
GND
IN
ON/OFF
Pin #
SOT23-5 SC70JW Symbol Function
1 1 OUT P-channel MOSFET drain
2 2, 3, 4, 5 GND Ground connection
3 n/a NC Not internally connected
4 6 ON/OFF Active-High Enable Input (Logic high turns the switch on)
5 7, 8 IN P-channel MOSFET source
AAT4250
Slew Rate Controlled Load Switch
24250.2002.5.0.95
Absolute Maximum Ratings (TA=25°C 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 1.5kΩresistor into each pin.
Thermal Characteristics
Note 2: Mounted on an AAT4250 demo board in still 25ºC air.
Electrical Characteristics (VIN = 5V, TA= -40 to 85°C unless otherwise noted. Typical values
are at TA=25°C)
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.
Symbol Description Conditions Min Typ Max Units
VIN Operation Voltage 1.8 35.5 V
IQQuiescent Current VIN = 5V, ON/OFF = VIN, IOUT = 0 2 4 µA
IQ(OFF) Off Supply Current ON/OFF = GND, VIN = 5V, OUT open 1 µA
ISD(OFF) Off Switch Current ON/OFF = GND, VIN = 5V, VOUT = 0 0.1 1 µA
VUVLO Undervoltage Lockout VIN falling 1.0 1.5 1.8 V
VUVLO(hys) Undervoltage Lockout hysteresis 250 mV
VIN = 5V, TA= 25º C 120 175 mΩ
RDS(ON) On-Resistance VIN = 3V, TA= 25º C 135 200 mΩ
VIN =1.8V 165 mΩ
TCRDS On-Resistance Temp-Co 2800 ppm/ºC
VIL ON/OFF Input Logic Low Voltage VIN = 2.7V to 5.5V 40.8 V
VIH ON/OFF Input Logic High Voltage VIN = 2.7V to ≤ 4.2V 2.0 V
VIN = > 4.2V to 5.5V 2.4
ISINK ON Input leakage VON = 5V 0.01 1 µA
TDOutput Turn-On Delay Time 300 µs
TDOFF Turn-Off Delay Time VIN=5V, RLOAD=10Ω10 µs
VIN=3V, RLOAD=5Ω10
VIN=5V, RLOAD=16.5Ω, TA=0 to 50º C 1000
TON Turn-On Rise Time VIN=5V, RLOAD=10Ω, COUT=0.1µF 1500 µs
VIN=3V, RLOAD=5Ω, COUT=0.1µF 1500
Symbol Description Value Units
ΘJA Thermal Resistance (SOT23-5 [SOT25] or SC70JW-8)2150 °C/W
PDPower Dissipation (SOT23-5 [SOT25]or SC70JW-8)2667 mW
Symbol Description Value Units
VIN IN to GND -0.3 to 6 V
VON ON/OFF to GND -0.3 to 6 V
VOUT OUT to GND -0.3 to VIN+0.3 V
IMAX Maximum Continuous Switch Current 1.7 A
IDM Maximum Pulsed Current IN ≥2.5V 4 A
IN < 2.5V 2 A
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at Leads) 300 °C
VESD ESD Rating1- HBM 5000 V
AAT4250
Slew Rate Controlled Load Switch
4250.2002.5.0.95 3
Typical Characteristics
(Unless otherwise noted, VIN = 5V, TA= 25°C)
Turn-On Time vs. Temperature
0.5
1.0
1.5
2.0
2.5
3.0
-40 -20 0 20 40 60 80 100
Temperature (°C)
Turn-ON Time (ms)
CIN=1µF, COUT=0.1µF
VIN=5V
RLOAD=10Ω
VIN=3V
RLOAD=5Ω
Turn-OFF Time vs. Temperature
5
6
7
8
9
10
-40 -20 0 20 40 60 80 100
Temperature (°C)
CIN=1µF, COUT=0.1µF
Turn-OFF Time (µs)
VIN=5V
RLOAD=10Ω
VIN=3V
RLOAD=5Ω
Off-Switch Current vs. Temperature
1
10
100
1000
10000
-40 -20 0 20 40 60 80 100
Temperature (°C)
Off-Switch Current (nA)
Off-Supply Current vs. Temperature
1
10
100
1000
-40 -20 0 20 40 60 80 100
Temperature (°C)
Off-Supply Current (nA)
Quiescent Current vs. VIN
0
0.5
1
1.5
2
2.5
3
3.5
4
0 12 3456
Quiescent Current (µA)
VIN
Quiescent Current vs. Temperature
0
0.5
1
1.5
2
2.5
3
3.5
4
-40 -20 0 20 40 60 80 100
Temperature (°C)
Quiescent Current (µA)
VIN=3V
VIN=5V
AAT4250
Slew Rate Controlled Load Switch
44250.2002.5.0.95
(Unless otherwise noted, VIN = 5V, TA= 25°C)
1
3
5
CIN=1µ
F,COUT =1µ
F,VIN=5V
Turn Off Waveforms
Time (
µs)
-1
-1 1 3 5 7 9 11 13 15
V(out)
Volt
V(ON/OFF)
0
1
2
3
4
CIN=1µF,COUT =1µF,VIN=3V
Turn Off Waveforms
Time (µs)
-1
-1 1 3 5 7 9 11 13 15
V(out)
Volt
V(ON/OFF)
-1 0 1 2 3 4
0
1
1.2
Time (ms)
CIN=1µ
F,COUT =10
µF,VIN=5V
Turn On Waveforms
V(out) 0.8
0.6
0.4
0.2
5
6
I(in)
Volt
4
3
2
1
0
A
V(ON/OFF)
Volt
-1 0 1 2 3 4
0
1
2
3
4
0
0.5
1
1.5
2
Time (ms)
CIN=1µF,COUT =10µF,VIN=3V
Turn On Waveforms
V(out)
I(in)
A
V(ON/OFF)
Volt
-1 0 1 2 3 4
0
1
2
3
4
0
1
1.2
Time (ms)
CIN=1µF,COUT =0.1µF,VIN=5V
Turn On Waveforms
V(out) 0.8
0.6
0.4
0.2
5
6
I(in)
A
V(ON/OFF)
Volt
-1 0 1 2 3 4
0
1
2
3
4
0
0.5
1
1.5
2
Time (ms)
CIN=1µF,COUT=0.1
µF,VIN=3V
Turn On Waveforms
V(ON/OFF)
V(out)
I(in)
A
AAT4250
Slew Rate Controlled Load Switch
4250.2002.5.0.95 5
(Unless otherwise noted, VIN = 5V, TA= 25°C)
Typical ON/OFF Threshold vs. VIN
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VIN
ON/OFF Threshold
VIH
VIL
RDS(ON) vs. VIN
110
120
130
140
150
160
170
180
190
1.5 2 2.5 3 3.5 4 4.5 5 5.5
VIN
RDS(ON) (mΩ)
IOUT = 100mA
RDS(ON) vs. Temperature
80
90
120
110
100
150
140
130
160
-40 -20 0 20 40 60 80 100
Temperature (°C)
RDS(ON) (mΩ)
VIN=3V
VIN=5V
AAT4250
Slew Rate Controlled Load Switch
64250.2002.5.0.95
Functional Description
The AAT4250 is a slew rate controlled P-channel
MOSFET power switch designed for high-side load-
switching applications. It operates with input volt-
ages ranging from 1.8V 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 1.8V, the AAT4250 MOS-
FET is protected from entering the saturated region
of operation by automatically shutting down. In
addition, the TTL compatible ON/OFF pin makes
the AAT4250 an ideal level shifted load-switch. The
slew rate controlling feature eliminates in-rush cur-
rent when the MOSFET is turned on, allowing the
AAT4250 to be implemented with a small input
capacitor, or no input capacitor at all. During slew-
ing, 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 quick-
ly 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.
AAT4250
Slew Rate Controlled Load Switch
4250.2002.5.0.95 7
Functional Block Diagram
Under-
voltage
Lockout
Level
Shift
Slew Rate
Control
IN
ON/OFF
GND
OUT
Applications Information
Input Capacitor
Typically a 1µF or larger capacitor is recommend-
ed for CIN in most applications. A CIN capacitor is
not required for basic operation, however, it is use-
ful in preventing load transients from affecting up
stream 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 cur-
rent operation, ceramic capacitors are recom-
mended for CIN due to their inherent capability over
tantalum capacitors to withstand input current
surges from low impedance sources such as bat-
teries in portable devices.
Output Capacitor
For proper slew operation, a 0.1µF capacitor or
greater between VOUT and GND is required.
Likewise, with the output capacitor, there is no spe-
cific capacitor ESR requirement. If desired, COUT
maybe increased without limit to accommodate any
load transient condition without adversely affecting
the slew rate.
Enable Function
The AAT4250 features an enable / disable function.
This pin (ON) is active high and is compatible with
TTL or CMOS logic. To assure the load switch will
turn on, the ON control level must be greater than
2.0 volts. The load switch will go into shutdown
mode when the voltage on the ON pin falls below
0.8 volts. When the load switch is in shutdown
mode, the OUT pin is tristated, and quiescent cur-
rent drops to leakage levels below 1µA.
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 main-
taining 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 possibly damage
the load switch.
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 capaci-
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 schot-
tky diode from VIN to VOUT (connecting the cathode
to VIN and anode to VOUT). The Schottky diode for-
ward voltage should be less then 0.45 volts.
Thermal Considerations and High
Output Current Applications
The AAT4250 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 utiliz-
ing the minimum recommended footprint as stated
in the layout considerations section.
At any given ambient temperature (TA) the maxi-
mum package power dissipation can be deter-
mined by the following equation:
PD(MAX) = [TJ(MAX) - TA] / ΘJA
Constants for the AAT4250 are maximum junction
temperature, TJ(MAX) = 125°C, and package thermal
resistance, ΘJA = 150°C/W. Worst case conditions
are calculated at the maximum operating tempera-
ture where TA= 85°C. Typical conditions are cal-
culated under normal ambient conditions where TA
= 25°C. At TA= 85°C, PD(MAX) = 267mW. At TA=
25°C, PD(MAX) = 667mW.
The maximum continuous output current for the
AAT4250 is a function of the package power dissi-
pation and the RDS of the MOSFET at TJ(MAX). The
maximum RDS of the MOSFET at TJ(MAX) is calcu-
lated by increasing the maximum room tempera-
ture RDS by the RDS temperature coefficient. The
temperature coefficient (TC) is 2800ppm/°C.
Therefore, at 125°C
RDS(MAX) = RDS(25°C) × (1 + TC × ∆T)
RDS(MAX) = 175mΩ × (1 + .002800 × (125°C-25°C))
RDS(MAX) = 224mΩ
AAT4250
Slew Rate Controlled Load Switch
84250.2002.5.0.95
For maximum current, refer to the following equation:
IOUT(MAX) < ( PD(MAX) / RDS)1/2
For example, if VIN = 5V, RDS(MAX)=224mΩand TA
= 25°C, IOUT(MAX) = 1.7A. If the output load current
were to exceed 1.7A 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
AAT4250. 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. Duty cycles with peaks less than
2ms in duration can be considered using the
method below.
High Peak Output Current Applications
Some applications require the load switch to oper-
ate at a continuous nominal current level with short
duration high current peaks. Refer to the IDM spec-
ification in the Absolute Maximum table to ensure
the AAT 4250’s maximum pulsed current rating is
not exceeded. The duty cycle for both output cur-
rent 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 addi-
tional power dissipation due to the short duration
high current peak scaled by the duty factor.
For example, a 4V system using an AAT4250 oper-
ates at a continuous 100mA load current level and
has short 2A current peaks, as in a GSM applica-
tion. The current peak occurs for 576µs out of a
4.61ms period.
First, the current duty cycle is calculated:
% Peak Duty Cycle: X/100 = 576µs/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
volts operation, it must be calculated approximated
by consulting the chart of RDSON vs. VIN. The Rds
reported for 5 volt RDS can be scaled by the ratio
seen in the chart to derive the Rds for 4 volt VIN:
175mΩx 120mΩ/115mΩ= 183mΩ. Derated for
temperature: 183mΩx (1 + .002800 x (125°C -
25°C)) = 235mΩ. The power dissipation for a
100mA load is calculated as follows:
PD(MAX) = I2OUT x RDS
PD(100mA) = (100mA)2x 235mΩ
PD(100mA) = 2.35mW
PD(87.5%D/C) = %DC x PD(100mA)
PD(87.5%D/C) = 0.875 x 2.35mW
PD(87.5%D/C) = 2.1mW
The power dissipation for 100mA load at 87.5%
duty cycle is 2.1mW. Now the power dissipation for
the remaining 12.5% of the duty cycle at 2A is cal-
culated:
PD(MAX) = I2OUT x RDS
PD(2A) = (2A)2x 235mΩ
PD(2A) = 940mW
PD(12.5%D/C) = %DC x PD(2A)
PD(12.5%D/C) = 0.125 x 940mW
PD(12.5%D/C) = 117.5mW
The power dissipation for 2A load at 12.5% duty
cycle is 117mW. Finally, the two power figures are
summed to determine the total true power dissipa-
tion under the varied load.
PD(total) = PD(100mA) + PD(2A)
PD(total) = 2.1mW + 117.5mW
PD(total) = 120mW
The maximum power dissipation for the AAT4250
operating at an ambient temperature of 85°C is
267mW. The device in this example will have a
total power dissipation of 120mW. This is well with
in the thermal limits for safe operation of the
device, in fact, at 85°C, the AAT4250 will handle a
2A pulse for up to 28% duty cycle. At lower ambi-
ent temperatures the duty cycle can be further
increased.
AAT4250
Slew Rate Controlled Load Switch
4250.2002.5.0.95 9
AAT4250
Slew Rate Controlled Load Switch
10 4250.2002.5.0.95
Figure 1: Evaluation board Figure 2: Evaluation board Figure 3: Evaluation board
top side silk screen layout / component side layout solder side layout
assembly drawing
Printed Circuit Board Layout
Recommendations
For proper thermal management, and to take
advantage of the low RDSON of the AAT4250, 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. For best performance, CIN and COUT should
be placed close to the package pins.
Evaluation Board Layout
The AAT4250 evaluation layout follows the printed
circuit board layout recommendations, and can be
used for good applications layout.
Note: Board layout shown is not to scale.
AAT4250
Slew Rate Controlled Load Switch
4250.2002.5.0.95 11
Ordering Information
Note: Sample stock is generally held on all part numbers listed in BOLD.
Note 1: XYY = assembly and date code.
Package Information
SOT23-5 (SOT25)
All dimensions in millimeters.
4° ± 4°
0.15 ± 0.07
0.45 ± 0.15 0.10 BSC
1.20
±
0.25
1.575 ± 0.125
2.80 ± 0.20
0.40
±
0.10
0.60 REF
2.85 ± 0.15
1.90 BSC
0.95
BSC
1.10
±
0.20
10°
±
5°
GAUGE PLANE
0.075
±
0.075
0.60 REF
Package Marking1Part Number (Tape and Reel)
SOT23-5 (SOT25) ACXYY AAT4250IGV-T1
SC70JW-8 ACXYY AAT4250IJS-T1
SC70JW-8
All dimensions in millimeters.
0.225 ± 0.075
0.45 ± 0.10
0.05 ± 0.05
2.10 ± 0.30
2.00 ± 0.20
7° ± 3°4° ± 4°
1.75 ± 0.10
0.85 ± 0.15
0.15 ± 0.05
1.10 MAX
0.100
2.20 ± 0.20
0.048REF
0.50 BSC 0.50 BSC 0.50 BSC
AAT4250
Slew Rate Controlled Load Switch
12 4250.2002.5.0.95
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
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