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PDF AAT4280 Data sheet ( Hoja de datos )
| Número de pieza | AAT4280 | |
| Descripción | Slew Rate Controlled Load Switch | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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General Description
The AAT4280 SmartSwitch is a P-channel MOSFET
power switch designed for high-side load switching
applications. The P-channel MOSFET device has a
typical RDS(ON) of 80mΩ, allowing increased load
switch power handling capacity. This device is avail-
able in three different versions with flexible turn on
and off characteristics from very fast to slew rate lim-
ited. 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 3µs 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-volt-
age lockout which turns the switch off when an input
under-voltage condition exists. Input logic levels are
TTL and 2.5V to 5V CMOS compatible. The quies-
cent supply current is very low, typically 2.5µA. In
shutdown mode, the supply current decreases to
less than 1µA.
The AAT4280 is available in a Pb-free, 6-pin
SOT23 or 8-pin SC70JW package and is specified
over the -40°C to +85°C temperature range.
AAT4280
Slew Rate Controlled Load Switch
Features
SmartSwitch™
• 1.8V to 5.5V Input Voltage Range
• Very Low RDS(ON), Typically 80mΩ (5V)
• Slew Rate Limited Turn-On Time Options
— 1ms
— 0.5µs
— 100µs
• Fast Shutdown Load Discharge Option
• Low Quiescent Current
— 2.5µA Typical
— 1µA Max in Shutdown
• TTL/CMOS Input Logic Level
• Temperature Range: -40ºC to +85°C
• 4kV ESD Rating
• 6-Pin SOT23 or 8-Pin SC70JW Package
Applications
• Cellular Telephones
• Digital Still Cameras
• Hot Swap Supplies
• Notebook Computers
• Personal Communication Devices
• Personal Digital Assistants (PDA)
Typical Application
VIN
C IN
1μF
IN OUT
IN AAT4280
ON ON/OFF
GND GND
GND
4280.2006.11.1.4
V OUT
C OUT
0.1μF
GND
1
1 page  
AAT4280
Slew Rate Controlled Load Switch
Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25°C.
Quiescent Current vs. Temperature
4
VIN = 5V
3
2
1 VIN = 3V
0
-40
-20
0
20 40 60 80 100
Temperature (°C)
Quiescent Current vs. Input Voltage
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
12 3 4 5
Input Voltage (V)
6
RDS(ON) vs. Input Voltage
190
2A
170
150 1A
500mA
130
110
100mA
90
70
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Input Voltage (V)
RDS(ON) vs. Temperature
120
110
100
90
80
70
60
50
40
-40
-20
VIN = 3V
VIN = 5V
0 20 40 60
Temperature (°C)
80 100
ON/OFF Threshold vs. Input Voltage
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
1.5
2.0
VIH
VIL
2.5 3.0
3.5 4.0
4.5 5.0 5.5
Input Voltage (V)
4280.2006.11.1.4
Off-Switch Current vs. Temperature
1.000
0.100
0.010
0.001
-40
-20
0 20 40 60
Temperature (°C)
80 100
5
5 Page 
AAT4280
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) = 154mΩ and TA
= 25°C, 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
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.
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. The duty cycle for
both output current levels must be taken into
account. To do so, first calculate the power dissi-
pation 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 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
4V operation, it must be calculated approximately
by consulting the chart of RDS(ON) vs. VIN. The RDS
reported for 5V can be scaled by the ratio seen in
the chart to derive the RDS for a 4V VIN: 120mΩ ·
87mΩ /80mΩ = 130mΩ. De-rated for temperature:
130mΩ x (1 + 0.0028 · (125°C -25°C)) = 166mΩ.
The power dissipation for a 100mA load is calculat-
ed as follows:
PD(MAX) = IOUT2 · RDS
PD(100mA) = (100mA)2 · 166mΩ
PD(100mA) = 1.66mW
PD(87.5%D/C) = %DC · PD(100mA)
PD(87.5%D/C) = 0.875 · 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 · RDS
PD(2A) = (2A)2 · 166mΩ
PD(2A) = 664mW
PD(12.5%D/C) = %DC · PD(2A)
PD(12.5%D/C) = 0.125 · 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 dissipa-
tion 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 85°C 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 85°C, the AAT4280 will handle a
2A pulse for up to 50% duty cycle. At lower ambi-
ent temperatures, the duty cycle can be further
increased.
4280.2006.11.1.4
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet AAT4280.PDF ] | |
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