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DATA SHEET
AAT4616A: High Precision Adjustable Current Limited
Load Switch with Fault Flag
Applications
USB ports
Portable products
Hot-swap supplies
Notebook computers
Proprietary peripheral ports
Features
Input voltage: 2.4 V to 5.5 V
Programmable over-current limit setting: 300 mA to 1.6 A
±10% current limit precision at 750 mA
Fast transient response: 2 µs response to short circuit
Low quiescent current
10 µA typical while enabled
1 µA maximum with switch off
130 m typical RDS(ON)
Under-Voltage Lockout (UVLO)
Reverse blocking during disable
4 ms fault blanking
Fault flag open-drain output
Active high/low enable options
Over-temperature protection
Temperature range: 40 °C to +85 °C
TDFN (6-pin, 2 x 2 mm) package (MSL1, 260 °C per
JEDEC-J-STD-020)
Description
The AAT4616A SmartSwitch is a current-limiting P-channel
MOSFET power switch designed for high side load switching
applications. This switch operates with inputs ranging from 2.4 V
to 5.5 V, making it ideal for both 3 V and 5 V systems. An
integrated current-limiting circuit protects the input supply
against large currents that may cause the supply to fall out of
regulation. Reverse current blocking is provided to protect the
load switch from reverse current potentials while the device is
shutdown.
The AAT4616A is also protected from thermal overload which is
limited by power dissipation and junction temperatures. The
current limit threshold is programmed with a resistor from SET to
ground and may be adjusted for levels up to 1.6 A. The ultra-fast
current limit response to a sudden short circuit is a mere 2 µs,
which reduces the requirements of local supply bypassing. An
open drain FAULT flag signals an over-current or over-
temperature condition after a 4 ms blanking time to prevent false
reporting. Quiescent current is as low as 10 µA and the supply
current decreases to less than 1 µA in shutdown mode.
The AAT4616A is offered in a small Thin, Dual Flat No-Lead
(TDFN22-6) package. A typical application circuit is shown in
Figure 1. The pin configuration is shown in Figure 2. Signal pin
assignments and functional pin descriptions are provided in
Table 1.
Figure 1. AAT4616A Typical Application Circuit
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Figure 2. AAT4616A TDFN22-6
(Top View)
Table 1. AAT4616A Signal Descriptions
Pin # Name Description
1 OUT Current limiting load switch output (high side P-channel MOSFET drain). Connect a 0.47 µF capacitor from OUT to GND for best
load transient response.
2 SET Current limit set pin. Connect a resistor between this pin and ground to program the desired current limit set point.
3 FLT Current limit fault flag pin, open-drain output, active low signal. Pull up with a 10 k to 100 k resistor.
4 ON/ON Load switch enable input. Active high and active low options are available.
5 GND Ground
6 IN Load switch power supply input pin (high side P-channel MOSFET source). Bypass with a 1 µF capacitor from IN to GND.
Table 2. AAT4616A Absolute Maximum Ratings (Note 1)
Parameter Symbol Minimum Typical Maximum Units
IN to GND VIN 0.3 +6.0 V
ON/ON,FLT to GND VON, VFLT 0.3 VIN + 0.3 V
SET, OUT to GND VSET, VOUT 0.3 VIN + 0.3 V
Maximum DC output current (Note 2) IMAX 2 A
Operating junction temperature range TJ 40 +150 ºC
Storage temperature range TSTG 40 +150 ºC
Maximum Soldering Temperature (at leads) TLEAD 300 ºC
Thermal resistance θJA 85 ºC/W
Power dissipation (Note 3) PD 1.18 W
Note 1: Exposure to maximum rating conditions for extended periods may reduce device reliability. There is no damage to device with only one parameter set at the limit and all other
parameters set at or below their nominal value. Exceeding any of the limits listed may result in permanent damage to the device.
Note 2: The current rating is based on long-term current density limitations.
Note 3: Mounted on an FR4 board. Derated 11.8 mW/ ºC above 25 ºC.
CAUTION: Although this device is designed to be as robust as possible, Electrostatic Discharge (ESD) can damage this device. This device
must be protected at all times from ESD. Static charges may easily produce potentials of several kilovolts on the human body
or equipment, which can discharge without detection. Industry-standard ESD precautions should be used at all times.
Electrical and Mechanical Specifications
The absolute maximum ratings of the AAT4616A are provided in
Table 2. The recommended operating conditions are specified in
Table 3, and electrical specifications are provided in Table 4.
Typical performance characteristics of the AAT4616A are
illustrated in Figures 3 through 14.
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Table 3. Recommended Operating Conditions
Parameter Symbol Minimum Typical Maximum Units
Input voltage VIN 2.4 5.5 V
High-level Input voltage VON(H) 1.4 V
Low-level Input voltage VON(L) 0.5 V
Operating temperature TA 40 +85 ºC
Table 4. AAT4616A Electrical Specifications (Note 1)
(VIN = 5 V, TA = 40 °C to +85 °C [Typical Values are at TA = 25 °C], Unless Otherwise Noted)
Parameter Symbol Test Condition Min Typical Max Units
Input voltage VIN 2.4 5.5 V
Operating quiescent current IQ VIN = 5 V, ON/ON = Active, IOUT = 0 A 10 25 µA
Off supply current IQ(OFF) ON/ON = Inactive, VIN = 5.5 V 0.01 1 µA
Off switch current ISD(OFF) ON/ON = Inactive, VIN = 5.5 V, VOUT = 0 V 0.01 1 µA
Under-Voltage Lockout VUVLO Rising edge, 1% Hysteresis 1.8 2.4 V
UVLO hysteresis VUVLO_HYS 10 mV
On resistance RDS(ON) VIN = 5.0 V, TA = 25 °C 130 180 m
VIN = 3.0 V, TA = 25 °C 150 230
On-resistance temperature coefficient TCRDS 2800 ppm/°C
Current limit ILIM RSET = 35 k, VOUT = VIN0.5 V 0.67 0.75 0.83 A
Minimum current limit ILIM(MIN) 300 mA
ON/ON input low voltage VON(L) VIN = 2.4 V to 5.5 V 0.5 V
ON/ON input high voltage VON(H) VIN = 2.4 V to 5.5 V 1.4 V
ON/ON input leakage ION(SINK) VON = 5.5 V 0.01 1 µA
Current limit response time tRESP VIN = 5 V 2 µs
Turn-on time tON VIN = 5 V, RLOAD = 10 4 7 µs
Turn-off time tOFF VIN = 5 V, RLOAD = 10 8 10 µs
Fault flag blanking time tBLANK 4 ms
Fault flag logic low output VFLT(L) IFLT(SINK) = 1 mA 0.4 V
Fault flag logic high leakage current IFLT(SINK) 0.03 1 µA
Over-temperature shutdown threshold TSD VIN = 5 V 140 °C
Over-temperature shutdown hysteresis TSD_HYS 15 °C
Note 1: Performance is guaranteed only under the conditions listed in this Table.
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Typical Performance Characteristics
Figure 3. Quiescent Current vs Temperature
(VIN = 5.0 V)
Figure 5. Quiescent Current Voltage
(TA = 25 °C)
Figure 7. RDS(ON) vs Temperature
Figure 4. Current Limit vs Output Voltage
(VIN = 5.0 V, TA = 25 °C, RSET = 34.8 k)
Figure 6. Off-Switch Current vs Temperature
(VIN = 5.0 V)
Figure 8. RSET vs ILIM (TA = 25 °C)
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Typical Performance Characteristics
Figure 9. ON(ON) Threshold vs Input Voltage
Figure 11. Figure 10. AAT4616AIPU-1 Turn-Off
(RL = 10 , CL = 0.47 µF)
Figure 13. Output Short Response
(VIN = 5.0 V)
Figure 10. AAT4616AIPU-1 Turn-On
(RL = 10 , CL = 0.47 µF)
Figure 12. Short Circuit Through 0.3
(VIN = 5.0 V)
Figure 14. Fault Blanking Time
(VIN = 5.0 V)
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Figure 15. AAT4616A Functional Block Diagram
Functional Description
The AAT4616A is a single channel current limiting load switch
that is intended to protect against short circuit and over-current
events by current limiting to a preset level. This device also
provides a reverse current blocking feature, on/off enable
control, and a fault flag to notify a system controller of an over-
current, short circuit or over-temperature event.
In the event of a load current that exceeds a user-programmed
current limit level (ILIM), a high speed current limit loop limits
the current in a microsecond and resets to low impedance once
the short circuit condition is removed.
The AAT4616A is internally protected from thermal damage by
an over-temperature detection circuit. If the die temperature
reaches the internal thermal limit, the power device is switched
off until the die temperature cools to a level below the thermal
limit threshold. This device may operate in a thermal cycling
state indefinitely or until the over-current condition is removed.
The AAT4616A operates with input voltages ranging from 2.4 V
to 5.5 V which, along with its extremely low operating current,
make it ideal for battery-powered applications. In cases where
the input voltage drops to below 2.4 V, the AAT4616A MOSFET
is protected from entering the saturated region of operation by
being automatically shut down by the UVLO circuit.
Current limit or over-temperature conditions are reported by the
open drain FAULT output. A 4 ms blanking interval prevents
false reporting during the charging of a capacitive load, which
typically occurs during device turn-on, but may also occur
during a port hot plug-in event. The AAT4616A is ideally suited
for protection of peripheral ports such as USB, RS232, and
parallel ports.
Reverse Current Blocking
The reverse current blocking feature prevents current flowing
from OUT to IN when the device is disabled. When the device is
enabled, the electrical characteristics between IN and OUT are
still similar to an ideal switch, and current can flow in either
direction.
Application Information
Setting Current Limit
The AAT4616A current limit can be set by an external resistor
(RSET) connected from the SET pin to GND. RSET can be
calculated by the following equation:
where ILIM is in mA and RSET in k.
Table 5 summarizes resistor values for current limit settings.
Use 1% tolerance metal film resistors to program the desired
current limit setting. Figure 16 shows the output current versus
output voltage with RSET equal to 34.8 k.
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Table 5. Recommended 1% Tolerance Metal Film Resistors RSET
for Current Limit
RSET (k
) Current Limit (mA)
86.6 300
51 500
34.8 750
26.1 1000
21.5 1200
18.2 1400
16.5 1600
Figure 16. Current Limit vs Output Voltage with 34.8 k RSET
Input Capacitor
The input capacitor CIN protects the power supply from current
transients generated by the load attached to the AAT4616A.
When a short circuit is suddenly applied to the output of the
AAT4616A, a large current, limited only by the RDS(ON) of the
MOSFET, flows for less than 1 µs before the current limit
circuitry activates. In this event, a moderately sized CIN
dramatically reduces the voltage transient seen by the power
supply and by other circuitry upstream from the AAT4616A.
The extremely fast short-circuit response time of the AAT4616A
reduces the size requirement for CIN. CIN should be located as
close to the device VIN pin as practically possible. Ceramic,
tantalum, or aluminum electrolytic capacitors are appropriate
for CIN. There is no specific capacitor Equivalent Series
Resistance (ESR) requirement for CIN. 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.
Output Capacitor
To ensure stability while the current limit is active, a low
capacitance (approximately 0.47 µF) is required. No matter how
large the output capacitor, the output current is limited to the
value set by the AAT4616A current limiting circuitry, so very
large output capacitors can be used.
For example, USB ports are specified to have at least 120 µF of
capacitance downstream from their controlling power switch.
The current limiting circuit allows an output capacitance of
1000 µF or more without disturbing the upstream power supply.
ON/ON (Enable Input)
In many systems, power planes are controlled by integrated
circuits that run at lower voltages than the power planes,
themselves. The enable input (ON/ON) of the AAT4616A has low
and high threshold voltages that accommodate this condition.
The threshold voltages are compatible with 5 V TTL and
2.5 V 5 V CMOS systems.
Both active high and active low options are available.
Connecting to Capacitive Load
When the AAT4616A is switched onto a capacitive load, the
device charges the output capacitive load at a rate no greater
than the current limit setting.
FAULT Output
The FAULT Flag FLT is provided to alert the system if an
AAT4616A load is not receiving sufficient voltage to operate
properly. If current limit or over-temperature circuits in any
combination are active for more than approximately 4 ms, the
FAULT Flag is pulled to ground through an approximately 100
resistor.
The filtering of voltage or current transients of less than 4 ms
prevents capacitive loads connected to the AAT4616A output
from activating the FAULT Flag when they are initially attached.
Pull-up resistances of 10 k to 100 k are recommended.
Since FLT is an open-drain terminal; it may be pulled up to any
unrelated voltage less than the maximum operating voltage of
5.5 V, allowing for level shifting between circuits.
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Thermal Considerations
Since the AAT4616A has internal current limit and over-
temperature protection, junction temperature is rarely a concern.
However, if the application requires large currents in a hot
environment, it is possible that temperature, rather than current
limit, is the dominant regulating condition. In these applications,
the maximum current available without risk of an over-
temperature condition must be calculated. The maximum
internal temperature while the current limit is inactive can be
calculated using the following equation:
(1)
Where:
IMAX is the maximum current required by the load.
RDS(ON)(MAX) is the maximum rated RDS(ON) of the AAT4616A at
high temperature.
RθJA is the thermal resistance between the AAT4616A die and
the board onto which it is mounted.
TA(MAX) is the maximum temperature that the PCB under the
AAT4616A would be if the AAT4616A were not dissipating
power.
Rearranging equation (1) to solve for IMAX:
(2)
Note that TJ(MAX) has been replaced by TSD(MIN), the minimum
temperature required to activate the over-temperature
protection feature of the AAT4616A. With the typical
specification of 140 °C, a safe minimum value to use would be
125 °C.
For example, if an application is specified to operate in 50 °C
environments, the PCB operates at temperatures as high as
85 °C. The application is sealed and its PCB is small, causing
RθJA to be approximately 85 °C/W. Using equation (2):
Evaluation Board Information
The AAT4616A Evaluation Board schematic diagram is provided
in Figure 17. The PCB layer details are shown in Figure 18, and
Table 6 lists the Evaluation Board Bill of Materials (BOM).
Figure 17. AAT4616A Evaluation Board Schematic
Table 6. AAT4616A Evaluation Board Bill of Materials (BOM)
Component Part Number Description Manufacturer
U1 AAT4616AIPU-T1 Current Limited Load Switch Skyworks
C1 GRM188R71C105K Ceramic capacitor, 1 µF, 0603 X7R, 16 V, 10% Murata
C2 GRM188R71C474K Ceramic capacitor, 0.47 µF, 0603 X7R, 16 V, 10% Murata
RSET Chip Resistor Resistor, 34.8 k, 1/16 W, 1%, 0603 SMD Vishay
R2 Chip Resistor Resistor, 100 k, 1/16 W, 1%, 0603 SMD Vishay
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Figure 18. AAT4616A Evaluation Board Layer Details
Package Information
Package dimensions for the TDFN22-6 are shown in Figure 19,
and tape and reel dimensions are provided in Figure 20.
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Figure 19. AAT4616A TDFN22-6 Package Dimensions
Figure 20. AAT4616A Tape and Reel Dimensions
DATA SHEET • AAT4616A HIGH PRECISION ADJUSTABLE CURRENT LIMITED LOAD SWITCH WITH FAULT FLAG
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Ordering Information
Model Name Enable Input Package Marking
(Note 1)
Manufacturing Part Number
(Note 2) Evaluation Board Part Number
AAT4616A Adjustable Current Limited
Load Switch with Fault Flag
Active High TDFN22-6 R9XYY AAT4616AIPU-1-T1 AAT4616AIPU-1-EVB
Active Low TDFN22-6 U4WBF AAT4616AIPU-T1 AAT4616AIPU-EVB
Note 1: XYY = assembly and date code.
Note 2: Sample stock is generally held on part numbers listed in BOLD.
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