The AAT4621 SmartSwitch is a current limited P-channel
MOSFET power switch designed for high-side load-
switching applications in PC Card GSM/GPRS/3G modem
cards. Used in conjunction with a super capacitor, the
AAT4621 will ensure that the power ratings of the
PCMCIA host are not exceeded at any time. Featuring
two independent, programmable current limits and a
power loop, the AAT4621 can ensure that the super
capacitor can be charged without exceeding PCMCIA
specifications. The current limit is set by two external
resistors allowing a ±10% current limit accuracy over
the normal operating temperature range. The switch can
be controlled from either of the two enable inputs and in
the off condition will block currents in both directions.
The AAT4621 also incorporates a System READY function
which can advise the system that the super capacitor is
fully charged and ready for use. Adjustable hysteresis is
provided with the addition of an external resistor. The
quiescent supply current is typically a low 40μA. In shut-
down mode, the supply current decreases to less than
1μA.
The AAT4621 is available in a thermally enhanced,
Pb-free 14-pin TDFN33 package and is specified over the
-40°C to 85°C temperature range.
PC Card Current Limit Interface and Capacitor Charger
Features
• V
IN
Range: 3.0V to 5.5V
• Dual Independent Current Limits
▪
75mA to 1200mA
▪
±10% Current Accuracy
▪
20°C Temperature Band
• Reverse Current Blocking Protection
• Power Loop
• Low Quiescent Current
▪
40μA Typical
▪
1.0μA Max with Switch Off
• 65mΩ Typical R
DS(ON)
at 3V
• Only 1.4V Needed for Enable Control Pin
• System READY Output with Externally Programmable
Hysteresis
• Under-Voltage Lockout
• Temperature Range: -40 to 85°C
• 14-Pin TDFN33 Package
Applications
•
•
•
•
•
Capacitor Charger
CF Card Port Power Protection
Express Card GSM/GPRS/3G Modems
PC Card GSM/GPRS Class 10/12 Modems
WiMAX Cards
Typical Application
VCC
V
CC
Reverse
Blocking
100kΩ
OUT
Over-Temp
Protection
To Load
Under-
Voltage
Lockout
EN IL
EN
SUPERCAP
EN
OPERATION
EN IU
1.2V
Reference
Current
Limit
Control
Power
Loop
RDY
To μC
ISETL
ISETU
GND
SuperCap
R
HYS
R
SETU
R
SETL
4621.2009.08.1.4
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1
PRODUCT DATASHEET
AAT4621
SmartSwitch
TM
Pin Descriptions
Pin #
1
2
3
4
5, 6, 7
8, 9, 10, 11
12
13
14
PC Card Current Limit Interface and Capacitor Charger
Symbol
RDY
RHYS
ISETU
ISETL
OUT
VCC
GND
EN IL
EN IU
Function
System ready pin. Open drain, active low, initiated when the capacitor is 98% charged.
System READY hysteresis. Connect a resistor to ground to set the System Ready comparator hysteresis.
Upper current limit set input. A resistor from I
SETL
to ground sets the maximum upper current limit for
the switch. Current limits can be set between 75mA and 1200mA. Connect to ground to disable current
limit.
Lower current-limit set input. A resistor from I
SETU
to ground sets the maximum lower current limit for
the switch. Current limit can be set between 75mA and 1200mA.
P-channel MOSFET drain connection. Connect to super capacitor from OUT to GND.
Input pins to the P-channel MOSFET source. Connect 1μF capacitor from VCC to GND.
Device ground connection.
Enable input. Active low enable with internal pull up. Also switches in the lower current limit initiating
the super capacitor to start charging.
Enable input. Active low enable with internal pull up. Also switches in the higher current limit to allow the
System to start functioning. Can be directly connected to System Ready for automatic enabling. When
both EN IL B and EN IU B are enabled, I
SETU
will be selected.
The exposed thermal pad (EP) must be connected to the board ground plane and Pin 12. The ground
plane should include a large exposed copper pad under the package for thermal dissipation (see pack-
age outline).
EP
EP
Pin Configuration
TDFN33-14
(Top View)
RDY
RHYS
ISETU
ISETL
OUT
OUT
OUT
1
2
3
4
5
6
7
14
13
12
EP
11
10
9
8
ENIU
ENIL
GND
VCC
VCC
VCC
VCC
2
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4621.2009.08.1.4
PRODUCT DATASHEET
AAT4621
SmartSwitch
TM
PC Card Current Limit Interface and Capacitor Charger
Absolute Maximum Ratings
1
Symbol
V
CC
V
EN
V
SET
, V
OUT
I
MAX
Description
VCC to GND
EN to GND
SET, OUT to GND
Maximum Continuous Switch Current
Value
-0.3 to 6
-0.3 to V
CC
+ 0.3
-0.3 to V
CC
+ 0.3
2.5
Units
V
V
V
A
Thermal Characteristics
Symbol
θ
JA
P
D
T
J
Description
Maximum Thermal Resistance
2
Maximum Power Dissipation
2
Operating Junction Temperature Range
Value
50
2
-40 to 150
Units
°C/W
W
°C
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. Mounted on an FR4 board.
4621.2009.08.1.4
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3
PRODUCT DATASHEET
AAT4621
SmartSwitch
TM
Electrical Characteristics
1
V
CC
= 3.0V to 5.5V, T
A
= -40°C to 85°C unless otherwise noted. Typical values are at T
A
= 25°C.
Symbol
V
CC
I
Q
I
QU0
I
Q(OFF)
I
SD(OFF)
V
UVLO
R
DS(ON)
I
LIMLACC
I
LIMUACC
I
LIM(MIN)
V
EN(L)
V
EN(H)
I
EN(SINK)
T
DEL(OFF)
V
RDY
V
RDYHYS
V
RDY(L)
I
RDY
OTMP
PC Card Current Limit Interface and Capacitor Charger
Description
Operation Voltage
Quiescent Current
Quiescent Current U
0
Off Supply Current
Off Switch Current
Under-Voltage Lockout
On-Resistance
Lower Current Limit Accuracy
Upper Current Limit Accuracy
Lower Minimum Current Limit
EN Input Low Voltage
EN Input High Voltage
EN Input Leakage
Turn-Off Delay Time
System READY Trip Threshold
System READY Hysteresis
System READY Voltage Low
RDY Leakage Current
Shutdown Temperature
Conditions
EN IL or EN IU = V
CC
, I
OUT
= 0, R
HYS
= 200kΩ
EN IL = V
CC
, EN IU = GND, I
OUT
= 0, I
SET
= GND,
R
HYS
= 200kΩ
EN IL = EN IU = V
CC
EN IL = EN IU = V
CC
, V
SUPERCAP
= 0
Rising edge, 1% hysteresis
V
CC
= 4.75V, R
SETL
= R
SETU
= 0k
V
CC
= 3.0V, R
SETL
= R
SETU
= 0k
R
SETL
= 249kΩ;
ΔT
A
≤
20°C
R
SETL
= 249kΩ
R
SETU
= 1.24MΩ;
ΔT
A
≤
20°C
R
SETU
= 1.24MΩ
V
CC
= 3.0V to 5.5V
V
CC
= 3.0V to 5.5V
2
V
EN
= 5.5V
V
CC
= 5V
V
OUT
rising, T
A
= 25°C
R
HYS
= 200kΩ
I
SINK
= 1mA
V
RDY
< 5.5V, V
OUT
< 98% of V
OUT
2
Min
3.0
Typ
40
40
0.4
0.4
2.7
50
65
200
200
1000
1000
75
Max
5.5
75
75
1.0
10
3.0
100
120
220
230
1100
1150
0.4
Units
V
μA
μA
μA
μA
V
mΩ
mA
mA
mA
V
V
μA
μs
% of V
OUT
mV
V
μA
°C
180
170
900
850
1.4
0.4
98
200
1.0
1.0
0.4
1.0
145
1. The AAT4621 is guaranteed to meet performance specification over the -40°C to 85°C operating temperature range and is assured by design, characterization and correlation
with statistical process controls.
2. For V
IN
outside this range consult the Typical EN Threshold curve.
4
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4621.2009.08.1.4
PRODUCT DATASHEET
AAT4621
SmartSwitch
TM
Typical Characteristics
Output Current vs. Output Voltage
(R
SETU
= 383kΩ, 25°C)
Ω
0.40
1.40
PC Card Current Limit Interface and Capacitor Charger
