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PDF AAT4620 Data sheet ( Hoja de datos )
| Número de pieza | AAT4620 | |
| Descripción | PCMCIA Current Limit Interface and Capacitor Charger | |
| Fabricantes | AAT | |
| Logotipo |  |
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General Description
The AAT4620 SmartSwitch is a current limited P-
channel MOSFET power switch designed for high-
side load-switching applications in PCMCIA
GSM/GPRS/3G modem cards. Used in conjunc-
tion with a super capacitor, the AAT4620 will
ensure that the power ratings of the PCMCIA host
are not exceeded at any time. Featuring two inde-
pendent, programmable current limits and a power
loop, the AAT4620 can ensure that the super
capacitor can be charged without exceeding PCM-
CIA 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 AAT4620
also incorporates a System READY function which
can advise the system that the super capacitor is
fully charged and ready for use. Adjustable hys-
teresis is provided with the addition of an external
resistor. The quiescent supply current is typically a
low 40µA. In shutdown mode, the supply current
decreases to less than 1µA.
The AAT4620 is available in a thermally enhanced,
Pb-free, 12-pin TSOPJW package and is specified
over the -40°C to 85°C temperature range.
AAT4620
PCMCIA Current Limit Interface
and Capacitor Charger
Features
SmartSwitch™
• VIN Range: 3.0V to 5.5V
• Dual Independent Current Limits
— 100mA 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 RDS(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
• 12-Pin TSOPJW Package
Applications
• CF Card Port Power Protection
• Express Card GSM/GPRS/3G Modems
• Hot Swap Supplies
• PCMCIA Card GSM/GPRS/3G Modems
• Personal Communication Devices
Typical Application
V CC
ENSUPERCAP
EN OPERATION
VCC
EN IL
Under-
Voltage
Lockout
Reverse
Blocking
Over-Temp
Protection
Power
Loop
EN IU
1.2V
Reference
GND
Current
Limit
Control
RHYS
OUT
RDY
100kΩ
To Load
To μC
ISETL
ISETU
RSETU
RSETL
SuperCap
4620.2007.04.1.1
1
1 page  
Typical Characteristics
Output Current vs. Output Voltage
(RSETU = 383kΩ, 25°C)
0.40
VIN = 3.3V
0.30
0.20
0.10 VIN = 5V
0.00
0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3 3.3
Output Voltage (V)
Reverse Off-Switch Current vs. Temperature
(ENUB = ENLB = VCC; VIN = 0V)
100
10
VOUT = 5V
1
0.1 VOUT = 3.3V
0.01
-40
-20
0 20 40 60 80
Temperature (°C)
100 120
Off-Supply Current vs. Temperature
(ENUB = ENLB = VCC; VOUT = Open)
10
VIN = 5V
1
0.1
VIN = 3.3V
0.01
-40
-20
0 20 40 60 80
Temperature (°C)
100 120
AAT4620
PCMCIA Current Limit Interface
and Capacitor Charger
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
0
RSET vs. ILIM
(25°C)
VIN = 3.3V
VIN = 5V
200 400 600 800 1000 1200 1400 1600
RSET (kΩ)
Off-Switch Current vs. Temperature
(ENUB = ENLB = VCC; VOUT = 0V)
100
10
VIN = 5V
1
0.1
0.01
-40
-20
VIN = 3.3V
0 20 40 60
Temperature (°C)
80
100 120
4620.2007.04.1.1
5
5 Page 
ILOAD vs. RSETU and RSETL
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.10
0.30
0.50
0.70
0.90
1.10
1.30
1.50
RSETU and RSETL (MΩ)
Figure 1: Calculated Current Limit RSET
Characteristic.
System Ready Hysteresis (RHYS) and
System Ready (RDY)
In internal comparator senses the output voltage
and delivers a ready signal to the external micro
controller when the output voltage reaches 98% of
the final value (VCC). The comparator hysteresis is
programmed by a resistor from the RHYS pin to
ground. The RHYS voltage determines the hys-
teresis voltage and is equal to the RHYS source
current (1µA) times the RHYS resistance.
VHYST = RHYS · 1μA
= 200kΩ · 1μA
= 0.2V
The system ready pin (RDY) is an open drain out-
put that switches low when the output voltage
reaches 98% of the input voltage. It requires an
external pull up resistor tied to the input voltage
with a typical value of 100kΩ.
Power Loop
The AAT4620 power loop limits the load current in
the event that the device power dissipation becomes
excessive. The AAT4620 power loop regulates the
die temperature to 100°C, decreasing the load cur-
rent in increments of 1/32 of the current limit set point
when the die temperature reaches 100°C. When the
AAT4620
PCMCIA Current Limit Interface
and Capacitor Charger
die temperature exceeds 100°C it decreases the
load current by 1/32 of the current limit set point. If
die temperature is less than 100°C, it increases the
load current in increments of 1/32 of the current limit
set point until the set current limit point is reached or
the die temperature exceeds 100°C.
The delay time between die temperature measure-
ments varies depending on the load current limit
set point. The delay ranges from 1ms for a 75mA
current limit set point to 8ms for a 1.5A current limit
set point.
For the condition where there is no current limit set
point (shorting RSETU or RSETL to ground) the soft
start increments the current limit is 1/32 steps of
1.2A until the current reaches 1.2A, at which point
the power MOSFET turns on fully. At this point, the
current is limited by the RDS(ON) of the power MOS-
FET and other series resistance. The Power Loop
and Over-Temperature Loop then takes control to
limit the current until the output voltage has fully
charged.
Over-Temperature Protection
If the die temperature rate of rise is fast enough to
exceed the power loop regulated temperature,
over-temperature shutdown disables the device.
The over-temperature threshold is 145°C. After
over-temperature shutdown, soft start is initiated
once the die temperature drops to 130°C.
Short Circuit Protection
The series pass power MOSFET turns off com-
pletely after the output has charged to within 18mV
of the input voltage. This protects the device in the
event of a short circuit applied to the output.
Applying a short circuit or heavy load to the output
initiates the digital soft start where the current
ramps from zero to the final programmed value. The
power loop will be activated once the digital soft
start begins.
Under-Voltage Shutdown
Under-voltage lockout enables the device at 2.7V
typical with 100mV of hysteresis. The maximum
UVLO level is 3.0V.
4620.2007.04.1.1
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet AAT4620.PDF ] | |
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