AAT3783_12 Datasheet, PDF (11/20 Pages) Skyworks Solutions Inc. – 1-A Linear Li-Ion/Polymer Battery Charger with 28V Over-Voltage Protection

DATA SHEET
AAT3783
1-A Linear Li-Ion/Polymer Battery Charger with 28V Over-Voltage Protection
Charge Complete Voltage
Regulated Current
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
I = Max CC
Constant Voltage
Charge Phase
Constant Current Mode
Voltage Threshold
Trickle Charge and I = CC / 10
Termination Threshold
Figure 1: Current vs. Voltage Profile during Charging Phases.
Constant Current Charging
Battery cell preconditioning continues until the battery
voltage reaches the preconditioning voltage threshold,
V_MIN. At this point, the AAT3783 begins constant current
charging. The current level for this mode is programmed
using a single resistor from the ISET pin to ground. The
programmed current can be set at a minimum 100mA
up to a maximum of 1A.
Constant Voltage Charging
Constant current charging will continue until such time
that the battery voltage reaches the voltage regulation
point, V_{BAT_EOC}. When the battery voltage reaches V_{BAT_EOC},
the AAT3783 will transition to constant voltage mode.
The regulation voltage is factory programmed to a nom-
inal 4.2V and will continue charging until the charge
termination current is reached.
Charge Status Output
The AAT3783 provides battery charge status via a status
pin. This pin is internally connected to an N-channel
open-drain MOSFET, which can be used drive an external
LED. The status pin can indicate the following condi-
tions:
Event Description
No battery charging activity
Battery charging via adapter or USB port
Charging completed
STATUS
OFF
ON
OFF
Table 1: LED Status Indicator.
Thermal Considerations
The actual maximum charging current is a function of
the charge adapter input voltage, the battery charge
state at the moment of charge, the ambient tempera-
ture, and the thermal impedance of the package. The
maximum programmable current may not be achievable
under all operating parameters.
Over-Voltage Protection
In normal operation, a P-channel MOSFET acts as a
slew-rate controlled load switch, connecting and discon-
necting the power supply from IN to INCHR. A low resis-
tance MOSFET is used to minimize the voltage drop
between the voltage source and the charger and to
reduce the power dissipation. When the voltage on the
input exceeds the over-voltage trip point (internally set
by the factory or externally programmed by a resistor
connected to the OVP pin), the device immediately turns
off the internal P-channel FET which disconnects the
charger from the abnormal input voltage, therefore pre-
venting any damage to the charger. Simultaneously, the
fault flag is raise, alerting the system.
If an over-voltage condition is applied at the time of the
device enable, then the switch will remain OFF.
OVP Under-Voltage Lockout (UVLO)
The AAT3783 OVP circuitry has a fixed 3V under-voltage
lockout level (UVLO). When the input voltage is less than
the UVLO level, the MOSFET is turned off. 100mV of
hysteresis is included to ensure circuit stability.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
201903B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 27, 2012
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