AAT3691 Datasheet, PDF (10/18 Pages) Skyworks Solutions Inc. – Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package

DATA SHEET
AAT3691
Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package
Battery Charge Current
Regulated Current
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
I = Max CC
Constant Voltage
Charge Phase
Battery Voltage
Charge Complete Voltage
Charge Current
Battery Voltage
Constant Current Mode
Voltage Threshold
Trickle Charge and
Termination Threshold
I = CC/10
Time
Figure 1: Charge Current vs. Battery Voltage Profile during Charging Phases.
Battery charging commences only after the AAT3691
checks several conditions in order to maintain a safe
charging environment. The input supply must be above
the minimum operating voltage and the enable pin must
be low. When the battery is connected to the BAT pin and
the NOBAT pin indicates there is a battery connected,
the AAT3691 checks the condition of the battery and
determines which charging mode to apply. If the battery
voltage is below V_MIN, then the device begins trickle
charging by charging at 10% of the programmed con-
stant current. For example, if the programmed current is
500mA, then the trickle charge current is 50mA. Trickle
charging is a safety precaution for a deeply discharged
cell and will also reduce the power dissipation in the
internal series pass MOSFET when the input-output volt-
age differential is at its highest. Trickle charging contin-
ues until the battery voltage reaches V_MIN. At this point,
the AAT3691 begins constant current charging. The cur-
rent value for this mode is programmed by the external
resistors from the ADPSET and USBSET pin to ground.
Programmed current can be set from a minimum of
100mA up to a maximum of 1.6A for an ADP power
source, and from a minimum of 50mA up to a maximum
of 500mA for a USB power source. Constant current
charging continues until the battery voltage reaches the
voltage regulation point, V_{BAT_EOC}. When the battery volt-
age reaches V_{BAT_EOC} (typical 4.2V), the AAT3691 will
switch to constant voltage mode. Constant current
charge will continue until the charging current is reduced
to 10% of the programmed current. After the charge
cycle is complete, the AAT3691 turns off the series pass
device and automatically goes into standby mode.
During this time, the series pass device will block current
in both directions, therefore preventing the battery from
discharging through the IC.
The AAT3691 remains in standby mode until either the
battery terminal voltage drops below the V_RCH threshold,
the charger EN pin is recycled, or the charging source is
reconnected. In all cases, the AAT3691 will monitor all
parameters and resume charging in the most appropri-
ate mode.
Over-Voltage Protection
In normal operation an OVP switch acts as a slew-rate
controlled load switch, connecting and disconnecting the
power supply from ADP to ADPCH and USB to USBCH. A
low-resistance 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 6.75V (typical) voltage limit, the
device immediately turns off the internal OVP switch,
disconnecting the load from the abnormal voltage and
preventing damage to any downstream components.
On initial power-up with low and battery present, if
V_USB/ADP < V_UVLO (3V maximum), the OVP switch is held
off; if V_UVLO < V_USB/ADP < 6.75V (typical), the OVP switch
will turn on after a 130μs typical internal delay; if V_USB/ADP
rises above 6.75V (typical), the OVP switch is turned off
after a 0.5μs typical internal delay.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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201894B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 27, 2012