AAT3690 Datasheet, PDF (12/20 Pages) Advanced Analogic Technologies – 1.0A USB Port/Adapter Lithium-Ion/Polymer Battery Charger

AAT3690
1.0A USB Port/Adapter
Lithium-Ion/Polymer Battery Charger
Application Information
AC Adapter / USB System Power Charging
Adapter Mode
In the adapter mode, constant current charge lev-
els up to 1.0A can be programmed by the user. The
AAT3690 system control will always select the
adapter input over the USB supply input whenever
adapter voltage is present on the ADP pin. The
AAT3690 will operate from the adapter input over a
4.0V to 5.5V range.
The constant current fast charge current for the
adapter input mode is set by the R_SETADP resistor
connected between ADPSET and ground. Refer to
Table 1 for recommended R_SETADP values for a
desired constant current charge level. The precise
charging function in the adapter mode may be read
from the status LEDs. Please refer to the Battery
Charge Status Indication discussion in this
datasheet for further details.
Thermal Loop Control
Due to the integrated nature of the linear charging
control pass device for the adapter mode, a special
thermal loop control system has been employed to
maximize charging current under all operating con-
ditions. The thermal management system meas-
ures the internal circuit die temperature and
reduces the fast charge current when the device
exceeds a preset internal temperature control
threshold. Once the thermal loop control becomes
active, the fast charge current is initially reduced by
a factor of 0.44.
The initial thermal loop current can be estimated by
the following equation:
I_TLOOP = I_CC · 0.44
The thermal loop control re-evaluates the circuit die
temperature every three seconds and adjusts the
fast charge current back up in small steps to the full
fast charge current level or until an equilibrium cur-
rent is discovered and maximized for the given
ambient temperature condition. In the manner the
thermal loop controls the system charge level, the
AAT3690 will always provide the highest level of
constant current in the fast charge mode possible
for any given ambient temperature condition.
Adapter Input Charge Inhibit and Resume
The AAT3690 has an under-voltage lockout and
power on reset feature so that if the input supply to
the adapter pin drops below the UVLO threshold
the charger will suspend charging and shut down.
When power is re-applied to the adapter pin or the
UVLO condition recovers and V_ADP > V_BAT, the sys-
tem charge control will assess the state of charge
on the battery cell and will automatically resume
charging in the appropriate mode for the condition
of the battery.
USB Mode
The AAT3690 provides an input for intelligent USB
charging. When no voltage is present on the
adapter input pin, the charge controller will auto-
matically switch to accepting power from the USB
input. The USB charge may be user programmed
to any level between 50mA and 1A by selecting the
appropriate resistor values for R_SETUSB. Refer to
Table 1 for recommended R_SETUSB values for the
desired USB input constant current charge levels.
USB Charge Reduction
In many instances, product system designers do
not know the real properties of a potential USB port
used to supply power to the battery charger.
Typically, powered USB ports found on desktop
and notebook PCs should supply up to 500mA. In
the event a USB port being used to supply the
charger is unable to provide the programmed fast
charge current or if the system under charge must
also share supply current with other functions, the
AAT3690 will automatically reduce USB fast
charge current to maintain port integrity and protect
the host system.
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3690.2007.01.1.2