AAT3683 Datasheet, PDF (13/24 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger

Application Information
Adapter or USB Power Input
Constant current charge levels up to 1A may be
programmed by the user when powered from a suf-
ficient input power source. The AAT3683 will oper-
ate from the adapter input over a 4.0V to 6.5V
range. The constant current mode fast charge cur-
rent for the adapter input is set by the R_SET resistor
connected between ISET and ground. Refer to
Table 4 for recommended R_SET values for a desired
constant current charge level.
Adapter Input Charge Inhibit and Resume
The AAT3683 has a UVLO and power on reset fea-
ture so that if the input supply to the ADP pin drops
below the UVLO threshold, the charger will sus-
pend charging and shut down. When power is re-
applied to the IN pin or the UVLO condition recov-
ers, the system 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.
Digital 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 operation 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_{CH_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. The thermal loop
AAT3683
1A Linear Li-Ion Battery Charger
controls the system charge level; therefore, the
AAT3683 will always provide the highest level of
constant current in the fast charge mode possible
for any given ambient temperature condition.
Enable / Disable
The AAT3683 provides an enable function to con-
trol the charger IC on and off. The enable (EN) pin
is internally pulled down. When pulled to a logic
high level, AAT3683 is enabled. When left open or
pulled to a logic low level, the AAT3683 will be shut
down. Charging will be halted regardless of the
battery voltage or charging state. When the device
is re-enabled, the charge control circuit will auto-
matically reset and resume charging functions with
the appropriate charging mode based on the bat-
tery charge state and measured cell voltage on the
BAT pin.
Programming Charge Current
The constant current mode charge level is user
programmed with a set resistor placed between the
ISET pin and ground. The accuracy of the constant
charge current, as well as the preconditioning trick-
le charge current, is dominated by the tolerance of
the set resistor used. For this reason, a 1% toler-
ance metal film resistor is recommended for the set
resistor function. The constant charge current lev-
els from 100mA to 1A may be set by selecting the
appropriate resistor value from Table 1.
Constant Charging
Current (mA)
100
200
300
400
500
600
700
800
900
1000
Set Resistor
Value (kΩ)
16.2
8.06
5.36
4.02
3.24
2.67
2.26
2
1.78
1.58
Table 1: R_SET Values.
3683.2007.06.1.0
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