AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Constant Voltage Charging
When the battery voltage reaches V
CH
during con-
stant current mode, the AAT3680 transitions to con-
stant voltage mode. The regulation voltage is fac-
tory programmed: 4.1V and 4.2V are available to
support different anode materials in lithium-ion/poly-
mer cells. In constant voltage operation, the
AAT3680 monitors the cell voltage and terminates
the charging cycle when the voltage across R
SENSE
decreases to approximately 10mV.
Charge Cycle Termination, Recharge
Sequence
After the charge cycle is complete, the AAT3680
latches off the pass device and automatically enters
power-saving sleep mode. Either of two possible
conditions will bring the IC out of sleep mode: the
battery voltage at the BAT pin drops below V
RCH
(recharge threshold voltage) or the AAT3680 is reset
by cycling the input supply through the power-on
sequence. Falling below V
RCH
signals the IC that it
is time to initiate a new charge cycle.
Power On Reset
Power On Reset
UVLO
V
P
> V
UVLO
No
Shutdown
Shut Down
Mode
Mode
Yes
Temperature
Temperature
Fault
Fault
No
Temperature Test
TS > V
TS1
TS < V
TS2
Yes
Low Current
Conditioning
Low Current
Charge
Conditioning
(Trickle Charge)
Charge
Preconditioning Test
V
MIN
> V
BAT
Yes
No
Current
Current
Charging
Charging
Mode
Mode
Current Phase Test
V
CH
> V
BAT
Yes
No
Voltage
Phase Test
V
TERM
< I
BAT
R
SENSE
Yes
Voltage
Voltage
Charging
Charging
Mode
Mode
No
< V
RCH
Charge Complete
Charge Complete
Latch Off
Latch Off
Figure 1: AAT3680 Operational Flow Chart.
6
3680.2006.03.1.6
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
