AAT3663 Datasheet, PDF (14/22 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications

AAT3663
1A Linear Li-Ion Battery Charger
for Single and Dual Cell Applications
10000
1000
100
10
1
1
10
100
R_SET (kΩ)
Figure 2: Constant Charging Current vs. R_SET
Resistor Values.
If the desired charge current level is not listed in
Table 1, the R_SET resistor value can be found in
Figure 2 and calculated by the following equation:
Where:
R_SET
=
K
·
⎛V_ISET⎞
⎝ I_CC ⎠
K = K_{I_SET} = 900
V_ISET = 2V
I_CC = Fast charge constant current
Programmable Charge Termination
Current
The AAT3663 is designed with a default charge ter-
mination current set to 10 percent of the pro-
grammed fast charge constant current level. The
charge termination current (I_{CH_TERM}) may also be
user programmed to a level other than 10% of the
set fast charge current by connecting a set resistor
(R_TERM) between the TERM pin and ground.
When the charge current under the constant volt-
age charging mode drops to the charge termination
threshold the device halts charging and goes into
a sleep mode. The charger will remain in the sleep
mode until the battery voltage as sensed by the
BATS pin decreases to a level below the battery
recharge voltage threshold (V_RCH). Charge termi-
nation current levels based on a percentage of the
programmed fast charge current are shown in
Figure 3.
50
45
40
35
30
25
20
15
10
5
0
0
10
20
30
40
50
60
R_TERM (kΩ)
Figure 3: Charge Termination Current (% Value
of the Programmed Fast Charge Current) vs.
R_TERM Resistance.
If the desired charge termination current set resistor
(R_TERM) value is not shown in Figure 3, the value
may be determined by the following equation:
I_{CH_TERM}
=
15µA · R_TERM
2V
·
I_{CH_CC}
Where:
I_{CH_TERM} = Charge termination current level
I_{CH_CC} = Programmed fast charge constant current
level
R_TERM = TERM resistor value
Battery Charge Status Indication
The AAT3663 indicates the status of the battery
under charge using three status LED driver out-
puts. These three LEDs can indicate simple func-
tions such as input power present, no battery
charge activity, battery charging, charge complete
and charge fault.
Status Indicator Display
System charging status may be displayed using
one or two LEDs in conjunction with the STAT1 and
STAT2 pins on the AAT3663. These two pins are
simple open drain N-channel MOSFET switches to
connect the status LED cathodes to ground. It is
not necessary to use both display LEDs if a user
simply wants to have a single LED to show “charg-
ing” or “not charging”. This can be accomplished
14
3663.2007.10.1.0