AAT3663_08 Datasheet, PDF (16/23 Pages) Advanced Analogic Technologies – 1A Linear Li-Ion Battery Charger for Single and Dual Cell Applications

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PRODUCT DATASHEET
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.
Programmable Charge
Termination Current
The AAT3663 is designed with a default charge termina-
tion current set to 10 percent of the programmed 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 voltage
charging mode drops to the charge termination thresh-
old 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 termination current levels based on a
percentage of the programmed fast charge current are
shown in Figure 3.
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
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.
Battery Charge Status Indication
The AAT3663 indicates the status of the battery under
charge using three status LED driver outputs. These
three LEDs can indicate simple functions such as input
power present, no battery charge activity, battery charg-
ing, 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 dis-
play LEDs if a user simply wants to have a single LED to
show “charging” or “not charging”. This can be accom-
plished by just using the STAT1 pin and a single LED.
Using two LEDs and both STAT pins simply gives the user
more information for the various charging states. Refer
to Table 2 for LED display definitions.
Event Description
Charge enabled without battery
Battery charging
Charging completed
Fault
STAT1
Flash¹
ON
OFF
OFF
STAT2
Flash¹
OFF
ON
OFF
Table 2: LED Status Indicator Truth Table.
1. Flashing rate depends on output capacitance.
16
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3663.2008.01.1.2