AAT3680 Advanced Analogic Technologies, AAT3680 Datasheet - Page 5

• Manufacturer Part Number: AAT3680
• Description: Lithium-Ion Linear Battery Charge Controller
• Manufacturer: Advanced Analogic Technologies

Functional Block Diagram
Functional Description
The AAT3680 is a Linear Charge Controller
designed for one and two cell Lithium Ion or
Lithium Polymer batteries. It is a full-featured bat-
tery management system IC with multiple levels of
power savings, system communication and protec-
tion integrated inside. Refer to the block diagram
and flow chart in this section.
Cell Preconditioning
Before starting charging, the AAT3680 checks sev-
eral conditions in order to maintain a safe charging
environment. The input supply must be above the
minimum operating voltage, or undervoltage lock-
out threshold (V
begin. Also, the cell temperature, as reported by a
thermistor connected to TS pin, must be within the
proper window for safe charging. When these con-
ditions have been met, and a battery is connected
to the BAT pin, the AAT3680 checks the state of the
battery.
AAT3680 begins preconditioning the cell. This is
performed by charging the cell with 10% of the pro-
grammed constant-current amount. For example if
3680.2003.4.0.91
If the cell voltage is below V
UVLO
), for the charging sequence to
BAT
T2X
CSI
TS
V
P
Microcontroller
2x Trickle
Read Enable
Charge
Control
Current Loop
Comparator
Error Amp
Voltage
Temperature Sense
Power-On
Voltage Loop
Lithium-Ion Linear Battery Charge Controller
Comparator
Error Amp
Reset
MIN
V
REF
, the
Lock Out
Charge Status
Logic Control
Voltage
Under
Loop Select
MUX Driver
Over Current /
Short Circuit
Protection
the programmed charge current is 500mA, then the
preconditioning mode (trickle charge) current will be
50mA. Cell preconditioning is a safety precaution
for deeply discharged cells, and furthermore, limits
the power dissipation in the pass transistor when
the voltage across the device is largest.
AAT3680 features an optional T2X mode, which
allows faster trickle-charging at approximately two
times the default rate. This mode is selected by
connecting the T2X pin to V
ture fault is triggered, the fast trickle-charge will be
latched off, and the AAT3680 will continue at the
default 10% charge current.
Constant Current Charging
The cell preconditioning continues until the voltage
on the BAT pin reaches V
AAT3680 begins constant-current charging (fast
charging).
grammed using a current sense resistor R
between V
voltage across R
current control loop. The AAT3680 remains in con-
stant current charge mode until the battery reaches
the voltage regulation point, V
Status Generator
Microcontroller
LED Signal
Generator
MUX
P
and CSI pins. The CSI pin monitors the
Current level for this mode is pro-
DRV
STAT
V
SENSE
SS
to provide feedback for the
SS
MIN
. If an over-tempera-
CH
. At this point, the
.
AAT3680
SENSE
The
5