AAT3693 Advanced Analogic Technologies, Inc., AAT3693 Datasheet - Page 15

• Manufacturer Part Number: AAT3693
• Description: 1.6a Lithium-ion/polymer Battery Charger In 2.2x2.2 Tdfn
• Manufacturer: Advanced Analogic Technologies, Inc.

BatteryManager
The AAT3693 has a battery fault detector, which, when
used in conjunction with a 0.1μF capacitor on the CT pin,
outputs a 1Hz signal with 50% duty cycle at the STAT1
pin in the event of a timeout while in the trickle charge
mode.
Fault condition can be one of the following:
• Battery over voltage (OV)
• Battery temperature sense hot or cold
• Battery charge timer time-out
• Chip thermal shutdown
Status LED Setup
The LEDs should be biased with as little current as nec-
essary to create reasonable illumination; therefore, a
ballast resistor should be placed between the LED cath-
ode and the STAT pin. 2mA should be sufficient to drive
most low-cost green or red LEDs. It is not recommended
to exceed 8mA for driving an individual status LED. The
required ballast resistor values can be estimated using
the following formula:
Example:
Note: Red LED forward voltage (V
2mA.
Protection Circuitry
No-Battery Detection
After a battery is inserted and the AAT3693 detects the
present of the battery, the regular LED reporting indi-
cates the current charging status after 5-6 flashes. If the
battery is not detected, the status LEDs flash at a fre-
quency of 1Hz with ~50% duty cycle ratio continuously
on all options (AAT3693 AA, AB, … , BO and BT), except
AI and AJ.
The no-battery detection circuit is not integrated in the
AAT3693 AI or AJ. For these two options, the charger IC
treats the output ceramic capacitor as a battery. Since
the capacitance of the ceramic capacitor is very small,
the charge cycle is shortened and the STAT1 LED stays
off for a long time and on for a very short time. Therefore,
the STAT1 LED appears to always be OFF. In addition,
since the ceramic capacitor’s discharge cycle is much
longer than its charge cycle, the STAT2 LED appears to
3693.2009.04.1.1
R
BALLAST
R
BALLAST
=
(5.0V - 2.0V)
TM
=
2mA
(V
IN
I
- V
LED
FLED
F
) is typically 2.0V @
= 1.5kΩ
1.6A Lithium-Ion/Polymer Battery Charger in 2.2x2.2 TDFN
)
w w w . a n a l o g i c t e c h . c o m
remain ON because the brief OFF phase of the cycle is so
short that the human eye cannot perceive it.
If the thermal sensing TS pin is open it will be consid-
ered as no battery condition. Please refer to the "Battery
Temperature Fault Monitoring" section in order to deter-
mine the proper biasing for the TS pin.
Programmable Watchdog Timer
The AAT3693 contains a watchdog timing circuit to shut
down charging functions in the event of a defective bat-
tery cell not accepting a charge over a preset period of
time. Typically, a 0.1μF ceramic capacitor is connected
between the CT pin and ground. When a 0.1μF ceramic
capacitor is used, the device will time out a shutdown
condition if the trickle charge mode exceeds 25 minutes.
The time out timer will reset at start of the constant cur-
rent mode setting the time out to 1 hour (default). When
the device transitions to the constant voltage mode, the
timing counter is reset and will time out after an addi-
tional 2 hours if the charge current does not drop to the
charge termination level for options AE, AF, AG, AH, BM,
BN, BO and BP. For all other options (AA, AB, AC, AD, AI,
AJ, AK and AL) the timeout timer does not reset at every
charging mode and will time out in 3 hours (default).
Assuming: C
The CT pin is driven by a constant current source and will
provide a linear response to increases in the timing
capacitor value. Thus, if the timing capacitor were to be
doubled from the nominal 0.1μF value, the time-out
periods would be doubled. If the programmable watch-
dog timer function is not needed, it can be disabled by
connecting the CT pin to ground. The CT pin should not
be left floating or un-terminated, as this will cause errors
in the internal timing control circuit. The constant cur-
rent provided to charge the timing capacitor is very
small, and this pin is susceptible to noise and changes in
capacitance value. Therefore, the timing capacitor should
be physically located on the printed circuit board layout
as close as possible to the CT pin. Since the accuracy of
the internal timer is dominated by the capacitance value,
a 10% tolerance or better ceramic capacitor is recom-
mended. Ceramic capacitor materials, such as X7R and
X5R types are a good choice for this application.
Constant Current (CC) Timeout
Constant Voltage (CV) Timeout
Trickle Charge (TC) Timeout
Table 4: Watchdog Timer Time-out Options.
Mode
T
= 0.1μF and V
PRODUCT DATASHEET
IN
AAT3693
= 5.0V
Timer
Reset
Reset
Reset
Time
25
1
2
Minute
Units
Hour
Hour
15