AAT3601_08 Datasheet, PDF (25/37 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications

PRODUCT DATASHEET
AAT3601178
Total Power Solution for Portable Applications
Constant-Current Mode Charge Current
Trickle charge continues until the battery voltage reach-
es V_MIN. At this point the battery charger begins con-
stant-current charging. The current level default for this
mode is programmed using a resistor from the ISET pin
to ground. Once that resistor has been selected for the
default charge current, then the current can be adjusted
through I²C from a range of 40% to 180% of the pro-
grammed default charge current. Programmed current
can be set at a minimum of 100mA and up to a maxi-
mum of 1.44A. When the CHGIN_OK signal goes low, the
default I²C setting of 100% is reset. If the USE_USB
signal is high when this happens, the charge current is
reset to an internally set 100mA current until the micro-
controller sends another I²C signal to change the charge
current. (see I²C Programming section).
Constant-Voltage Mode Charge
Constant current charging will continue until the battery
voltage reaches the Output Charge Voltage Regulation
point V_{BAT_REG}. When the battery voltage reaches the regu-
lation voltage (V_{BAT_REG}), the battery charger will transition
to constant-voltage mode. V_{BAT_REG} is factory programmed
to 4.2V (nominal). Charging in constant-voltage mode will
continue until the charge current has reduced to the end
of charge termination current programmed using the I²C
interface (5%, 10%, 15%, or 20%).
Power Saving Mode
After the charge cycle is complete, the battery charger
turns off the series pass device and automatically goes
into a power saving sleep mode. During this time, the
series pass device will block current in both directions to
prevent the battery from discharging through the battery
charger.
The battery charger will remain in sleep mode even if the
charger source is disconnected. It will come out of sleep
mode if either the battery terminal voltage drops below
the V_RCH threshold, the charger ENBAT pin is recycled, or
the charging source is reconnected. In all cases, the bat-
tery charger will monitor all parameters and resume
charging in the most appropriate mode.
Temperature Sense (TS)
The TS pin is available to monitor the battery tempera-
ture. Connect a 10k NTC resistor from the TS pin to
ground. The TS pin outputs a 75μA constant current into
the resistor and monitors the voltage to ensure that the
battery temperature does not fall outside the limits
depending on the Temperature coefficient of the resistor
used. When the voltage goes above 2.39V or goes below
331mV, the charging current will be suspended.
Charge Safety Timer (CT)
While monitoring the charge cycle, the AAT3601 utilizes
a charge safety timer to help identify damaged cells and
to ensure that the cell is charged safely. Operation is as
follows: upon initiating a charging cycle, the AAT3601
charges the cell at 10% of the programmed maximum
charge until V_BAT > 2.8V. If the cell voltage fails to the
precondition threshold of 2.8V (typ) before the safety
timer expires, the cell is assumed to be damaged and
the charge cycle terminates. If the cell voltage exceeds
2.8V prior to the expiration of the timer, the charge cycle
proceeds into fast charge. Three timeout periods of 1
hour for Trickle Charge mode, 3 hours for Constant
Current Mode and 3 hours for Constant Voltage mode.
Mode
Time
Trickle Charge (T_K) Time Out
Trickle Charge (T_K) + Constant Current (T_C)
Mode Time Out
Constant Voltage (T_V) Mode Time Out
25 minutes
3 hours
3 hours
Table 1: Charge Safety Timer (CT) Timeout Period
for a 0.1μF Ceramic Timing Capacitor.
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
terminating the CT pin to ground or disabled using the
I²C bus. The CT pin should not be left floating or unter-
minated, as this will cause errors in the internal timing
control circuit. The constant current provided to charge
3601.2008.07.1.1
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