AAT3601_08 Datasheet, PDF (26/37 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications

PRODUCT DATASHEET
AAT3601178
Total Power Solution for Portable Applications
the timing capacitor is very small, and this pin is suscep-
tible 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 domi-
nated by the capacitance value, a 10% tolerance or bet-
ter ceramic capacitor is recommended. Ceramic capaci-
tor materials, such as X7R and X5R types, are a good
choice for this application.
Programming Charge Current (ISET)
The default constant current mode charge level is user
programmed with a set resistor placed between the ISET
pin and ground. The accuracy of the constant charge
current, as well as the preconditioning trickle charge
current, is dominated by the tolerance of the set resistor.
For this reason, a 1% tolerance metal film resistor is
recommended for the set resistor function. The constant
charge current levels from 100mA to 1A may be set by
selecting the appropriate resistor value from Table 2 and
Figures 6 and 7. The ISET pin current to charging cur-
rent ratio is 1 to 800. It is regulated to 1.25V during
constant current mode unless changed using I²C com-
mands. It can be used as a charging current monitor,
based on the equation:
I_CH
=
800
⋅
⎛
⎝
V_ISET⎞
R_ISET⎠
During preconditioning charge, the ISET pin is regulated
to 0.2V (Figure 6), but the equation stays the same.
During constant voltage charge mode, the ISET pin volt-
age will slew down and be directly proportional to the
battery current at all times.
Constant Charging
Current I_{CH_CC} (mA)
100
200
300
400
500
600
700
800
900
1000
Set Resistor
Value (kΩ)
10
4.99
3.32
2.49
2
1.65
1.43
1.24
1.1
1
Table 2: Constant Current Charge
vs. I_SET Resistor Value.
1400
1200
1000
800
600
400
200
0
0.1
1
10
100
ISET Resistor (kΩ)
Figure 6: Constant-Current Mode Charge
I_{CH_CC} Setting vs. I_SET Resistor.
Ω
1.4
1.2
1
0.8
0.6
0.4
0.2
0
2.5
2.9
3.3
3.7
4.1
4.5
Battery Voltage (V)
Figure 7: I_SET Voltage vs. Battery Voltage.
Reverse Battery Leakage
The AAT3601 includes internal circuitry that eliminates
the need for series blocking diodes, reducing solution
size and cost as well as dropout voltage relative to con-
ventional battery chargers. When the input supply is
removed or when CHGIN goes below the AAT3601’s
under-voltage lockout (UVLO) voltage, or when CHGIN
drops below V_BAT, the AAT3601 automatically reconfig-
ures its power switches to minimize current drain from
the battery.
Charge Status Output
(STAT and STAT_BAT)
The AAT3601 provides battery charging status via a sta-
tus pin. The STAT is active low open drain for driving and
LED. STAT_BAT is the same function as STAT pin but
with opposite polarity to be used as a μP flag. The status
pin can indicate the following conditions:
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3601.2008.07.1.1