PRODUCT DATASHEET
AAT2601178
Total Power Solution for Portable Applications
Constant Current Mode Charge Current
vs. ISET Resistor
(VIN = 5V; VBAT = 3.6V)
ISET Voltage vs. Battery Voltage
(CHGIN = 5.0V, RISET = 1.24kΩ)
1.4
1.2
1
1400
1200
1000
800
600
400
200
0
0.8
0.6
0.4
0.2
0
2.5
2.9
3.3
3.7
4.1
4.5
0.1
1
10
100
ISET Resistor (kΩ)
Battery Voltage (V)
Figure 5: Constant Current Mode Charge ICH_CC Setting vs. ISET Resistor
and ISET Voltage vs. Battery Voltage.
Reverse Battery Leakage
CHGIN Bypass Capacitor Selection
The AAT2601 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 AAT2601’s
under voltage-lockout (UVLO) voltage, or when CHGIN
drops below VBAT, the AAT2601 automatically reconfig-
ures its power switches to minimize current drain from
the battery.
CHGIN is the power input for the AAT2601 battery char-
ger. The battery charger is automatically enabled when-
ever a valid voltage is present on CHGIN. In most appli-
cations, CHGIN is connected to either a wall adapter or
USB port. Under normal operation, the input of the char-
ger will often be “hot-plugged” directly to a powered USB
or wall adapter cable, and supply voltage ringing and
overshoot may appear at the CHGIN pin. A high quality
capacitor connected from CHGIN to G, placed as close as
possible to the IC, is sufficient to absorb the energy.
Wall-adapter powered applications provide flexibility in
input capacitor selection, but the USB specification pres-
ents limitations to input capacitance selection. In order
to meet both the USB 2.0 and USB OTG (On The Go)
specifications while avoiding USB supply under-voltage
conditions resulting from the current limit slew rate
(100mA/μs) limitations of the USB bus, the CHGIN
bypass capacitance value must be between 1μF and
4.7μF. Ceramic capacitors are often preferred for bypass-
ing due to their small size and good surge current rat-
ings, but care must be taken in applications that can
encounter hot plug conditions as their very low ESR, in
combination with the inductance of the cable, can create
a high-Q filter that induces excessive ringing at the
CHGIN pin. This ringing can couple to the output and be
mistaken as loop instability, or the ringing may be large
enough to damage the input itself. Although the CHGIN
pin is designed for maximum robustness and an absolute
Adapter Power Indicator (ADPP)
This is an open drain output which will pull low when
VCHGIN > 4.5V. When this happens, depending on the sta-
tus of the USE_USB pin, the charge current will be reset
to the default ISET values or I2C programmed values.
Charge Status Output (STAT)
The AAT2601 provides battery charging status via a sta-
tus pin. This pin is a buffered output with a supply level
up to the LDO1 output (PowerDigital). The status pin can
indicate the following conditions:
Event Description
STAT
No battery charging activity
Battery charging
Low (to GND)
High (to VOUT1
)
Charging completed
Low (to GND)
Table 2: Charge Status Output (STAT).
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2601.2008.01.1.0
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