AAT2601 Analogic Corporation, AAT2601 Datasheet - Page 25

• Manufacturer Part Number: AAT2601
• Manufacturer: Analogic Corporation

Reverse Battery Leakage
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 V
ures its power switches to minimize current drain from
the battery.
Adapter Power Indicator (ADPP)
This is an open drain output which will pull low when
V
tus of the USE_USB pin, the charge current will be reset
to the default ISET values or I
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:
2601.2008.01.1.0
CHGIN
1400
1200
1000
800
600
400
200
No battery charging activity
0
Constant Current Mode Charge Current
0.1
> 4.5V. When this happens, depending on the sta-
Table 2: Charge Status Output (STAT).
Event Description
Charging completed
Battery charging
BAT
, the AAT2601 automatically reconfig-
vs. ISET Resistor
(V
IN
ISET Resistor (kΩ Ω )
1
Figure 5: Constant Current Mode Charge I
= 5V; V
BAT
= 3.6V)
2
C programmed values.
10
High (to V
and I
Low (to GND)
Low (to GND)
STAT
SET
100
w w w . a n a l o g i c t e c h . c o m
OUT1
Voltage vs. Battery Voltage.
)
Total Power Solution for Portable Applications
CHGIN Bypass Capacitor Selection
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
CH_CC
Setting vs. I
1.4
1.2
0.8
0.6
0.4
0.2
1
0
2.5
ISET Voltage vs. Battery Voltage
PRODUCT DATASHEET
2.9
(CHGIN = 5.0V, R
SET
Resistor
Battery Voltage (V)
3.3
AAT2601178
ISET
3.7
= 1.24kΩ Ω )
4.1
25
4.5