AAT3673 Datasheet, PDF (17/28 Pages) Skyworks Solutions Inc. – 1.6A Dynamic Battery Charger and Power Manager

DATA SHEET
AAT3673
1.6A Dynamic Battery Charger and Power Manager
If the desired end of charge termination current level is
not listed in Table 3, the TERM resistor value may be
calculated by the following equation:
2V
I_{CH_TERM} = K_{I_TERM} · _RTERM
or
2V
R_TERM = K_{I_TERM} · _{ICH_TERM}
K_{I_TERM} = 2000 (typical)
When the input supply is disconnected, the charger also
automatically enters power-saving sleep mode.
Consuming less than 1μA in sleep mode, the AAT3673
minimizes battery drain when not charging. This feature
is particularly useful in applications where the input sup-
ply level may fall below the usable range of the charge
reduction control or under-voltage lockout level. In such
cases where the AAT3673 input voltage drops, the
device will enter the sleep mode and automatically
resume charging once the input supply has recovered
from its fault condition.
Dynamic Current Regulation
There are two possible configurations where the system
load current and charge current are dynamically con-
trolled. In the first case, the ADP-BAT switch and the
BAT-OUT switch are enabled, and the ADP-OUT switch is
disabled. Under this condition, the adapter input current
is set by the R_SET resistor (fast charge current setting,
I_{CH_CC}) and is split between the system load (I_BAT-OUT) and
the battery charge current (I_BAT). The charge current is
dynamically adjusted as the system load varies in order
to maintain the adapter input current.
I_{CH_CC} = I_BAT + I_BAT-OUT
For example: If R_SET = 57.6kΩ, the fast charge current
is set for 1A. For a system load of 0mA, the battery
charge current is 1A. As the system load is increased
the battery charge current is reduced, until the system
load is equal to 1A and the battery charge current is 0A.
Further increases in the system load will result in the
battery supplying the balance of the current; a system
load of 1.2A requires the battery to supply 0.2A.
In the second case, the ADP-BAT switch, the BAT-OUT
switch and the ADP-OUT switch are all enabled. Under
this condition, the adapter input current is limited inter-
nally to 1.6A minimum (I_{LIM_ADP}) and is split between the
system load (I_ADP-OUT) and the battery charge current
(I_{CH_CC}). The charge current is dynamically adjusted as
the system load varies in order to maintain the adapter
input current at or below the 1.6A minimum.
I_{LIM_ADP} ≥ I_{CH_CC} + I_ADP-OUT
For example: If R_SET = 57.6kΩ, the fast charge current
is set for 1A. For a system load of 0mA, the battery
charge current is 1A and the adapter current is less than
1.6A. As the system load is increased the battery charge
current is 1A, until the system load is equal to 0.6A and
the adapter input current is 1.6A. Increasing the system
load above 0.6A causes the battery charge current to be
reduced, until the system load is equal to 1.6A and the
battery charge current is 0A. Further increases in the
system load will result in the battery supplying the bal-
ance of the current; a system load of 1.8A requires the
battery to supply 0.2A.
Over-Voltage Protection
In normal operation, an N-channel MOSFET acts as a
slew-rate controlled load switch, connecting and discon-
necting the power supply from ADP to BYP. A low resis-
tance MOSFET is used to minimize the voltage drop
between the voltage source and the charger and to
reduce the power dissipation. When the voltage on the
input exceeds the over-voltage trip point of 6.75V, the
device turns off the internal switch which disconnects the
charger from the abnormal input voltage, therefore pre-
venting any damage to the charger. The OVP turn-on and
release delay times for the AAT3673-1/-2/-3 are 150μs
and 130μs respectively, while in the AAT3673-4/-5/-6
these delay times are extended to 80ms typically. If an
over-voltage condition is applied at the time of the device
enable, then the load switch will remain OFF.
OVP Under-Voltage Lockout (UVLO)
The AAT3673 OVP circuitry has a fixed 3.1V under-
voltage lockout level (UVLO). When the adapter input
voltage is less than the UVLO threshold level, the
MOSFET load switch is turned off. A 100mV of hysteresis
is included to ensure circuit stability.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
201881B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
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