AAT3673 Datasheet, PDF (14/28 Pages) Skyworks Solutions Inc. – 1.6A Dynamic Battery Charger and Power Manager

DATA SHEET
AAT3673
1.6A Dynamic Battery Charger and Power Manager
The internal arrangement of load switches and the charge
regulation device provide dynamic power sourcing to the
system load. If the system load exceeds the input current
supply from the input source, additional current can be
supplied from the battery cell. At all times, the device will
manage distribution of power between the source, the
battery and the system simultaneously in order to sup-
port system power needs and charge the battery cell with
the maximum amount of current possible. The AAT3673
has a unique internal charge current reduction control
loop that will prevent an input source from overload. In
the case of USB charging from a USB port V_USB supply,
there are two events which need to be guarded against.
The first is charging from a defective or inadequate USB
host supply; the second problem could arise if the pro-
grammed charge current plus the system supply demand
through the AAT3673 exceeds the ability of a given USB
port. In either case, the AAT3673 charge reduction (CHR)
loop will activate when the input source drops below the
V_{CHR_TH} threshold of 4.5V. The CHR loop will automatically
reduce the charge current to the battery until the supply
voltage recovers to a point above the V_{CHR_TH} threshold.
This unique feature protects the charger, system and
source supply in the event an adapter or power source
does not meet the programmed ADP charging mode cur-
rent demand. The resulting CHR system will permit the
charging of a battery cell with the maximum possible
amount of charge current for any given source.
During battery charging, the device temperature can
rise due to power dissipation within the charge current
control device and the load switches. In some cases, the
power dissipation in the device may cause the junction
temperature to rise up to its thermal shutdown thresh-
old. In the event of an internal over-temperature condi-
tion caused by excessive ambient operating temperature
or an excessive power dissipation condition, the AAT3673
utilizes a digitally controlled thermal loop system that
will reduce the charging current to prevent the device
from entering thermal shutdown. The digital thermal
loop will maintain the maximum possible battery charg-
ing current for the given set of input to output power
dissipation and ambient temperature conditions.
The digital thermal loop control is dynamic in the sense
that it will continue to adjust the battery charging current
as operating conditions change. The digital thermal loop
will reset and resume normal operation when the power
dissipation or over temperature conditions are removed.
Battery temperature and charge state are fully moni-
tored for fault conditions. In the event of an over voltage,
over-current, or over-temperature failure, the device will
automatically shut down, thus protecting the charging
device, control system, and the battery under charge. In
addition to internal charge controller thermal protection,
the AAT3673 also provides a temperature sense feedback
function (TS pin) from the battery to shut down the
device in the event the battery exceeds its own thermal
limit during charging. All fault events are reported to the
user by the simple status LED(s) which is (are) inter-
nally controlled by open drain NMOS switch(es).
Charging Operation
The AAT3673 has four basic modes for the battery
charge cycle: pre-conditioning/trickle charge, constant
current fast charge, constant voltage, and end of charge/
sleep state.
Battery Preconditioning
Before the start of charging, the AAT3673 checks sev-
eral conditions in order to assure a safe charging envi-
ronment. The input supply must be above the minimum
operating voltage, or under-voltage lockout threshold
(V_UVLO), for the charging sequence to begin. Also, the cell
temperature, as reported by a thermistor connected to
the TS pin from the battery, must be within the proper
window for safe charging. When these conditions have
been met and a battery is connected to the BAT pin, the
AAT3673 checks the state of the battery by sensing the
cell voltage. If the cell voltage is below the precondition-
ing voltage threshold (V_MIN), the AAT3673 begins pre-
conditioning the battery cell with charge current which is
10% of the fast charge current.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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201881B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012