AAT3673 Datasheet, PDF (20/28 Pages) Skyworks Solutions Inc. – 1.6A Dynamic Battery Charger and Power Manager

DATA SHEET
AAT3673
1.6A Dynamic Battery Charger and Power Manager
Applications Information
Adapter or USB Port Power Source
In the adapter mode, constant current charge levels up
to 1.6A may be programmed by the user. The ADP input
will operate over a range from 4.0V to 6.5V.
The constant fast charge current for the adapter input
mode is set by the R_ADP resistor connected between the
ADPSET pin and ground. The battery preconditioning or
trickle charge current is fixed at 10% of the programmed
fast charge constant current level. Refer to Table 4 for
recommended R_ADP values for a desired constant current
charge level. Please refer to the Battery Charge Status
Indication discussion on page 21 of this datasheet for
further details.
Charge Reduction
Under normal operation, the AAT3673 should be operat-
ed from an adapter power source with a sufficient capac-
ity to supply the desired constant charge current plus
any additional load which may be placed on the source
by the operating system. In the event that the power
source to the ADP pin is unable to provide the pro-
grammed fast charge constant current, or if the system
under charge must also share supply current with other
functions, the AAT3673 will automatically reduce the ADP
fast charge current level to maintain the integrity of the
source supply, power the operating system, and charge
the battery cell with the remaining available current.
The ADP charge reduction system becomes active when
the voltage on the ADP input falls below the ADP charge
reduction threshold (V_{CHR_TH}), which is preset to 4.5V.
Should the input supply drop below the V_{CHR_TH} threshold,
the charge reduction system will reduce the fast charge
current level in a linear fashion until the voltage sensed
on the ADP input recovers to the charge reduction thresh-
old voltage. The ADP charge reduction threshold (V_{CHR_TH})
may be externally set to a value other than 4.5V by plac-
ing a resistor divider network between the BYP pin and
ground with the center connected to the CHRADP pin. The
ADP charge reduction feature may be disabled by shorting
the CHRADP pin directly to the BYP pin.
The following equation may be used to approximate the
ADP charge reduction threshold above or below 4.5V:
V_{CHR_TH}
=
2.0V
(R4/[R4 +
R3])
where R4 and R3 « 500k.
BYP
BYP
R3
CHRADP
R4
1M
V_{CH_REG}= 2.0
800k
Figure 3: Internal Equivalent Circuit
for the CHRADP Pin.
Adapter Input Charge
Inhibit and Resume
The AAT3673 has an under-voltage lockout (UVLO) and
power on reset feature to protect the charger IC in the
event the voltage on the BYP pin drops below the UVLO
threshold. Under a UVLO condition, the charger will sus-
pend the charging process. When power is applied to the
adapter pin again or the UVLO condition recovers, the
system charge control will asses the state of charge on
the battery cell and will automatically resume charging in
the appropriate mode for the condition of the battery.
Programming Fast Charge Current
The constant current charge level is user programmable
with a set resistor connected between the ADPSET pin
and ground. The accuracy of the constant charge cur-
rent, as well as the preconditioning trickle charge cur-
rent, is dominated by the tolerance of the set resistor
used. For this reason, a 1% tolerance metal film resistor
is recommended for the set resistor function. The con-
stant charge current levels from 100mA to 1.6A may be
set by selecting the appropriate value from Table 4.
Charge current setting formula:
I_{CH_CC_ADP} (typ) =
V_ADP
R_ADP
· KI_{I_CC_ADP}
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
20
201881B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012