AAT3670 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'AAT3670' PDF : 32 Pages View PDF
BatteryManagerTM
PRODUCT DATASHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Applications Information
AC Adapter/USB System Power Charging
Adapter Input Mode
In the adapter mode, constant current charge levels up
to 1.6A may be programmed by the user. The AAT3670
system control will always select the adapter input over
the USB supply input when ever voltage is present on
the ADP pin. The ADP input will operate over a range
from 4.35V to 5.5V.
The constant fast charge current for the adapter input
mode is set by the RADPSET 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 2 for
recommended RADPSET values for a desired constant cur-
rent charge level. Battery charging states will be indi-
cated via the STAT1 and STAT2 display LEDs. Please
refer to the Battery Charge Status Indication discussion
for further details on data reporting.
ADP Charge Reduction
Under normal operation, the AAT3670 should be operated
from an adapter power source with a sufficient capacity
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 programmed fast
charge constant current, or if the system under charge
must also share supply current with other functions, the
AAT3670 will automatically reduce the ADP fast charge
current level to maintain the integrity of the source sup-
ply, 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 (VCHRADP), which is preset to 4.6V.
Should the input supply drop below the VCHRADP 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 a point above the charge
reduction threshold voltage. The ADP charge reduction
threshold (VCHRADP) may be externally set to a value other
than 4.6V by placing a resistor divider network between
the ADP 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 ADP
input pin.
The following equation may be used to approximate the
ADP charge reduction threshold above or below 4.5V:
Eq.
1:
VADPCHR
=
2.0V
(R12/[R12 +
R11])
where R11 and R12 < 500kΩ.
VADP
ADP
R11
CHRADP
R12
850k
VCHR = 2.0V
650k
Figure 3: Internal Equivalent Circuit for the
CHRADP Pin.
Adapter Input Charge Inhibit and Resume
The AAT3670 has an under-voltage lockout (UVLO) and
power on reset feature to protect the charger IC in the
event the input supply to the adapter pin drops below
the UVLO threshold. Under a UVLO condition, the char-
ger will suspend the charging process. When power is
re-applied to the adapter pin 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 condi-
tion of the battery.
USB Input Mode
The AAT3670 provides an input for intelligent USB charg-
ing. When no voltage is present on the adapter input pin,
the charge controller will automatically switch to accept-
ing power from the USB input. The USB charge mode
provides two programmable fast charge levels, USB high
(USBH) and USB low (USBL). The USBH mode can be set
as high as 900mA; however for most applications utiliz-
ing a USB port as the source supply, 500mA is the typical
20
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