AAT3670ISK-4.2-T1 View Datasheet(PDF) - Analog Technology Inc
Part Name
Description
MFG CO.
'AAT3670ISK-4.2-T1' PDF : 32 Pages View PDF
AAT3670
1.6A Dynamic Battery Charger
and Power Manager
End of Charge Voltage
Regulated Current
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
I = Max CC
Constant Voltage
Charge Phase
(4.2V)
Constant Current Mode
Voltage Threshold
(2.9V)
Trickle Charge
Charge Termination Current
Figure 1: Current vs. Voltage Profile During Charging Phases.
The battery preconditioning trickle charge current
is equal to the fast charge constant current divided
by 10 for the adapter and USB high input modes.
For example, if the programmed fast charge cur-
rent is 500mA, then the preconditioning mode
(trickle charge) current will be 50mA. In the USB
low charging mode, the preconditioning current is
set to the programmed fast charge current divided
by two. Cell preconditioning is a safety precaution
for a deeply discharged battery and also aids in
limiting power dissipation in the charge control
pass transistor when the voltage across the device
is at the greatest potential.
Fast Charge/Constant Current Charging
Battery cell preconditioning continues until the volt-
age measured by the battery sense (BATS) pin
exceeds the preconditioning voltage threshold
(VMIN). At this point, the AAT3670 begins constant-
current charging fast charging phase. The fast
charge constant current (ICC) level is determined by
the charge mode (ADP, USBH or USBL) and is pro-
grammed by the user via the RADPSET and RUSBSET
resistors. The AAT3670 remains in constant current
charge mode until the battery reaches the voltage
regulation point, VBAT_EOC.
Constant Voltage Charging
The charge control system transitions to a regulated
constant voltage charging mode when the battery
voltage reaches output charge regulation threshold
(VBAT_EOC) during constant current fast charge
phase. The regulation voltage level is factory pro-
grammed to 4.2V (±1%). The charge current in the
constant voltage mode drops as the battery cell
under charge reaches its maximum capacity.
End of Charge Cycle Termination and
Recharge Sequence
When the charge current drops to the user pro-
grammed charge termination current at the end of
the constant voltage charging phase, the device
terminates charging and enters the sleep state.
The charger will remain in the sleep state until the
battery voltage decreases to a level below the bat-
tery recharge voltage threshold (VRCH). The charge
termination current is programmed via the RTERM
resistor.
When the input supply is disconnected, the charg-
er also automatically enters power-saving sleep
mode. Only consuming an ultra-low 1µA in sleep
mode, the AAT3670 minimizes battery drain when
not charging. This feature is particularly useful in
applications where the input supply level may fall
below the usable range of the charge reduction
control or under-voltage lockout level. In such
cases where the AAT3670 input voltage drops, the
device will enter the sleep mode and automatically
resume charging once the input supply has recov-
ered from its fault condition.
20
3670.2007.02.1.1
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