AAT3689 데이터 시트보기 (PDF) - Advanced Analogic Technologies

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AAT3689

0.5A/1.0A USB Port/Adapter Lithium-Ion/Polymer Battery Charger

Advanced Analogic Technologies 

AAT3689

0.5A/1.0A USB Port/Adapter

Lithium-Ion/Polymer Battery Charger

Charge Complete Voltage

Regulated Current

Preconditioning

Trickle Charge

Phase

Constant Current

Charge Phase

I = Max CC

Constant Voltage

Charge Phase

Constant Current Mode

Voltage Threshold

Trickle Charge and I = CC / 10

Termination Threshold

Figure 1: Current vs. Voltage Profile During Charging Phases.

Battery Preconditioning

Before the start of charging, the AAT3689 checks

several conditions in order to assure a safe charging

environment. The input supply must be above the

minimum operating voltage, or under-voltage lock-

out threshold (VUVLO), 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 AAT3689 checks

the state of the battery. If the cell voltage is below the

Preconditioning Voltage Threshold (VMIN), the

AAT3689 begins preconditioning the cell.

The battery preconditioning trickle charge current is

equal to the fast charge constant current divided by

10. For example, if the programmed fast charge cur-

rent is 500mA, then the preconditioning mode (trick-

le charge) current will be 50mA. Cell preconditioning

is a safety precaution for a deeply discharged bat-

tery and also aids in limiting power dissipation in the

pass transistor when the voltage across the device

is at the greatest potential.

Fast Charge / Constant Current Charging

The cell preconditioning continues until the voltage

on the BAT pin exceeds the Preconditioning Voltage

Threshold (VMIN). At this point, the AAT3689 begins

the constant-current fast charging phase. The fast

charge Constant Current (ICC) amplitude is deter-

mined by the charge mode, ADP or USB, and is pro-

grammed by the user via the RSETADP and RSETUSB

resistors. The AAT3689 remains in constant current

charge mode until the battery reaches the voltage

regulation point, VBAT_EOC.

Constant Voltage Charging

The system transitions to a constant voltage charg-

ing mode when the battery voltage reaches output

charge regulation threshold (VBAT_EOC) during the

constant current fast charge phase. The regulation

voltage level is factory programmed 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 7.5% of the pro-

grammed fast charge current level in the constant

voltage mode, the device terminates charging and

goes into a standby state. The charger will remain

in a standby state until the battery voltage decreas-

es to a level below the battery recharge voltage

threshold (VRCH).

When the input supply is disconnected or drops

below UVLO or EN = 0, the charger will automatical-

ly enter power-saving sleep mode. Consuming an

ultra-low 0.3μA in sleep mode, the AAT3689 mini-

mizes battery drain when it is not charging. This fea-

ture is particularly useful in applications where the

input supply level may fall below the battery charge or

under-voltage lockout level. In such cases where the

AAT3689 input voltage drops, the device will enter the

sleep mode and automatically resume charging once

the input supply has recovered from its fault condition.

3689.2006.11.1.0

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