AAT3603 datasheet(22/35 Pages) ANALOGICTECH

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AAT3603178

Total Power Solution for Portable Applications

PRODUCT DATASHEET

3603.2008.06.1.0

www .analogictech.com

Battery Charger

Figure 3 illustrates the entire battery charging profile

which consists of three phases.

1. Preconditioning Current Mode (Trickle) Charge

2. Constant Current Mode Charge

3. Constant Voltage Mode Charge

Preconditioning Trickle Charge

Battery charging commences only after the AAT3603

battery charger checks several conditions in order to

maintain a safe charging environment. The system

operation flow chart for the battery charger operation is

shown in Figure 4. The input supply must be above the

minimum operating voltage (UVLO) and the enable pin

(ENBAT) must be low (it is internally pulled down). When

the battery is connected to the BAT pin, the battery

charger checks the condition of the battery and deter-

mines which charging mode to apply.

Preconditioning Current Mode

Charge Current

If the battery voltage is below the preconditioning volt-

age threshold VMIN, then the battery charger initiates

precondition trickle charge mode and charges the bat-

tery at 12% of the programmed constant-current mag-

nitude. For example, if the programmed current is

500mA, then the trickle charge current will be 60mA.

Trickle charge is a safety precaution for a deeply dis-

charged cell. It also reduces the power dissipation in the

internal series pass MOSFET when the input-output volt-

age differential is at its highest.

Constant Current Mode Charge Current

Trickle charge continues until the battery voltage reach-

es VMIN. At this point the battery charger begins con-

stant-current charging. The current level default for this

mode is programmed using a resistor from the ISET pin

to ground. Once that resistor has been selected for the

default charge current, then the current can be adjusted

through I2C from a range of 40% to 180% of the pro-

grammed default charge current. Programmed current

can be set at a minimum of 100mA and up to a maxi-

mum of 1A. When the ADPP signal goes high, the default

I2C setting of 100% is reset.

Constant Voltage Mode Charge

Constant current charging will continue until the battery

voltage reaches the Output Charge Voltage Regulation

point VBAT_REG. When the battery voltage reaches the regu-

lation voltage (VBAT_REG), the battery charger will transition

to constant-voltage mode. VBAT_REG is factory programmed

to 4.2V (nominal). Charging in constant-voltage mode will

continue until the charge current has reduced to the end

of charge termination current programmed using the I2C

interface (5%, 10%, 15%, or 20%).

Constant Current

Charge Phase

Constant Voltage

Charge Phase

Preconditioning

Trickle Charge

Phase

I (mA)

V (V)

Preconditioning Threshold

Voltage (VMiN)

Charge Termination

Threshold Current

(ICH_TERM)

T (s)

Battery End of Charge

Voltage Regulation (VBAT_REG)

FAST-CHARGE to

TOP-OFF Charge

Threshold

Trickle Charge

Timeout

(TK)

Constant-Current Mode

Charge Current (ICH_CC)

Preconditioning Charge

Current (ICH_PRE)

Charge Current

Charge Voltage

Constant Current Timeout

(TC)

Constant Voltage Timeout

(TV)

Figure 3: Current vs. Voltage and Charger Time Profile.

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