ACT8600 datasheet(46/51 Pages) ACTIVE-SEMI

46 / 51 page

ACT8600

Rev 3, 15-Nov-12

Innovative Power

ActivePMU

TM and ActivePathTM are trademarks of Active-Semi.

2CTM is a trademark of NXP.

- 46 -

www.active-semi.com

Charge-Control State Machine

PRECONDITION State

new

charging

cycle

begins

with

the

PRECONDITION state, and operation continues in

this state until VBAT exceeds the Precondition

Threshold

Voltage.

When

operating

PRECONDITION state, the cell is charged at 10%

of the programmed maximum fast-charge constant

current, ICHG.

Once VBAT reaches the Precondition Threshold

Voltage, the state machine jumps to the FAST-

CHARGE state. If VBAT does not reach the

Precondition

Threshold

Voltage

before

the

Precondition Timeout period expires, then the state

machine jumps to the TIMEOUT-FAULT state in

order to prevent charging a damaged cell. See the

Charge Safety Timers

section for more information.

FAST-CHARGE State

In the FAST-CHARGE state, the charger operates

in constant-current (CC) mode and regulates the

charge current to the current set by RISET . Charging

continues in CC mode until VBAT reaches the charge

termination voltage (VTERM), at which point the state-

machine jumps to the TOP-OFF state. If VBAT does

not reach VTERM before the total time out period

expires then the state-machine will jump to the

“EOC” state and will re-initiate a new charge cycle

after 32ms “relax”. See the Current Limits and

Charge Current Programming

sections for more

information about setting the maximum charge

current.

TOP-OFF State

In the TOP-OFF state, the cell charges in constant-

voltage (CV) mode. In CV mode operation, the

charger regulates its output voltage to the 4.20V

charge termination voltage, and the charge current

is naturally reduced as the cell approaches full

charge. Charging continues until the charge current

drops to END-OF-CHARGE current threshold, at

which point the state machine jumps to the END-

OF-CHARGE (EOC) state.

If the state-machine does not jump out of the TOP-

OFF state before the Total-Charge Timeout period

expires, the state machine jumps to the EOC state

and will re-initiate a new charge cycle if VBAT falls

below termination voltage 205mV (typ). For more

information about the charge safety timers, see the

Charging Safety Times

section.

END-OF-CHARGE (EOC) State

In the END-OF-CHARGE (EOC) state, the charger

presents

high-impedance

the

battery,

minimizing battery current drain and allowing the

cell to “relax”. The charger continues to monitor the

cell voltage, and re-initiates a charging sequence if

the cell voltage drops to 205mV (typ) below the

charge termination voltage.

SUSPEND State

The state-machine jumps to the SUSPEND state

any time the battery is removed, and any time the

input voltage falls below either the UVLO threshold

or exceeds the OVP threshold. Once none of these

conditions are present, a new charge cycle initiates.

A charging cycle may also be suspended manually

by setting the SUSPEND[ ] bit. In this case, initiate

a new charging sequence by clearing SUSPEND[ ]

to 0.

State Machine Status

The charger features the ability to generate

interrupts

when

the

charger

state

machine

transitions. Set CHGEOCIN[ ] bit to 1 and

CHGSTAT[ ] bit to 1 to generate an interruption

when the charger state machine goes into the END-

OF-CHARGE (EOC) state. Set CHGEOCOUT[ ] bit

to 1 and CHGSTAT[ ] bit to 1 to generate an

interruption when the charger state machine exists

the EOC state.

The status of the charge state machine may be

read at any time by reading the CHGDAT[ ] bit,

where a value of 1 indicates State Machine is in

EOC state, and value is 0 when State Machine is

in other states. Reading the CHGSTAT[-] bit

indicates when a state machine transition has

generated an interrupt; this bit will normally return a

value of 0, but will return value of 1 when a state

transition occurs then automatically clear to 0 upon

reading.

For additional information about the charge cycle,

CSTATE[0:1] may be read at any time via I2C to

determine the current charging state.

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