ACT8941A datasheet(38/42 Pages) ACTIVE-SEMI

38 / 42 page

ACT8941A

Rev 0, 12-Mar-13

- 38 -

www.active-semi.com

ActivePMU

TM and ActivePathTM are trademarks of Active-Semi.

I2CTM is a trademark of NXP.

Innovative PowerTM

Active-Semi Proprietary―For Authorized Recipients and Customers

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 Time-out period expires, then the state

machine jumps to the TIME-OUT-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 Time-out period

expires, then 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 either falls below the CHGIN 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 Interrupts

The charger features the ability to generate

interrupts

when

the

charger

state

machine

transitions, based upon the status of the CHG_ bits.

Set CHGEOCIN[ ] bit to 1 and CHGSTAT[ ] bit to 1

to generate an interrupt 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 interrupt when the charger

state machine exits the EOC state.

CHGDAT[ ] indicates the status of the charger state

machine. A value of 1 indicates that the charger

state machine is

in END-OF-CHARGE state, a

value of 0 indicates the charger state machine is in

other states.

When an interrupt is generated by the charger state

machine, reading the CHGSTAT[ ] returns a value

of 1. CHGSTAT[ ] is automatically cleared to 0 upon

reading. When no interrupt is generated by the

charger state machine, reading the CHGSTAT[ ]

returns a value of 0.

For additional information about the charge cycle,

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

determine the current charging state.

Table 10:

Charging Status Indication

CSTATE[1] CSTATE[0]

STATE MACHINE STATUS

PRECONDITION State

FAST-CHARGE/

TOP-OFF State

END-OF-CHARGE State

SUSPEND/DISABLED/

FAULT State

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