ACT3780

Rev 8, 09-Jul-13

- 13 -

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Copyright © 2013 Active-Semi, Inc.

Active-Semi Proprietary―For Authorized Recipients and Customers

ActivePath

Charger State-Machine

PRECONDITION State

A

new

charging

cycle

begins

with

the

PRECONDITION state, and operation continues in

Threshold Voltage of 2.85V (typ). When operating

in PRECONDITION state, the cell is charged at a

reduced current, 10% of the programmed maximum

reaches the Precondition Threshold Voltage the

state machine jumps to the FAST-CHARGE state. If

Voltage before the Precondition Timeout period

detected and the state machine jumps to the

TIMEOUT- FAULT State. For the Precondition

Timeout period, see the Charging Safety Timers

section

for more information.

FAST-CHARGE State

In FAST-CHARGE state, the ACT3780 charges at

Limits

and Charge Current Programming section for

more information). During a normal charge cycle

which point the ACT3780 charges in TOP-OFF

CHARGE state before the Normal Timeout period

the END-OF-CHARGE state and will re-initiate a

new charge cycle after 2-4ms “relax”.

TOP-OFF State

In the TOP-OFF state, the cell is charged in

constant-voltage

(CV)

mode.

Charge

current

decreases as charging continues. During a normal

charging cycle charging proceeds until the charge

current decreases below the END-OF-CHARGE

(EOC) threshold, defined as 10% of ISET (ACIN =

1) or 4% of ISET (ACIN = 0) . When this happens,

the state-machine terminates the charge cycle and

jumps to the 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 termination voltage.

END-OF-CHARGE State

In

the

END-OF-CHARGE

(EOC)

state,

the

ACT3780 presents a high-impedance to the battery,

allowing the cell to “relax” and minimizes battery

leakage current. The ACT3780 continues to monitor

the cell voltage, however, so that it can re-initiate

the charge termination voltage.

SUSPEND State

The ACT3780 features an user-selectable suspend

charge mode, which disables the charger but keeps

other circuiting functional. The charger can be put

into suspend mode by driving EN to logic low. Upon

exiting the SUSPEND State, the charge timer is

reset

and

the

state

machine

jumps

to

PRECONDITION state.

Figure 5:

Typical Li+ Charge Profile and ACT3780 Charge States

A: PRECONDITION State

B: FAST-CHARGE State

C: TOP-OFF State

D: END-OF-CHARGE State