ACT5830 datasheet(39/41 Pages) ACTIVE-SEMI

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SINGLE-CELL Li+ BATTERY CHARGER (CHGR)

ACT5830

Rev PrB, 05-Mar-08

Innovative Power

- 39 -

www.active-semi.com

ActivePMU

TM is a trademark of Active-Semi.

2CTM is a trademark of Philips Electronics.

FUNCTIONAL DESCRIPTIONS CONT’D

Charge Safety Timer

While monitoring the charge cycle, the ACT5830

utilizes a charge safety timer to help identify dam-

aged cells and to ensure that the cell is charged

safely. Three timeout options of 60 minutes, 30 min-

utes, and 45minutes are available, as programmed

by the CHGR/TIMOSET register, and a timer-

disable option is also available for systems that do

not require the ACT5830 to control charge timeouts.

The bit assignments for each timeout period are set

as follows:

CHGR State-Machine

PRECONDITION State

A new charging cycle begins with the PRECONDI-

TION state. In this state, the cell is charged at a

reduced current of 10% of ISET, the programmed

fast charge current. During a normal charge cycle,

charging continues at this rate until VBAT reaches

the Precondition Threshold Voltage of 2.9V (typ), at

which point the charging state machine jumps to its

FAST-CHARGE state. If VBAT does not reach the

Precondition Threshold Voltage before the charge

timeout period expires, then a damaged cell is de-

tected and the state machine jumps to the TIME-

OUT-FAULT State.

FAST-CHARGE State

In FAST-CHARGE mode, the charger operates in

constant-current (CC) mode and charges the cell at

the current programmed by CHGR/ISET. During a

normal charge cycle fast-charge continues until

VBAT reaches the termination voltage programmed

by VSET, at which point the state machine jumps to

the TOPOFF state.

TOP-OFF State

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

stant-voltage (CV) mode. With the charge current

limited by the internal chemistry of the cell, de-

creases as charging continues. During a normal

charging cycle charging proceeds until the charge

current decreases beyond the End-Of-Charge

(EOC) threshold, defined as 10% of ISET. When

this happens, the state machine terminates the

charge cycle and jumps to the SLEEP state.

SLEEP State

In SLEEP mode the ACT5830 presents a high-

impedance to the battery, allowing the cell to “relax”

and minimizing battery leakage current. The

ACT5830 continues to monitor the cell voltage,

however, so that it can re-initiate charging cycles as

necessary to ensure that the cell remains fully

charged. Under normal operation, the state ma-

chine initiates a new charging cycle by jumping to

the FAST-CHARGE state when VBAT drops below

the Charge Termination Threshold (programmed by

VSET) by more than the Charge Restart Threshold

of 200mV (typ).

SUSPEND State

The ACT5830 features a user-selectable suspend-

charge mode (SUSCHG), which disables the

charger but keeps other circuitry functional. Charg-

ing continues in the SUSPEND state until

CHGR/SUSPEND is cleared, at which point the

charge timer is reset and the state machine jumps

to the PRECHARGE state.

Suspend charge by setting CHGR/SUSCHG = [1].

Permit charging by clearing CHGR/SUSCHG to [0].

TIMEOUT-FAULT State

In order to prevent continued operation with a dam-

aged ce ll, there is no direct path to resume charg-

ing once a Timeout Fault occurs. In order to resume

charging, the state machine must jump to the SUS-

PEND state as a result of any of the following

events:

microprocessor sets CHGR/SUSCHG to [1],

microprocessor pulls nENCHG high,

the input supply is removed or the input suppl volt-

age drops below the UVLO threshold (4V), or

the battery is removed. Once any of these events

TIMOSET

[1:0 ]

PRECONDITION

TIMEOUT

TOTAL CHARGING

TIMEOUT

60 mins (default)

3.0 hours (default)

TIMER DISABLED

30 mins

1.5 hours

45 mins

2.2 hours

Table 12:

TIMOSET[ ] Timeout Period Options

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