ACT5880 datasheet(81/87 Pages) ACTIVE-SEMI

81 / 87 page

ACT5880

Rev 2, 03-Sep-13

- 81 -

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Sleep State

In the Sleep State, the charger represents as high-

impedance to the cell and is with only the leakage

current. The VVBAT is actively monitored by the state

machine all the time. When VVBAT drop of typical

200mV being seen, the state machine begins a new

charge cycle.

Time-Fault State

If the function is enabled, the pre-condition charge

time are counted. When the pre-condition time-out

happens, the state machine jumps into Time-Fault

State. The Time-Fault State could only exit into End

-of-Charge State when VVBAT ever goes to less than

the pre-condition threshold voltage or BATID ever

reads invalid, which is presumably a battery

replacement. Charge input power recycle does not

reset the Time-Fault State.

Temp-Fault

When this function is enabled, the battery

temperature is monitored whenever a suitable

power applies on CHGIN. When battery is too cold

or too hot, the state machine jumps into Sleep State

for the temp-fault. In this state, the charger

represents as high impedance to the cell, the

charger circuitry remains functional waiting for the

battery thermal condition changes.

Charge State Output

nSTAT Output

The nSTAT is an open-drain output for simple

charge status output. It has an internal 8mA current

limit and is capable to drive an LED for visual

indication without the need of current limit resistor

or other external circuitry doing the current limit.

The nSTAT sinks current in precondition state, fast-

charge state and top-off state. It turns into high

impedance in sleep state and time-fault state.

CHG_STAT0[ ] and CHG_STAT1[ ] registers

indicate 4 different charge states, which are the Off

state (the force suspend state, the Time-Fault state,

the Temp-Fault state or the LDO mode), the Sleep

state, the Fast-Charge state or Top-Off state and

the Pre-condition state. Those bits can be read

through the I2C interface.

Charge Oriented Interrupts

When the configuration enables to assert interrupt,

the state change in the charger asserts interrupt to

call service from the host system. The interrupt

configuration is flexible to select which state and

what kind of state change for interrupt assertion.

Each interrupt has 2 bits to allow interrupt, one bit

of the latest status of the respective state by the

time of reading and a bit to specify which kind of

change for asserting interrupt.

It is factory-option to have the Temp-Fault state or

the BATID state to use the same set of 3 bits for

configuring and flag. When Temp-Fault option is

selected, which enables the battery thermal

condition, the BATID state is not cared for

interrupting. When the BATID is selected, the

battery thermal condition is disabled, then the

BATID state uses the set of the 3 bits. Refer to the

INTERRUPT DESCRIPTION

table for more details.

Reading the CHGSTAT byte to clear the asserted

interrupt.

Safe Charge and Operation

It is important to a system running on high energy

battery that it only charges and operates on a

qualified cell, and the behavior is within an

predictable safe situation. The ACT5880 has

following features available for system design

selection.

Resistive Battery Identification

The ACT5880 has 3 auxiliary ADC inputs. The

auxiliary input could be used to read voltage when

forcing a current through the designed identification

resistor in the battery pack.

Charge Safety Timer

The ACT5880 has 2 configurable time-out timers to

count the elapsed time during precondition and the

overall elapsed time during charge.

When this function is enabled, if the cell could not

be charged to correct state in predicted maximum

time, the charger stops charging and restarts only

when the battery is replaced presumably.

Both time-out periods are programmable, refer to

the REGISTER MAP AND DESCRIPTIONS section

for more details.

Battery Thermal Condition

The battery thermal condition is a feature option

against ordering. If this feature is optioned, the

battery temperature is monitored and the charging

is allowed only when the battery voltage is within a

specified temperature window for the safe of battery

and the equipment normal operation.

Precise window comparators are used for battery

thermal condition, see the Figure 18 for circuit

diagram. The window thresholds are trimmed to 2

precise ratios, and the external sense string is

forced with the same force voltage used for

comparators, the VCHGIN. The 2 resistors, RA and

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