ACT5880
Rev 2, 03-Sep-13
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.
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.
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.
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.
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.
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.
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
Charge State Output
The ACT5880 has 2 configurable time-out timers to
count the elapsed time during precondition and the
overall elapsed time during charge.
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.
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.
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.
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.
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
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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