PT8A2707 Datasheet, PDF (8/26 Pages) Pericom Semiconductor Corporation – Charger Controller with Fuel-Guage & LCD/LED Display

PT8A2707-12/17-19
Charger Controller
with Fuel-Guage & LCD/LED Display
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a) If the motor is turned on during the pre-charge state, obviously there is no charging current to battery. The PT8A2707-
12/2717-19 will return to discharging mode while fuel-gauge is continuing to count the discharge amount. The
discharging is stopped at the same criteria described in the Discharging Mechanism section.
b) If the motor is turned on during the fast-charge state, the fast-charge safety timer is held. If the motor is turned on less
than 5% of the battery maximum capacity, fast-charge resumes with fast-charge timer continue to count (but start-up
timer starts from beginning). However, when the motor is accumulatively turned on over 5% of the battery maximum
capacity while cord is still connected, the fast-charge timer is cleared and the battery pack will be recharged from pre-
charge state again once motor is off.
c) If the motor is turned on during the trickle-charge state, if the motor is turned on to accumulatively consume less than
5% (not necessarily in single operation) of the battery maximum capacity, the PT8A2707-12/2717-19 resumes trickle-
charge state. However, when the motor is turned on over 5% of the battery maximum capacity during the trickle-charge
state, the battery pack will be recharged from pre-charge state again after motor is off.
Besides, at any time when the battery pack voltage is lower than the No-Power value or discharging current is higher than the
preset limit levels for 3sec, the motor will be stopped and the devices return to charging status.
2) The motor is turned on but draws less current than the AC/DC adapter can supply: In all cases, when the battery is not
discharged, the PT8A2707-12/2717-19 regulates a charging current of 1/10 of the fast-charge current to battery pack. In this
case, the battery pack is under slow charging. Similarly, there are three more situations to observe:
a) If the motor is turned on during the pre-charge state, once motor is turned off, the PT8A2707-12/2717-19 will resume
back to the pre-charge state.
b) If the motor is turned on during the fast-charge state, the fast-charge timer is held until motor is turned off to resume
fast-charging.
c) If the motor is turned on during the trikle-charge state, once motor is turned off, the PT8A2707-12/2717-19 will resume
back to the maintenance state.
In any charging states, if the battery temperature is measured higher than 55C, the motor is stopped and the 0.1C charging current
is cut off. The LED/LCD still displays as in “Charging Mode”. The motor will draw current from battery pack until the battery
temperature is below 55C to resume 0.1C charging current. However, no matter whether it is in fast-charging or trickle-charging
modes, when the motor is turned on to consume over 5% (accumulatively, not necessarily in single operation) of the battery
maximum capacity during battery is over-temperature, the battery pack will be recharged from pre-charge state again after motor
is off.
5. Fuel-Gauge Counter
1) Charge Counting: Charge activity is detected based on positive voltage difference (VFUEL) between the pins ISENFG and
ISENCOM. When voltage of ISENFG is higher than the voltage of ISENCOM, the PT8A2707-12/2717-19 increments its
fuel-gauge counter at a rate proportional to VFUEL. VFUEL is sampled and converted into digital data through high-
precision A/D converter. When the fuel-gauge counter accumulates up to 99% level but none of the full-charge criteria (-V,
dT/dt, safety timer, maximum battery voltage) is detected, the fuel-gauge will wait at 99% level. Right after the battery is
fully-charged, the PT8A2707-12/2717-19 displays full-charge and learns the capacity of the battery pack such that the display
will be more and more accurate in both charging and discharging cycles later.
2) Discharge Counting: Discharge activity is detected based on a negative voltage difference (VFUEL) between the pins
ISENFG and ISENCOM. When voltage of ISENFG is lower than the voltage of ISENCOM, the PT8A2707-12/2717-19
decrements its fuel-gauge counter at a rate proportional to VFUEL. VFUEL is sampled and converted into digital data
through high-precision A/D converter. In case the fuel-gauge counter rolls to zero count while the battery voltage is still
higher than the preset No-Power level, the Battery-Low LED is still flashing while user can still use motor. Motor will be
stopped when battery voltage is below the No-Power level. The maximum fuel value is not updated, but will be updated when
necessary for next time the battery is fully charged. The fuel value will be adjusted to 10% if the battery voltage gradually
falls below Battery-Low threshold.
6. Idle Mode
1) Standby: When cord is not connected and motor is off, the PT8A2707-12/2717-19 turn to idle state to save power. Some
internal circuits are shut-down to keep the standby power at about 20A.
2) Background Offset Cancellation: when the PT8A2707-12/2717-19 is waked up by user, an offset cancellation is performed
for the internal precise A/D converter before entering cord or motor modes. It normally takes 0.2~0.3s. The PT8A2707-
12/2717-19 returns to idle state after use.
12-07-0005
PT0268-1 07/05/12
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