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Alarm Broadcasts to Smart Charger and Host
Precharge Qualification
Charge Suspension
bq2084-V143
SLUS732 – SEPTEMBER 2006
If temperature is between the Charge Inhibit Temp Low (DF0x46) and the precharge threshold PC ( ° C), the
bq2084-V143 sets ChargingCurrent() to Precharge Current. The threshold is programmed in the Precharge
Temp DF 0x44. The maximal value of precharge temperature threshold setting is 12.7 ° C.
• Precharge Temp = PC ( ° C) / 0.1
The bq2084-V143 also sets ChargingCurrent() to the precharge rate if Voltage() is less than the value
programmed in Precharge Voltage DF 0x3c-0x3d. Precharge Voltage is programmed in mV.
If any of the bits 8-15 in BatteryStatus() are set, the bq2084-V143 broadcasts an AlarmWarning() message to
the Host address. If any of the bits 12-15 in BatteryStatus() are set, the bq2084-V143 also sends an
AlarmWarning() message to the Smart Charger address. The bq2084-V143 repeats the AlarmWarning()
messages every 10 seconds until the alarm bits are cleared. All broadcasts can be disabled by setting SM (bit 2)
in Pack Configuration (DF 0x28).
The bq2084-V143 sets ChargingCurrent() to the precharge rate as programmed in Precharge Current DF
0x42-0x43 under the following conditions:
• Voltage: The bq2084-V143 requests the precharge charge rate when any cell voltage drops below the
precharge threshold or when the EDV0 threshold is detected. Once requested, a precharge rate remains
until all cell voltages increase above the precharge threshold and the EDV0 condition does not exist. The
precharge threshold is programmed in Precharge Voltage DF 0x3c-0x3d.
• Temperature: The bq2084-V143 requests the precharge rate when Temperature() is between Charge Inhibit
Temp Low (DF0x46) and the precharge threshold programmed in Precharge Temp 0x44. Temperature( )
must be equal to or greater than the precharge threshold + 3 ° C to allow the fast-charge rate.
The bq2084-V143 may temporarily suspend charge if it detects a charging fault. A charging fault includes the
following conditions.
• Overcurrent: An overcurrent condition exists when the bq2084-V143 measures the charge current to be
greater than Charge OC Threshold (DF 0x12a-0x12b) for a time greater than Charge OC Time (DF 0x12c ).
On detecting an overcurrent condition, the bq2084-V143 turns off the Charge FET. If the Nonremovable
Battery bit is not set in Misc Configuration DF 0x2a, then the Discharge FET is turned off also. This condition
is cleared when the pack is removed or if the Nonremovable Battery bit is set in Misc Configuration DF 0x2a
and when a discharge current is detected or when SBS AverageCurrent() is less than the ClearFailCurrent
DF 0x61-0x62 for FaultResetTime DF 0x130.
• Overtemperature: During charging, an overtemperature condition exists when Temperature() is greater than
the Charge Suspend Temp High value programmed in DF 0x6d, 0x6e. On detecting an overtemperature
condition, if enabled by the OT bit in Misc Configuration DF 0x2a, the bq2084-V143 turns off the Charge and
Discharge FETs. The overtemperature condition is cleared when Temperature() is equal to or below Charge
Suspend Temp High Reset (DF 0x6f -0x70) . The condition is also cleared if the pack is removed.
• Undertemperature: During charging, an undertemperature condition exists when Temperature() is less than
the Charge Suspend Temp Low in DF 0x79 or Charge Inhibit Temp Low in DF 0x46. On detecting an
undertemperature condition the bq2084-V143 turns off the Charge FET. The undertemperature condition is
cleared when Temperature() is greater than Charge Suspend Temp Low DF 0x79 . The condition is also
cleared if the pack is removed. The maximal value of Charge Suspend Temp Low setting is 12.7 ° C.
• Charging exceeds Max Charging Time in DF 0x10f-0x110. If charging time reaches DF: Max Charge Time,
the Charge FET is turned off. This condition is cleared when the pack detects discharge current or is
removed. In version bq2084-V143 setting Max Charge Time to 0 will disable this feature. Also in version
bq2084-V143, setting Bit 7 (0x80) of DF:MiscConfig2 will suspend the Charge Timer when the SBS. Current
< DF:Chg Detection threshold.
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