bq20z80-V101
www.ti.com
SLUS625D–SEPTEMBER 2004–REVISED OCTOBER 2005
1st LEVEL PROTECTION FEATURES
The bq20z80 supports a wide range of battery and system protection features that are easily configured or
disabled via the integrated data flash.
Cell Overvoltage
The bq20z80 can disable charging by turning off the charge FET if any cell voltage is ≥ DF:COV Threshold for
a ≥ DF:COV Time. This feature is disabled if DF:COV Time = 0.
During the time between when an excessive voltage is first detected and the expiration of DF:COV Time,
SBS.SafetyAlert( ) [COV] is set. If, during this period, the voltage falls below the DF:COV Threshold, this flag is
cleared.
If DF:COV Time expires, the charge FET is turned off. The ZVCHG FET is also turned off if the DF:Operation
Cfg A [ZVCHG1, ZVCHG0] bits are set appropriately. Also, when DF:COV Time expires, SBS.ChargingCurrent( )
and SBS.ChargingVoltage(
) are cleared, SBS.BatteryStatus( ) Terminate_Charge_Alarm is set, and
SBS.SafetyStatus( ) [COV] is set.
For the bq20z80 to fully recover from a cell overvoltage condition, all SBS.CellVoltagex( ) values must be ≤ the
DF:COV Recovery threshold. When this occurs, the charge FET is allowed to be turned on only if other safety
and configuration states permit. On recovery from an overvoltage condition, SBS.BatteryStatus(
)
Terminate_Charge_Alarm is reset, SBS.ChargingCurrent( ) and SBS.ChargingVoltage( ) are set to the
appropriate value per the charging algorithm, and SBS.SafetyStatus( ) [COV] is reset.
However, when the bq20z80 has SBS.SafetyStatus( ) [COV] set, the charge FET is turned on again while
SBS.Current( ) is reported to be ≤ (-) DF:Dsg Current Threshold. No other flags change state until full recovery
is reached. This prevents overheating the charge-FET body diode during discharge from an overvoltage
condition.
SIZE
(BYTES)
DEFAULT
VALUE
NAME
CLASS / SUBCLASS
FORMAT
VALID RANGE
UNITS
COV Threshold
COV Recovery
COV Time
3700 to 5000
0 to 4400
0 to 60
2
2
1
4300
3900
2
mV
s
1st Level Safety / Voltage (0)
Integer
Cell Overvoltage Threshold Compensation
If the bq20z80 detects charging (SBS.BatteryStatus( ) [DSG] = 0) the actual threshold for cell-overvoltage
detection may be reduced, based on the reported SBS.Temperature( ).
If SBS.Temperature( ) is > DF:Over Temp Chg–DF:COV Temp Hys, the actual cell-overvoltage threshold used is
DF:COV Threshold–DF:COV Delta. However, if DF:COV Delta = 0 then the compensation of the cell-overvoltage
threshold is disabled.
SIZE
(BYTES)
DEFAULT
VALUE
NAME
DESCRIPTION
FORMAT
VALID RANGE
UNITS
Overtemp Chg
COV Temp Hys
COV Delta
1st Level Safety / Temperature (2)
0 to 1200
0 to 250
0 to 200
2
1
1
550
100
20
0.1°C
Integer
1st Level Safety / Voltage (0)
mV
Pack Overvoltage
The bq20z80 can disable charging by turning off the charge FET if SBS.Voltage( ) is ≥ DF:POV Threshold for a
period ≥ DF:POV Time. However, if DF:POV Time = 0, this feature is disabled.
During the period between when an excessive voltage is detected and the expiration of DF:POV Time, the
SBS.SafetyAlert( ) [POV] bit is set. If during this period, the voltage falls below the DF:POV Threshold, this flag is
cleared.
If DF:POV Time expires, the charge FET is turned off. The ZVCHG FET is also turned off if the DF:Operation Cfg
A [ZVCHG1, ZVCHG0] bits are set appropriately. Also, when DF:POV Time expires, SBS.ChargingCurrent( ) and
SBS.ChargingVoltage(
)
are set to 0, SBS.BatteryStatus(
)
Terminate_Charge_Alarm is set, and
SBS.SafetyStatus( ) [POV] is set.
12
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