bq20z80-V101
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SLUS625D–SEPTEMBER 2004–REVISED OCTOBER 2005
For the bq20z80 to fully recover from a pack overvoltage condition, SBS.Voltage( ) must be ≤ DF:POV 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 a pack 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( ) [POV] is reset.
However, when the SBS.SafetyStatus( ) [POV] bit 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 the 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
POV Threshold
POV Recovery
POV Time
0 to 18000
0 to 17000
0 to 60
2
2
1
17500
16000
2
mV
s
1st Level Safety / Voltage (0)
Integer
Cell Undervoltage
The bq20z80 can disable discharging by turning off the discharge FET if any SBS.CellVoltagex( ) is ≤ DF:CUV
Threshold for a period ≥ DF:CUV Time. This feature is disabled if DF:CUV Time = 0.
During the period between the time when a low voltage is first detected and the expiration of DF:CUV Time, the
SBS.SafetyAlert( ) [CUV] bit is set. If, during this period, the voltage rises above DF:CUV Threshold, this flag is
cleared.
If DF:CUV Time expires, the discharge FET is turned off and the ZVCHG FET is turned on if DF:Operation Cfg A
[ZVCGH1, ZVCHG0] are set appropriately. Also, when DF:CUV Time expires, SBS.BatteryStatus( ) [TDA, FD]
are set, SBS.ChargingCurrent( ) is set to DF:Pre-Charge Current, SBS.OperationStatus( ) [XDSG] is set and
SBS.SafetyStatus( [CUV] is set.
For the bq20z80 to fully recover from a cell undervoltage condition, all SBS.CellVoltagex( ) values should
be ≥ DF:CUV Recovery threshold. When this occurs, the discharge FET is allowed to be turned on only if other
safety and configuration states permit. On recovery from an undervoltage condition, SBS.BatteryStatus( ) [TDA]
is reset, SBS.ChargingCurrent( ) and SBS.ChargingVoltage( ) are set to the appropriate value per the charging
algorithm and SBS.OperationStatus( ) [XDSG] and SBS.SafetyStatus( ) [CUV] are reset.
However, when the bq20z80 has the SBS.SafetyStatus( ) [CUV] bit set, the discharge FET is turned on again if
SBS.Current( ) is reported to be ≥ DF:Chg Current Threshold. No other flags change state until full recovery is
reached. This prevents overheating the discharge-FET body diode during charging from an undervoltage
condition.
SIZE
(BYTES)
DEFAULT
VALUE
NAME
CLASS / SUBCLASS
FORMAT
VALID RANGE
UNITS
CUV Threshold
CUV Recovery
CUV Time
0 to 3500
0 to 3600
0 to 60
2
2
1
2200
3000
2
mV
s
1st Level Safety / Voltage (0)
Integer
Pack Undervoltage
The bq20z80 can disable discharging by turning off the discharge FET if SBS.Voltage( ) is ≤ DF:PUV Threshold
for a time period ≥ DF:PUV Time. This feature is disabled if DF:PUV Time = 0.
During the period between the time when a low voltage is first detected and the expiration of DF:PUV Time,
SBS.SafetyAlert( ) [PUV] is set. If, during this period, the voltage rises above the DF:PUV Threshold, this flag is
cleared.
If DF:PUV Time expires, the discharge FET is turned off and the ZVCHG FET is turned on if DF:Operation Cfg A
[ZVCHG1, ZVCHG0] are set appropriately. Also when DF:PUV Time expires SBS.BatteryStatus( ) [TDA,FD]are
set, SBS.ChargingCurrent( ) is set to DF:Pre-Charge Current, SBS.OpertionStatus( ) [XDSG] is set and
SBS.SafetyStatus( ) [PUV] is set.
13
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