bq20z80-V101
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SLUS625D–SEPTEMBER 2004–REVISED OCTOBER 2005
Permanent Failure Flags
When any NEW cause of PF is detected in SBS.PFStatus( ), the NEW cause is added to DF:PF Flag 1. This
allows DF:PF Flag 1 to show ALL of the different permanent failure conditions that have occurred.
On the first occasion of SBS.PFStatus( ) changing from 0x00 the value is stored to DF:PF Flag 2.
Clearing Permanent Failure
The bq20z80 permanent failure mode can be cleared by sending two SBS.ManufacturerAccess( ) commands in
sequence. See SBS.ManufacturerAccess( ) for more details.
Safety Overvoltage Protection
The bq20z80 reports a safety-overvoltage condition when SBS.Voltage( ) is ≥ the DF:SOV Threshold for a period
≥ DF:SOV Time. During the time between when the excessive voltage is first detected and the expiration of
DF:SOV TimeSBS.PFAlert( ) [SOV] is set.
If DF:Permanent Fail Cfg [XSOV] is set, the SAFE pin is driven low and the SAFE pin is driven high. If DF:SOV
Time is set to 0, this feature is disabled.
SIZE
(BYTES)
DEFAULT
VALUE
NAME
CLASS / SUBCLASS
FORMAT
VALID RANGE
UNITS
SOV Threshold
SOV Time
0 to 20000
0 to 30
2
1
mV
s
18000
2nd Level Safety / Voltage (16)
Integer
0 (4 typical)
Cell Imbalance Fault Protection
The bq20z80 reports a cell imbalance condition when SBS.Current( ) is ≤ DF:Cell Imbalance Current for a
period of DF:Battery Rest Time, AND the difference between the highest measured cell voltage
(SBS.CellVoltagex( )MAX) and lowest measured cell voltage (SBS.CellVoltagex( )MIN) is ≥ DF:Cell Imbalance
Fail Voltage for a period ≥ DF:Cell Imbalance Time.
During the time between when excessive cell-voltage variance is first detected and the expiration of DF:Cell
Imbalance Time, SBS.PFAlert( ) [CIM] is set.
If DF:Permanent Fail Cfg [XCIM] is set, the SAFE pin is driven low and the SAFE pin is driven high. If DF:Cell
Imbalance Time is set to 0, this feature is disabled.
CLASS /
SUBCLASS
SIZE (BYTES)
NAME
FORMAT
VALID RANGE
UNITS
DEFAULT VALUE
Cell Imbalance Fail Voltage
Cell Imbalance Time
Cell Imbalance Current
Battery Rest Time
0 to 5000
0 to 30
2
1
1
1
mV
s
1000
0 (4 typical)
2nd Level Safety/
Voltage (16)
Integer
0 to 200
0 to 240
mA
s
5
60
2nd Level Protection IC Input
The PFIN input of the bq20z80 can be used to determine the state of an external protection device such as the
bq29400. If this pin is logic low for a period of time ≥ DF:PFIN Detect Time, the Permanent Failure Mode is
entered. During the time between when PFIN is detected low and the expiration of DF:PFIN Detect
TimeSBS.PFAlert( ) [PFIN] is set.
If DF:Permanent Fail Cfg [XPFIN] is set, the SAFE pin is driven low and the SAFE pin is driven high. Also, if
DF:PFIN Detect Time is set to 0, this feature is disabled.
NAME
CLASS / SUBCLASS
FORMAT
VALID RANGE SIZE (BYTES)
0 to 30
UNITS
DEFAULT VALUE
PFIN Detect Time
2nd Level Safety / Voltage (16)
Integer
1
s
0 (4 typical)
21
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