BQ27541-V200_17 Datasheet, PDF (26/46 Pages) Texas Instruments – Single Cell Li-Ion Battery Fuel Gauge for Battery Pack Integration

bq27541-V200
Not Recommended for New Designs
SLUSA11B – FEBRUARY 2010 – REVISED SEPTEMBER 2013
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Max DeltaV, Min DeltaV
Maximal / Minimal value allowed for delta V, which will be subtracted from simulated voltage during remaining
capacity simulation.
Qmax Max Delta %
Maximal change of Qmax during one update, as percentage of Design Capacity. If the gauges attempts to
change Qmax exceeds this limit, changed value will be capped to old value ± DesignCapacity*QmaxMaxDelta /
100
DeltaV Max Delta
Maximal change of Delta V value. If attempted change of the value exceeds this limit, change value will be
capped to old value ±DeltaV Max Delta
Lifetime Data Logging Parameters
The Lifetime Data logging function helps development and diagnosis with the bq27541. Note that IT_ENABLE
needs to be enabled (Command 0x0021) for lifetime data logging functions to be active. bq27541 logs the
lifetime data as specified in the Lifetime Data and Lifetime Temp Samples data Flash Subclasses. The data
log recordings are controlled by the Lifetime Resolution data flash Subclass.
The Lifetime Data Logging can be started by setting the IT_ENABLE bit and setting the Update Time register to a
non-zero value.
Once the Lifetime Data Logging function is enabled, the measured values are compared to what is already
stored in the Data Flash. If the measured value is higher than the maximum or lower than the minimum value
stored in the Data Flash by more than the "Resolution" set for at least one parameter, the entire Data Flash
Lifetime Registers are updated after at least LTUpdateTime.
LTUpdateTime sets the minimum update time between DF writes. When a new max/min is detected, a LT
Update window of [update time] second is enabled and the DF writes occur at the end of this window. Any
additional max/min value detected within this window will also be updated. The first new max/min value detected
after this window will trigger the next LT Update window.
Internal to bq27541, there exists a RAM max/min table in addition to the DF max/min table. The RAM table is
updated independent of the resolution parameters. The DF table is updated only if at least one of the RAM
parameters exceeds the DF value by more than resolution associated with it. When DF is updated, the entire
RAM table is written to DF. Consequently, it is possible to see a new max/min value for a certain parameter even
if the value of this parameter never exceeds the maximum or minimum value stored in the Data Flash for this
parameter value by the resolution amount.
The Life Time Data Logging of one or more parameters can be reset or restarted by writing new default (or
starting) values to the corresponding Data Flash registers through sealed or unsealed access as described
below. However, when using unsealed access, new values will only take effect after device reset
The logged data can be accessed as R/W in unsealed mode from Lifetime Data SubClass (SubClass ID=59) of
Data Flash. Lifetime data may be accessed (R/W) when sealed using a process identical Manufacturer Info Block
B and C. The DataFlashBlock command code is 4. Note only the first 32 bytes of lifetime data (not resolution
parameters) can be R/W when sealed. See Manufacturers Info Block section for sealed access. The logging
settings such as Temperature Resolution, Voltage Resolution, Current Resolution, and Update Time can be
configured only in unsealed mode by writing to the Lifetime Resolution Subclass (SubClassID=66) of the Data
Flash.
The Lifetime resolution registers contain the parameters which set the limits related to how much a data
parameter must exceed the previously logged Max/Min value to be updated in the lifetime log. For example, V
must exceed MaxV by more than Voltage Resolution to update MaxV in the Data Flash.
DETAILED PIN DESCRIPTIONS
System Shutdown Enable (SE Pin)
By using SE pin, the fuel gauge can be made to power-off through an external circuit. This feature is useful to
shutdown the fuel gauge in a deeply discharged battery to protect the battery.
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