BQ27541 Datasheet, PDF (28/38 Pages) Texas Instruments – Single Cell Li-Ion Battery Fuel Gauge for Battery Pack Integration

bq27541
SLUS861 – DECEMBER 2008 ........................................................................................................................................................................................... www.ti.com
The gauge will remain in HIBERNATE mode until communication activity appears on the communication lines
Upon exiting HIBERNATE mode, the [HIBERNATE] bit of CONTROL_STATUS is cleared.
Because the fuel gauge is dormant in HIBERNATE mode, the battery should not be charged or discharged in this
mode, because any changes in battery charge status will not be measured. If necessary, the host equipment can
draw a small current (generally infrequent and less than 1mA, for purposes of low-level monitoring and updating);
however, the corresponding charge drawn from the battery will not be logged by the gauge. Once the gauge
exits to NORMAL mode, the IT algorithm will re-establish the correct battery capacity, regardless of the total
charge drawn in HIBERNATE mode.
If a charger is attached, the host should immediately take the fuel gauge out of HIBERNATE mode before
beginning to charge the battery. Charging the battery in HIBERNATE mode will result in a notable gauging error
that will take several hours to correct.
POWER CONTROL
Reset Functions
When the bq27541 detects a software reset ([RESET] bit of Control( ) initiated), it determines the type of reset
and increments the corresponding counter. This information is accessible by issuing the command Control( )
function with the RESET_DATA subcommand.
As shown in Figure 4 if a partial reset was detected, a RAM checksum is generated and compared against the
previously stored checksum. If the checksum values do not match, the RAM is reinitialized (a Full Reset). The
stored checksum is updated every time RAM is altered.
DEVICE RESET
Generate Active
RAM checksum
value
Stored
checksum
NORMAL
OPERATION
NO
Do the Checksum
Values Match?
YES
Active RAM
NO
changed ?
Store
checksum
YES
Generate new
checksum value
Re-initialize all
RAM
Figure 4. Partial Reset Flow Diagram
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