BQ27541 Datasheet, PDF (27/38 Pages) Texas Instruments – Single Cell Li-Ion Battery Fuel Gauge for Battery Pack Integration

bq27541
www.ti.com ........................................................................................................................................................................................... SLUS861 – DECEMBER 2008
While in FULLSLEEP mode, the fuel gauge can suspend serial communications as much as 4ms by holding the
comm line(s) low. This delay is necessary correctly process host communication, since the fuel gauge processor
is mostly halted in SLEEP mode.
POR
Exit From HIBERNATE
VCELL < POR threshold
Exit From HIBERNATE
Communication Activity
AND Comm address is for bq27541
OR
bq27541 clears Control Status
[HIBERNATE] = 0
Recommend Host also set Control
Status [HIBERNATE] = 0
NORMAL
Fuel gauging and data
updated every 1s
Exit From SLEEP
Pack Configuration [SLEEP] = 0
OR
| AverageCurrent( ) | > Sleep Current
OR
Current is Detected above IWAKE
HIBERNATE
Disable all bq27541
subcircuits except GPIO.
Wakeup From HIBERNATE
Communication Activity
AND
Comm address is NOT for bq27541
Exit From WAIT_HIBERNATE
Cell relaxed
AND
| AverageCurrent() | < Hibernate
Current
OR
Cell relaxed
AND
VCELL < Hibernate Voltage
WAIT_HIBERNATE
Fuel gauging and data
updated every 20 seconds
System Shutdown
Entry to SLEEP
Pack Configuration [SLEEP] = 1
AND
| AverageCurrent( ) |≤ Sleep Current
SLEEP
Fuel gauging and data
updated every 20 seconds
Exit From WAIT_HIBERNATE
Host must set Control Status
[HIBERNATE] = 0
AND
VCELL > Hibernate Voltage
Exit From SLEEP
(Host has set Control Status
[HIBERNATE] = 1
OR
VCELL < Hibernate Voltage
Entry to WAITFULLSLEEP
Full Sleep Wait Time > 0
Exit From WAITFULLSLEEP
Any Communication Cmd
WAITFULLSLEEP
FULLSLEEP Count Down
Entry to FULLSLEEP
Host must set Control Status
[FULLSLEEP] = 1
Entry to FULLSLEEP
Count <1
FULLSLEEP
Exit From
FULLSLEEP
Any
Communication
Cmd
In low power state of SLEEP
mode. Gas gauging and data
updated every 20 seconds
System Sleep
Figure 3. Power Mode Diagram
HIBERNATE Mode
HIBERNATE mode should be used when the host system needs to enter a low-power state, and minimal gauge
power consumption is required. This mode is ideal when the host is set to its own HIBERNATE, SHUTDOWN, or
OFF modes. The fuel gauge can enter HIBERNATE due to either low cell voltage or low load current.
– HIBERNATE due to the cell voltage. When the cell voltage drops below the Hibernate Voltage and a valid OCV
measurement has been taken, the fuel gauge enters HIBERNATE mode. The [HIBERNATE] bit of the
CONTROL register has no impact for the fuel gauge to enter the HIBERNATE mode. If the [SHUTDOWN] bit of
CONTROL _STATUS is also set, the SE pin will be released, thereby allowing an optional external circuit to
remove power from the gauge LDO.
– HIBERNATE due to the load current. If the fuel gauge enters the HIBERNATE mode due to the load current,
the [HIBERNATE] bit of the CONTROL_STATUS register must be set. The gauge waits to enter HIBERNATE
mode until it has taken a valid OCV measurement and the magnitude of the average cell current has fallen below
Hibernate Current.
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Product Folder Link(s): bq27541
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