BQ28550-R1 Datasheet, PDF (20/42 Pages) Texas Instruments – Single Cell Li-Ion Battery Gas Gauge

Not Recommended for New Designs
bq28550-R1
SLUSAS4A – OCTOBER 2012 – REVISED SEPTEMBER 2014
www.ti.com
7.6.4.1.2 Key Programming (The Secure Memory Key)
As the name suggests, the bq28550-R1 secure-memory authentication key is stored in the secure memory of the
bq28550-R1 device. If a secure-memory key has been established and the Data Flash Key is
0x00000000000000000000000000000000, only this key can be used for authentication challenges (the
programmable data flash key is not available). The selected key can only be established/programmed by special
arrangements with TI, using TI’s Secure B-to-B Protocol. The secure-memory key can never be changed or read
from the bq28550-R1 device.
7.6.5 Device Functional Modes
The bq28550-R1 device has four power modes: NORMAL, SLEEP, HIBERNATE, and SHUTDOWN. In NORMAL
mode, the bq28550-R1 device is fully powered and can execute any allowable task. In SLEEP mode, the gas
gauge exists in a reduced-power state, periodically taking measurements and performing calculations. In
HIBERNATE mode, the gas gauge is in a low power state, but can be awakened by communication or certain I/O
activity. The device enters SHUTDOWN mode if there is a UVP condition detected or power down of the system.
The relationship between these modes is shown in Figure 3. Details are described in the sections that follow.
POR
Exit From HIBERNATE
VBAT < POR threshold
NORMAL
Fuel gauging and data
updated every 1 s
Exit From HIBERNATE
Communication Activity
OR
the gas gauge clears Control Status
[ HIBERNATE ] = 0
Entry to SLEEP
Pack Configuration[ SLEEP] = 1
Recommend Host also set Control
AND
Status [HIBERNATE] = 0
| AverageCurrent( ) | =Sleep Current
Exit From SLEEP
Pack Configuration [SLEEP ] =0
OR
| AverageCurrent( ) | > Sleep Current
OR
Current is Detected above IWAKE
Exit from SHUTDOWN
Charger Detected
AND
Protection FETs closed
HIBERNATE
SLEEP
SHUTDOWN
Disable all gas gauge
subcircuits except GPIO
Fuel gauging and data
updated every 20 seconds
Wakeup From HIBERNATE
Exit From WAIT_ HIBERNATE
Cell relaxed
AND
| AverageCurrent () | < Hibernate
Current
OR
Cell relaxed
VBAT _<
AND
Hibernate Voltage
WAIT_ HIBERNATE
Communication Activity
AND
Comm address is NOT for the gas gauge
Entry to WAITFULLSLEEP
Full Sleep Wait Time > 0
Exit From WAITFULLSLEEP
Any Communication Cmd
WAITFULLSLEEP
FULLSLEEP Count Down
Exit From WAIT H_ IBERNATE
Host must set Control Status
[ HIBERNATE ] = 0
Entry to FULLSLEEP
VBAT
AND
> Hibernate
Voltage
Host must set Control Status
[FULLSLEEP] = 1
Entry to FULLSLEEP
Count < 1
Exit From FULLSLEEP
Any Communication Cmd
FULLSLEEP
Fuel gauging and data
updated every 20 s
System HIBERNATION
Exit From SLEEP
(Host has set Control Status
[HIBERNATE ] = 1
OR
VBAT < Hibernate Voltage
In low-power state of SLEEP
mode. Gas gauging and data
are updated every 20 s.
System SLEEP
Exit from PRE-SHUTDOWN
Communication Activity
OR
Current Detected > IWAKE
Fuel Gauge is OFF
VBAT = 0 V
Entry to SHUTDOWN
No Charger Present
Entry to PRE-SHUTDOWN
[SHUTDOWN ] = 1
PRE - SHUTDOWN
Fuel Gauging stopped
Discharge FET opened
IBAT = Hibernate
System SHUTDOWN
Figure 3. Power Mode Diagram
7.6.5.1 NORMAL Mode
The gas gauge is in NORMAL mode when not in any other power mode. During this mode, AverageCurrent(),
Voltage(), and Temperature() measurements are taken, and the interface data set is updated. Decisions to
change states are also made. This mode is exited by activating a different power mode.
Because the gauge consumes the most power in NORMAL mode, the algorithm minimizes the time the gas
gauge remains in this mode.
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