Exit From SLEEP

Pack Configuration [SLEEP ] =0

OR

| AverageCurrent( ) | > Sleep Current

OR

Current is Detected above IWAKE

Fuel gauging and data

updated every 1 s

NORMAL

Fuel gauging and data

updated every 20 seconds

SLEEP

Disable all gas gauge

subcircuits except GPIO

HIBERNATE

Wakeup From HIBERNATE

Communication Activity

AND

Comm address is NOT for the gas gauge

Exit From HIBERNATE

POR

Exit From WAIT_ HIBERNATE

Cell relaxed

AND

| AverageCurrent () | < Hibernate

Current

OR

Cell relaxed

AND

V

System HIBERNATION

Exit From HIBERNATE

Communication Activity

OR

the gas gauge clears Control Status

[ HIBERNATE ] = 0

Recommend Host also set Control

Status [ HIBERNATE] = 0

WAIT_HIBERNATE

Fuel gauging and data

updated every 20 s

In low-power state of SLEEP

.

mode Gas gauging and data

are updated every 20 s.

FULLSLEEP

System SLEEP

FULLSLEEP Count Down

WAITFULLSLEEP

Entry to FULLSLEEP

Host must set Control Status

[FULLSLEEP] = 1

Exit From FULLSLEEP

Any Communication Cmd

Exit From WAITFULLSLEEP

Any Communication Cmd

Entry to WAITFULLSLEEP

Full Sleep Wait Time > 0

Entry to FULLSLEEP

Count < 1

Exit From SLEEP

(Host has set Control Status

[HIBERNATE ] = 1

OR

<

Hibernate Voltage

_

Exit From WAIT HIBERNATE

Host must set Control Status

[ HIBERNATE ] = 0

AND

>

Hibernate Voltage

Entry to SLEEP

Pack Configuration[ SLEEP] = 1

AND

| AverageCurrent( ) | =Sleep Current

Fuel Gauge is OFF

V

= 0 V

SHUTDOWN

Entry to SHUTDOWN

No Charger Present

System SHUTDOWN

PRE-SHUTDOWN

Fuel Gauging stopped

Discharge FET opened

IBAT = Hibernate

Entry to PRE-SHUTDOWN

[ SHUTDOWN ] = 1

Exit from PRE-SHUTDOWN

Communication Activity

OR

Current Detected >

IWAKE

Exit from SHUTDOWN

Charger Detected

AND

Protection FETs closed

V

BAT

BAT

V

BAT

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.

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.

20

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