Not Recommended for New Designs

bq28550-R1

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SLUSAS4A – OCTOBER 2012 – REVISED SEPTEMBER 2014

NOTE

When the battery is connected for the first time, discharging may not be enabled. For this

case, the following procedure is required:

•

Short the VM pin and Vss pin, or

•

Connect the charger to the system such that the IC returns to normal status.

7.6.5.2 SLEEP Mode

SLEEP mode is entered automatically if the feature is enabled (Operation Configuration [SLEEP]) = 1) and

AverageCurrent() is below the programmable level Sleep Current. Once entry into SLEEP mode has been

qualified, but prior to entering it, the bq28550-R1 device performs an ADC auto-calibration to minimize offset.

While in SLEEP mode, the gas gauge can suspend serial communications as much as 4 ms by holding the

comm line(s) low. This delay is necessary to correctly process host communication, because the gas gauge

processor is mostly halted in SLEEP mode.

During SLEEP mode, the bq28550-R1 device periodically takes data measurements and updates its data set.

However, a majority of its time is spent in an idle condition. The bq28550-R1 device exits SLEEP if any entry

condition is broken, specifically when (1) AverageCurrent() rises above Sleep Current, or (2) a current in excess

7.6.5.3 FULLSLEEP Mode

FULLSLEEP mode is entered automatically if the feature is enabled by setting the Configuration [FULLSLEEP]

bit in the Control Status register when the bq28550-R1 device is in SLEEP mode. The gauge exits FULLSLEEP

mode when there is any communication activity. Therefore, the execution of SET_FULLSLEEP sets the

[FULLSLEEP] bit, but EVSW might still display the bit clear. FULLSLEEP mode can be verified by measuring the

current consumption of the gauge. In this mode, the high frequency oscillator is turned off. The power

consumption is further reduced in this mode compared to the SLEEP mode.

FULLSLEEP mode can also be entered by setting the Full Sleep Wait Time to be a number larger than 0.

FULLSLEEP will be entered when the timer counts down to 0. This feature is disabled when the data flash is set

as 0.

During FULLSLEEP mode, the bq28550-R1 device periodically takes data measurements and updates its data

set. However, a majority of its time is spent in an idle condition.

The bq28550-R1 device exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent()

While in FULLSLEEP mode, the gas gauge can suspend serial communications as much as 4 ms by holding the

comm line(s) low. This delay is necessary to correctly process host communication, because the gas gauge

processor is mostly halted in SLEEP mode.

7.6.5.3.1

Clearing FULLSLEEP Mode

FULLSLEEP mode will stay on permanently if Full Sleep Wait Time is not set to 0.

Clearing FULLSLEEP mode:

•

If Full Sleep Wait Time is set to 0, the CLEAR condition clears the flag. If it is not set to 0, the CLEAR

condition resets the timer.

•

communication while not in FULLSLEEP will NOT clear the flag. This means if there is current flowing when

the FULLSLEEP command is sent, there is no way to clear it until after the device enters SLEEP mode.

7.6.5.4 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 gas gauge can enter HIBERNATE due to either low cell voltage or low load current.

•

HIBERNATE due to the load current—If the gas gauge enters HIBERNATE mode due to the load current, the

[HIBERNATE] bit of the CONTROL_STATUS register must be set. The gauge waits to enter HIBERNATE

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