BQ2084-V140_14 Datasheet, PDF (25/64 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE FOR USE WITH THE bq29312

bq2084-V140
www.ti.com
SLUS664B – JULY 2005 – REVISED AUGUST 2006
Low-Power Modes
The bq2084-V140 enters sleep mode when the charge and discharge current is less than the threshold
programmed in Sleep Current Threshold DF 0xfc, the SMBus lines are low for at least 2s, and bit 12 of Misc.
Configuration DF 0x2a is set to zero. Additionally, PRES must be pulled high if the NR bit in Misc Config is set to
0. The bq2084-V140 wakes up periodically to monitor voltage and temperature and to apply self-discharge
adjustment. The sleep period is set in Sleep Timer DF 0xfe. The bq2084-V140 wakes up at a period set by
Sleep Current Multiplier DF 0xfd multiplied by Sleep Time to measure current. The bq2084-V140 comes out of
sleep when either of the SMBus lines go high or when the current is measured and it is greater than the Sleep
Current Threshold.
The sleep current threshold, SLP (mA), is stored in Sleep Current Thresh DF 0xfc as:
Sleep Current Thresh = SLP(mA)/0.5
The wake-up period for current measurement, WAT(s), is set using the following formula:
Sleep Current Multiplier x Sleep Time = WAT(s)
During sleep mode, both charge and discharge FETs are turned off if the NR bit in Misc Config is cleared. If the
bq2084-V140 is in Non-Removable mode where NR=1, then the discharge FET retains its state on entry to
sleep.
Shutdown Mode
The bq2084-V140 goes into shutdown, in which all FETs are turned off and the pack electronics are powered
down (including the bq2084-V140), when SBS.Voltage() falls below Shutdown Voltage DF 0x7c-0x7d and
Voltage at the Pack pin is less than VPACK threshold (DF 0x131, 0x132) both for 2 consecutive samples (1 to 2
s).
Vpack is programmed in units of 0.935 mV/count and has tolerance of ±6%. For example, to set 12 V as Vpack
Threshold, the program value should be 12000/0.935 = 12834.
When the DSG FET is turned on, the pack voltage is close to the battery voltage even with no charger attached.
Therefore, to enter shutdown, the Vpack threshold should be set higher than the shutdown threshold plus the
tolerance.
The bq2084-V140 can also be instructed to enter Shutdown mode via the ManufacturerAccess() command.
When the command is sent to the bq2084-V140, the bq29312 is instructed to enter shutdown mode by the
bq2084-V140. This forces the chipset into its lowest power mode. The bq2084-V140 does not issue a shutdown
command to the AFE unless the pack voltage is less than the Vpack Threshold. Program the Vpack threshold
higher than the SBS.Voltage() when ship command is issued. Exit from this mode is only achieved by
application of a charger.
After exiting shutdown mode, the bq2084-V140 does not enter the shutdown mode again until the Shutdown
Timer (DF 0x133, units are seconds) has expired even if the correct conditions are present. After the Shutdown
Timer has expired, the SMBus command or voltage and current conditions enables the bq2084-V140 to enter
shutdown mode.
Submit Documentation Feedback
25