www.ti.com
5.7 POWER MODES
5.7.1 NORMAL MODE
5.7.2 SLEEP MODE
5.7.3 BAT INSERT CHECK MODE
bq27500bq27501System-Side Impedance Track™ Fuel Gauge
SLUS785 – SEPTEMBER 2007
The bq27500/1 has four power modes: NORMAL, SLEEP, HIBERNATE, and BAT INSERT CHECK. InNORMAL mode, the bq27500/1 is fully powered and can execute any allowable task. In SLEEP mode, thefuel gauge exists in a reduced-power state, periodically taking measurements and performing calculations.In HIBERNATE mode, the fuel gauge is in its lowest power state, but can be woken up by communicationactivity or certain I/O activity. Finally, the BAT INSERT CHECK mode is a powered-up, but low-powerhalted, state, where the bq27500/1 resides when no battery is inserted into the system.
The relationship between these modes is shown in Figure 5-2 .
The fuel 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 isupdated. Decisions to change states are also made. This mode is exited by activating a different powermode.
Because the gauge consumes the most power in NORMAL mode, the Impedance Track™ algorithmminimizes the time the fuel gauge remains in this 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 modehas been qualified, but prior to entering it, the bq27500/1 performs an ADC autocalibration to minimizeoffset.
During SLEEP mode, the bq27500/1 periodically takes data measurements and updates its data set.However, a majority of its time is spent in an idle condition.
The bq27500/1 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent( ) risesabove Sleep Current, or (2) a current in excess of I
WAKE
through R
SENSE
is detected.
In the event that a battery is removed from the system while a charger is present (and powering thegauge), Impedance Track™ updates are not necessary. Hence, the fuel gauge enters a state that checksfor battery insertion and does not continue executing the Impedance Track™ algorithm.
This mode is a halted-CPU state that occurs when an adapter, or other power source, is present to powerthe bq27500/1 (and system), yet no battery has been detected. When battery insertion is detected, aseries of initialization activities begin, which include: OCV measurement, setting the BAT_GD pin, andselecting the appropriate battery profiles.
Some commands, issued by a system processor, can be processed while the bq27500/1 is halted in thismode. The gauge will wake up to process the command, then return to the halted state awaiting batteryinsertion.
Submit Documentation Feedback FUNCTIONAL DESCRIPTION 27