Datasheet

SystemSleep
ExitFromSLEEP
| AverageCurrent() | > SleepCurrent
OR
CurrentisDetectedaboveI
WAKE
ExitFrom SLEEP
(Hosthasset ControlStatus
[HIBERNATE]= 1
OR
V
CELL
< HibernateVoltage
Fuel gauginganddata
updatedevery 1s
NORMAL
Fuel gauginganddata
updated every 20 seconds
(LFOONandHFOOFF)
SLEEP
Disableallbq27505
subcircuitsexceptGPIO.
NegateBAT_GD
HIBERNATE
EntrytoSLEEP
OperationConfiguration[SLEEP]= 1
AND
| AverageCurrent() | ≤ SleepCurrent
AND
ControlStatus[SNOOZE]= 0
Wakeup From HIBERNATE
Communication Activity
AND
CommaddressisNOT forbq27505
ExitFrom HIBERNATE
BatteryRemoved
POR
Checkforbatteryinsertion
fromHALT state.
Nogauging
BAT INSERT CHECK
EntrytoNORMAL
Flags [BAT _DET]= 1
ExitFrom NORMAL
Flags [BAT _DET]= 0
ExitFrom SLEEP
Flags [ BAT_DET]= 0
Flags [BAT _DET]= 0
WAIT_HIBERNATE
Fuel gauginganddata
updated every 20 seconds
BAT_GDunchanged
ExitFromWAIT_HIBERNATE
Cellrelaxed
AND
| AverageCurrent() |< Hibernate
Current
OR
Cellrelaxed
AND
V
CELL
< HibernateVoltage
SystemShutdown
ExitFrom WAIT_HIBERNATE
HostmustsetControlStatus
[HIBERNATE] = 0
AND
V
CELL
> HibernateVoltage
ExitFrom HIBERNATE
Communication Activity
ANDCommaddressisforbq27505
bq27505 clearsControlStatus
[HIBERNATE] = 0
RecommendHostalsoset Control
Status [HIBERNATE] = 0
Fuel gauginganddata
updated every 20 seconds
BothLFOandHFOareON
SLEEP+
EntrytoSLEEP+
OperationConfiguration[SLEEP]= 1
AND
ControlStatus[SNOOZE]= 1
AND
| AverageCurrent() | ≤ SleepCurrent
ExitFromSLEEP+
Anycommunicationtothegauge
OR
| AverageCurrent() | > SleepCurrent
OR
CurrentisDetectedaboveI
WAKE
EntrytoSLEEP+
ControlStatus[SNOOZE]= 0
EntrytoSLEEP+
ControlStatus[SNOOZE]= 1
Not Recommended for New Designs
bq27505
SLUS884–FEBRUARY 2009 www.ti.com
5.3.4 Power Path Control With the BAT_GD Pin
The bq27505 must operate in conjunction with other electronics in a system appliance, such as chargers
or other ICs and application circuits that draw appreciable power. After a battery is inserted into the
system, there should be no charging current or a discharging current higher than C/20, so that an accurate
OCV can be read. The OCV is used for helping determine which battery profile to use, as it constitutes
part of the battery impedance measurement
When a battery is inserted into a system, the Impedance Track™ algorithm requires that no charging of
the battery takes place and that any discharge is limited to less than C/20—these conditions are sufficient
for the fuel gauge to take an accurate OCV reading. To disable these functions, the BAT_GD pin is merely
negated from the default setting. Once an OCV reading has be made, the BAT_GD pin is asserted,
thereby enabling battery charging and regular discharge of the battery. The Operation Configuration
[BATG_POL] bit can be used to set the polarity of the battery good signal, should the default configuration
need to be changed.
Figure 5-1. Power Mode Diagram
Figure 5-1 details how the BAT_GD pin functions in the context of battery insertion and removal, as well
as NORMAL vs. SLEEP modes.
28 FUNCTIONAL DESCRIPTION Copyright © 2009, Texas Instruments Incorporated
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