BQ24100 Datasheet, PDF (17/26 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

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bq24100, bq24103
bq24105, bq24108
bq24113, bq24115
SLUS606C – JUNE 2004 – REVISED SEPTEMBER 2005
Battery Absent Detection
For applications with removable battery packs, bqSWITCHER provides a battery absent detection scheme to
reliably detect insertion and/or removal of battery packs.
POR or V_RCH
Yes
Detection routine runs on power up
and if V_BAT drops below refresh
threshold due to removing battery
or discharging battery.
Enable
I_(DETECT)
for t_(DETECT)
V_I(BAT)<V_(LOWV)
No
Yes
Apply I_(WAKE)
for t_(WAKE)
BATTERY
PRESENT,
Begin Charge
V_I(BAT) >
V_O(REG)
-V_RCH
Yes
BATTERY
ABSENT
BATTERY
No
PRESENT,
Begin Charge
Figure 9. Battery Absent Detection for bq2410x ICs only
The voltage at the BAT pin is held above the battery recharge threshold, V_RCH, by the charged battery following
fast charging. When the voltage at the BAT pin falls to the recharge threshold, either by a load on the battery or
due to battery removal, the bqSWITCHER begins a battery absent detection test. This test involves enabling a
detection current, I_DETECT, for a period of t_DETECT and checking to see if the battery voltage is below the precharge
threshold, V_LOWV. Following this, the precharge current, I_OPRECHG is applied for a period of t_DETECT and the battery
voltage is checked again to ensure that it is above the recharge threshold. The purpose of this current is to
attempt to close a battery pack with an open protector, if one is connected to the bqSWITCHER.
Passing both of the discharge and charging tests indicates a battery absent fault at the STAT pins. Failure of
either test starts a new charge cycle. For the absent battery condition, the voltage on the BAT pin rises and falls
between the V_LOWV and V_OREG thresholds indefinitely.
Timer Fault Recovery
As shown in Figure 5, bqSWITCHER provides a recovery method to deal with timer fault conditions. The
following summarizes this method.
Condition 1 V_I(BAT) above recharge threshold (V_OREG - V_RCH) and timeout fault occurs.
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