BQ2406X Datasheet, PDF (20/31 Pages) Texas Instruments – 1A SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION

bq2406x
SLUS689 – JUNE 2006
www.ti.com
The termination function is DISABLED:
1. In bq24060/61/62/64/65 the termination is disabled when the TMR pin is left open (floating).
2. In bq24063 leaving TMR pin open (floating) does NOT disable the termination. The only way to disable
termination in the bq24063 is to set TE = HIGH.
BATTERY ABSENT DETECTION – VOLTAGE MODE ALGORITHM
The bq2406x provides a battery absent detection scheme to reliably detect insertion and/or removal of battery
packs. The detection circuit applies an internal current to the battery terminal, and detects battery presence
based on the terminal voltage behavior. Figure 10 has a typical waveform of the output voltage when the battery
absent detection is enabled and no battery is connected:
5
4.50
4
3.50
3
2.50
2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
t - Time - s
Figure 10. Battery-Absent Detection Waveforms
The battery absent detection function is disabled if the voltage at the BAT pin is held above the battery recharge
threshold, V_(RCH), after termination detection. When the voltage at the BAT pin falls to the recharge threshold,
either by connection of a load to the battery or due to battery removal, the bq2406x 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 pre-charge threshold, V_(LOWV). Following this, the precharge current,
I_O(PRECHG) is applied for a period of T_(DETECT) and the battery voltage checked again to be above the recharge
threshold.
Passing both of the discharge and charging tests (battery terminal voltage being below the pre-charge and
above the recharge thresholds on the battery detection test) indicates a battery absent fault at the STAT1 and
STAT2 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_O(REG) thresholds indefinitely. See the operation flowchart for
more details on this algorithm.
The battery absent detection function is disabled when the termination is disabled.
The bq2406x provides a small battery leakage current, IBAT(DONE) (1 µA typical), after termination to pull down
the BAT pin voltage in the event of battery removal. If the leakage on the OUT pin is higher than this pulldown
current, then the voltage at the pin remains above termination and a battery-absent state will not be detected.
This problem is fixed with the addition of a pulldown resistor of 2 MΩ to 4 MΩ from the OUT pin to VSS. A
resistor too large (> 4 MΩ) can cause the OUT pin voltage to drop below the V(LOWV) threshold before the
recharge deglitch (typ 25 ms) expires, causing a fault condition. In this case the bq2406x provides a fault current
(typ 750 µA) to pull the pin above the termination threshold.
20
Submit Documentation Feedback