BQ24100_10 Datasheet, PDF (16/40 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs ( bqSWITCHER™)

bq24100, bq24103, bq24103A
bq24104, bq24105, bq24108, bq24109
bq24113, bq24113A, bq24115
SLUS606O – JUNE 2004 – REVISED MARCH 2010
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Charge Termination and Recharge
The bqSWITCHER monitors the charging current during the voltage regulation phase. Once the termination
threshold, I_TERM, is detected, the bqSWITCHER terminates charge. The termination current level is selected by
the value of programming resistor, R_(ISET2), connected to the ISET2 pin.
ǒ ITERM + K(ISET2)
R_(ISET2)
V_TERM
Ǔ _R(SNS)
(7)
where
R_(SNS) is the external current-sense resistor
V_TERM is the output of the ISET2 pin
K_(ISET2) is the A/V gain factor
V_TERM and K_(ISET2) are specified in the Electrical Characteristics table
As a safety backup, the bqSWITCHER also provides a programmable charge timer. The charge time is
programmed by the value of a capacitor connected between the TTC pin and GND by the following formula:
t_CHARGE + C_(TTC) K_(TTC)
(8)
where
C_(TTC) is the capacitor connected to the TTC pin
K_(TTC) is the multiplier
A new charge cycle is initiated when one of the following conditions is detected:
• The battery voltage falls below the V_RCH threshold.
• Power-on reset (POR), if battery voltage is below the V_RCH threshold
• CE toggle
• TTC pin, described as follows.
In order to disable the charge termination and safety timer, the user can pull the TTC input below the V_{TTC_EN}
threshold. Going above this threshold enables the termination and safety timer features and also resets the timer.
Tying TTC high disables the safety timer only.
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