BQ24200DGNG4 Datasheet, PDF (11/20 Pages) Texas Instruments – SINGLE-CHIP LI-ION AND LI-POL CHARGE MANAGEMENT IC FOR CURRENT-LIMITED APPLICATIONS

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bq24200, bq24201
bq24202, bq24203
bq24204, bq24205
SLUS501C – OCTOBER 2001 – REVISED MARCH 2008
ǒ₅
R_T1 + _ǒ3
RT_H RT_C^Ǔ
ǒ_{RTC * RTH}ǓǓ
(1)
R_T2
+
ǒ₂
ǒ_{5 RTH}
RT_C^Ǔ *
RT_C^Ǔ
ǒ_{7 RTH}Ǔ
(2)
For PTC Thermisters:
ǒ₅
R_T1 + _ǒ3
RT_H RT_C^Ǔ
ǒ_{RTH * RTC}ǓǓ
(3)
R_T2
+
ǒ₂
ǒ_{5 RTH}
RT_H^Ǔ *
RT_C^Ǔ
ǒ_{7 RTC}Ǔ
(4)
Where RT_C is the cold temperature resistance and RT_H is the hot temperature resistance of thermistor, as
specified by the thermistor manufacturer.
R_T1 or R_T2 can be omitted If only one temperature (hot or cold) setting is required. Applying a voltage between
the V_TS1 and V_TS2 thresholds to pin TS disables the temperature-sensing feature. Also applying a voltage
between (V_CC – 0.3 V) and Vcc suspends the charge and places the IC in the low-power standby mode.
BATTERY PRE-CONDITIONING
Figure 7 shows the operational flow chart for the bq2420x.
Upon power-up, if the battery voltage is below the V_(LOWV) threshold, the bq2420x applies a pre-charge current,
I_(PRECHG), to the battery. This feature revives deeply discharged cells. The bq2420x activates a safety timer,
t_(PRECHG), during the conditioning phase. If V_(LOWV) threshold is not reached within the timer period, the bq2420x
turns off the charger and enunciates FAULT on the STAT pin. In the case of a FAULT condition, the bq2420x
reduces the current to I(_DETECT). I_(DETECT) is used to detect a battery replacement condition. Fault condition is
cleared by POR or battery replacement.
BATTERY CHARGE CURRENT
Following a successful pre-conditioning, the bq2420x relies on an external current-limited supply to limit the
charge current to the cell. The bq2420x continues this phase until the battery reaches the voltage regulation
phase.
During this phase (and all other phases of operation) in order to protect the integrated powerFET, the internal
short circuit and thermal protection circuits are active.
BATTERY VOLTAGE REGULATION
The voltage regulation feedback is through the BAT pin. This input is tied directly to the positive side of the
battery pack. The bq2420x monitors the battery-pack voltage between the BAT and VSS pins. The bq2420x is
offered in two fixed-voltage versions: 4.1 V and 4.2 V.
As a safety backup, the bq2420x also monitors the charge time in the voltage regulation mode. If taper current is
not detected within this time period, t_(CHG), the bq2420x turns off the charger and enunciates FAULT on the STAT
pin. Fault condition is cleared by POR or battery replacement. Note that the safety timer is reset if the bq2420x is
forced out of the voltage regulation mode.
CHARGE TERMINATION AND RECHARGE
The bq2420x monitors the charging current during the voltage regulation phase. Once the taper threshold,
I_(TAPER), is detected the bq2420x initiates the taper timer, t_(TAPER). Charge is terminated after the timer expires.
The bq2420x resets the taper timer in the event that the charge current returns above the taper threshold,
I_(TAPER).
In addition to the taper current detection, the bq2420x terminates charge in the event that the charge current falls
below the I_(TERM) threshold. This feature allows for quick recognition of a battery removal condition.
Copyright © 2001–2008, Texas Instruments Incorporated
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Product Folder Link(s): bq24200, bq24201 bq24202, bq24203 bq24204, bq24205