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BQ2000T Datasheet(PDF) 4 Page - Texas Instruments

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Part No. BQ2000T
Description  Programmable Multi-Chemistry Fast-Charge Management IC
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Maker  TI [Texas Instruments]
Homepage  http://www.ti.com
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BQ2000T Datasheet(HTML) 4 Page - Texas Instruments

 
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Initiation and Charge Qualification
The bq2000T initiates a charge cycle when it detects
n Application of power to VCC
n Battery replacement
n Exit from sleep mode
n Capacity depletion (Li-Ion only)
Immediately following initiation, the IC enters a
charge-qualification mode. The bq2000T charge qualifi-
cation is based on battery voltage and temperature. If
voltage on pin BAT is less than the internal threshold,
VLBAT, the bq2000T enters the charge-pending state.
This condition indicates the possiblility of a defective or
shorted battery pack. In an attempt to revive a fully
depleted pack, the bq2000T enables the MOD pin to
trickle-charge at a rate of once every 1.0s. As explained
in the section “Top-Off and Pulse-Trickle Charge,” the
trickle pulse-width is user-selectable and is set by the
value of the resistance connected to pin RC.
During this period, the LED pin blinks at a 1Hz rate,
indicating the pending status of the charger.
Similarly, the bq2000T suspends fast charge if the battery
temperature is outside the VLTF to VHTF range. (See Table
4.) For safety reasons, however, it disables the pulse
trickle, in the case of a battery over-temperature condition
(i.e., VTS <VHTF). Fast charge begins when the battery
temperature and voltage are valid.
Battery Chemistry
The bq2000T detects the battery chemistry by monitor-
ing the battery-voltage profile during fast charge. If the
voltage on BAT input rises to the internal VMCV refer-
ence, the IC assumes a Li-Ion battery. Otherwise the
bq2000T assumes NiCd/NiMH chemistry.
As shown in Figure 6, a resistor voltage-divider between
the battery pack’s positive terminal and VSS scales the
battery voltage measured at pin BAT. I n a
mixed-chemistry design, a common voltage-divider is
used as long as the maximum charge voltage of the
nickel-based pack is below that of the Li-Ion pack. Oth-
erwise, different scaling is required.
Once the chemistry is determined, the bq2000T
completes the fast charge with the appropriate charge
algorithm (Table 1). The user can customize the
algorithm by programming the device using an external
resistor and a capacitor connected to the RC pin, as
discussed in later sections.
NiCd and NiMH Batteries
Following qualification, the bq2000T fast-charges NiCd
or NiMH batteries using a current-limited algorithm.
During the fast-charge period, it monitors charge time,
temperature, and voltage for adherence to the termina-
tion criteria. This monitoring is further explained in
later sections. Following fast charge, the battery is
topped off, if top-off is selected. The charging cycle ends
4
bq2000T
GR2000CA.eps
IMAX
IMIN
Trickle
VLBAT
VMCV
Time
Phase 1
Phase 2
Fast
Charge
Voltage
Current
Figure 3. Lithium-Ion Charge Algorithm


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