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BQ2000PN-B5 Datasheet(PDF) 4 Page - Texas Instruments |
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BQ2000PN-B5 Datasheet(HTML) 4 Page - Texas Instruments |
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4 / 18 page  Initiation and Charge Qualification The bq2000 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 bq2000 charge qualifica- tion is based on battery voltage and temperature. If voltage on pin BAT is less than the internal threshold, VLBAT, the bq2000 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 bq2000 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 bq2000 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 bq2000 detects the battery chemistry by monitoring the battery-voltage profile during the initial stage of the fast charge. If the voltage on BAT input rises to the in- ternal VMCV reference, the IC assumes a Li-Ion battery. Otherwise the bq2000 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. In 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 bq2000 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 bq2000 fast-charges NiCd or NiMH batteries using a current-limited algorithm. Dur- ing the fast-charge period, it monitors charge time, tem- perature, and voltage for adherence to the termination 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 with a trickle maintenance-charge that continues as long as the voltage on pin BAT remains below VMCV. 4 bq2000 GR2000CA.eps IMAX IMIN Trickle VLBAT VMCV Time Phase 1 Phase 2 Fast Charge Voltage Current Figure 3. Lithium-Ion Charge Algorithm |
Similar Part No. - BQ2000PN-B5 |
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Similar Description - BQ2000PN-B5 |
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