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BQ2000PW Datasheet(PDF) 6 Page - Texas Instruments |
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BQ2000PW Datasheet(HTML) 6 Page - Texas Instruments |
6 / 29 page BAT+ bq2000 2 4 BAT VSS RB1 RB2 bq2000 SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 www.ti.com Initiation and Charge Qualification The bq2000 initiates a charge cycle when it detects • Application of power to VCC • Battery replacement • Exit from sleep mode • Capacity depletion (Li-Ion only) Immediately following initiation, the IC enters a charge-qualification mode. The bq2000 charge qualification is based on battery voltage and temperature. If the voltage on the BAT pin is less than the internal threshold, VLBAT, the bq2000 enters the battery conditioning state. This condition indicates the possibility 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 Maintenance Charge," the trickle pulse-width is user-selectable and is set by the value of the resistance connected between the RC pin and VSS. During charge qualification, the LED pin blinks at a 1Hz rate, indicating the pending status of the charger. Once battery conditioning (trickle charge) has raised the voltage on the BAT pin above VLBAT, the IC enters fast charge, if the battery temperature is within the VLTF to VHTF range. The BQ2000 will stay in the battery conditioning state indefinitely and will not progress to fast charge until the voltage on the BAT pin is above VLBAT and the temperature is within the VLTF and VHTF range. No timer is implemented during battery conditioning. 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 the BAT pin rises to the internal VMCV reference, the IC assumes a Li-Ion battery. Otherwise, the bq2000 assumes a NiCd/NiMH chemistry. While in the fast charge state, the LED pin is pulled low (the LED is on). As shown in Figure 3, a resistor voltage-divider between the battery pack's positive terminal and VSS scales the battery voltage. A low-pass filter then smooths out this voltage to present a clean signal to the BAT pin. 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. Otherwise, different scaling is required. Figure 3. Battery Voltage Divider and Filter 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 charge qualification (which includes trickle charge, if required ), the bq2000 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 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 the BAT pin remains below VMCV. 6 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 |
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