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BQ2011 Datasheet(PDF) 3 Page - Texas Instruments |
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BQ2011 Datasheet(HTML) 3 Page - Texas Instruments |
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3 / 21 page 
Functional Description General Operation The bq2011 determines battery capacity by monitoring the amount of charge input to or removed from a re- chargeable battery. The bq2011 measures discharge and charge currents, estimates self-discharge, monitors the battery for low-battery voltage thresholds, and compen- sates for temperature and charge/discharge rates. The charge measurement is made by monitoring the voltage across a small-value series sense resistor between the negative battery terminal and ground. The available battery charge is determined by monitoring this voltage over time and correcting the measurement for the envi- ronmental and operating conditions. Figure 1 shows a typical battery pack application of the bq2011 using the LED display with absolute mode as a charge-state indicator. The bq2011 can be configured to display capacity in either a relative or an absolute dis- play mode. The relative display mode uses the last measured discharge capacity of the battery as the bat- tery “full” reference. The absolute display mode uses the programmed full count (PFC) as the full reference, forc- ing each segment of the display to represent a fixed amount of charge. A push-button display feature is available for momentarily enabling the LED display. The bq2011 monitors the charge and discharge currents as a voltage across a sense resistor (see RS in Figure 1). A filter between the negative battery terminal and the SR pin may be required if the rate of change of the bat- tery current is too great. 3 bq2011 FG201101.eps PFC SEG5 SEG4 SEG3 SEG2 SEG1 VSS DISP SB VCC REF bq2011 Gas Gauge IC MODE SR RBI DQ VCC C1 0.1 F Q1 ZVNL110A R1 RS RB1 RB2 Load Charger Indicates optional. Directly connect to VCC across 4 cells (4.8V nominal and should not exceed 6.5V) with a resistor and a Zener diode to limit voltage during charge. Otherwise, R1, C1, and Q1 are needed for regulation of >4 cells. Programming resistors and ESD-protection diodes are not shown. R-C on SR may be required, (application-specific), where the maximum R should not exceed 20K. Figure 1. Battery Pack Application Diagram—LED Display, Absolute Mode |
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