bq2012

The bq2012 Gas Gauge IC is intended for battery-pack or in-system installation to maintain an accurate record of available battery charge. The IC monitors a voltage drop across a sense resistor connected in series between the negative battery terminal and ground to determine charge and discharge activity of the battery.


Self-discharge of NiMH and NiCd batteries is estimated based on an internal timer and temperature sensor. Compensations for battery temperature of bq2012 and rate of charge or discharge are applied to the charge,discharge, and self-discharge calculations to provide available charge information across a wide range of operating conditions. Battery capacity is automatically recalibrated, or "learned," in the course of a discharg ecycle from full toempty.


The bq2012 includes a charge control output that, when used with other full-charge safety termination methods, can provide a cost-effectivemeans of controlling charge based onthebattery'schargestate.


Nominal available charge of bq2012 may be directly indicated using a five- or six-segment LED display. These segments are used to graphically indi-catenominalavailablecharge.


The bq2012 supports a simple single-line bidirectional serial link to an external processor (common ground). The bq2012 outputs battery information in response to external commandsovertheseriallink.


Internal registers of bq2012 include available charge, temperature, capacity, battery ID, battery status, and programming pin settings. To support subassembly testing, the outputs may also be controlled. The external processor may also overwrite some of the bq2012 gas gaugedataregisters.


The bq2012 may operate directly from three or four cells. With the REF output and an external transistor, a simple, inexpensive regulator can be built to provide V_CC across a greaternumberofcells.