The bq2085-V1P3 SBS-compliant gas gauge IC for
battery pack or in-system installation maintains an
accurate record of available charge in Li-ion or Li-polymer
batteries. The bq2085-V1P3 monitors capacity and other
critical parameters of the battery pack and reports the
information to the system host controller over a serial
communication bus. It is designed to work with the
bq29311 analog front-end (AFE) protection IC to maximize
functionality and safety and minimize component count
and cost in smart battery circuits. Using information from
the bq2085-V1P3, the host controller can manage
remaining battery power to extend the system run time as
much as possible.
The bq2085-V1P3 uses an integrating converter with
continuous sampling for the measurement of battery
charge and discharge currents. Optimized for coulomb
counting in portable applications, the self-calibrating
integrating converter has a resolution better than 3-nVh
and an offset measurement error of less than 1-µV
(typical). For voltage and temperature reporting, the
bq2085-V1P3 uses a 16-bit A-to-D converter. In
conjunction with the bq29311, the onboard ADC also
monitors individual cell voltages in a battery pack and
allows the bq2085-V1P3 to generate the control signals
necessary to implement the cell balancing and the
required safety protection for Li-ion and Li-polymer battery
chemistries.
The bq2085-V1P3 supports the smart battery data
(SBData) commands and charge-control functions. It
communicates data using the System Management Bus
(SMBus) 2-wire protocol. The data available include the
battery’s remaining capacity, temperature, voltage,
current, and remaining run-time predictions. The
bq2085-V1P3 provides LED drivers and a push-button
input to depict remaining battery capacity from full to empty
in 20%, 25%, or 33% increments with a 3-, 4-, or
5-segment display.
The bq2085-V1P3 contains 512 bytes of internal data
flash memory, which store configuration information. The
information includes nominal capacity and voltage,
self-discharge rate, rate compensation factors, and other
programmable cell-modeling factors used to accurately
adjust remaining capacity for use-conditions based on
time, rate, and temperature. The bq2085-V1P3 also
automatically calibrates or learns the true battery capacity
in the course of a discharge cycle from programmable near
full to near empty levels.
The bq29311 AFE protection IC provides power to the
bq2085-V1P3 from a 3 or 4 series Li-ion cell stack,
eliminating the need for an external regulator circuit.
