BQ27510_08 Datasheet, PDF (7/36 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Direct Battery Connection

bq27510
www.ti.com.......................................................................................................................................................... SLUS816A – MARCH 2008 – REVISED JUNE 2008
GENERAL DESCRIPTION
The bq27510 accurately predicts the battery capacity and other operational characteristics of a single Li-based
rechargeable cell. It can be interrogated by a system processor to provide cell information, such as
state-of-charge (SOC), time-to-empty (TTE) and time-to-full (TTF).
Information is accessed through a series of commands, called Standard Commands. Further capabilities are
provided by the additional Extended Commands set. Both sets of commands, indicated by the general format
Command( ), are used to read and write information contained within the bq27510 control and status registers,
as well as its data flash locations. Commands are sent from system to gauge using the bq27510’s I²C serial
communications engine, and can be executed during application development, pack manufacture, or
end-equipment operation.
Cell information is stored in the bq27510 in non-volatile flash memory. Many of these data flash locations are
accessible during application development. They cannot, generally, be accessed directly during end-equipment
operation. Access to these locations is achieved by either use of the bq27510’s companion evaluation software,
through individual commands, or through a sequence of data-flash-access commands. To access a desired data
flash location, the correct data flash subclass and offset must be known.
The bq27510 provides 96 bytes of user-programmable data flash memory, partitioned into 3 32-byte blocks:
Manufacturer Info Block A, Manufacturer Info Block B, and Manufacturer Info Block C. This data space is
accessed through a data flash interface. For specifics on accessing the data flash, see section Manufacturer
Information Blocks.
The key to the bq27510’s high-accuracy gas gauging prediction is Texas Instrument’s proprietary Impedance
Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties to create
state-of-charge predictions that can achieve less than 1% error across a wide variety of operating conditions and
over the lifetime of the battery.
The bq27510 measures charge/discharge activity by monitoring the voltage across a small-value series sense
resistor (5 mΩ to 20 mΩ typ.) located between the system’s Vss and the battery’s PACK– terminal. When a cell
is attached to the bq27510, cell impedance is computed, based on cell current, cell open-circuit voltage (OCV),
and cell voltage under loading conditions.
The bq27510 must use a Semitec 103AT NTC thermistor for temperature measurement, or can also be
configured to use its internal temperature sensor. When an external themistor is used, a 18.2k pull up resistor
between BT/TOUT and TS pins is also required. The bq27510 uses temperature to monitor the battery-pack
environment, which is used for fuel gauging and cell protection functionality.
To minimize power consumption, the bq27510 has several power modes: NORMAL, SLEEP, HIBERNATE, and
BAT INSERT CHECK. The bq27510 passes automatically between these modes, depending upon the
occurrence of specific events, though a system processor can initiate some of these modes directly. More details
can be found in Section Power Modes.
NOTE:
FORMATTING CONVENTIONS IN THIS DOCUMENT:
Commands: italics with parentheses and no breaking spaces, e.g.
RemainingCapacity( ).
Data Flash: italics, bold, and breaking spaces, e.g. Design Capacity.
Register bits and flags: brackets and italics, e.g. [TDA]
Data flash bits: brackets, italics and bold, e.g: [LED1]
Modes and states: ALL CAPITALS, e.g. UNSEALED mode.
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): bq27510
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