BQ27546-G1 Datasheet, PDF (9/38 Pages) Texas Instruments – nullSingle-Cell Li-Ion Battery Fuel Gauge

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9 Detailed Description
bq27546-G1
SLUSC53A – MAY 2015 – REVISED DECEMBER 2015
9.1 Overview
The bq27546-G1 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) and time-to-empty (TTE).
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 bq27546-G1 control and status
registers, as well as its data flash locations. Commands are sent from the system to gauge using the bq27546-
G1 serial communications engine, and can be executed during application development, pack manufacture, or
end-equipment operation.
Cell information is stored in the bq27546-G1 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. To access to these locations, use the bq27546-G1 companion evaluation software, individual
commands, or a sequence of data-flash-access commands. To access a desired data flash location, the correct
data flash Subclass and offset must be known. For detailed data flash information, see the bq27546-G1
Technical Reference Manual (SLUUB74).
The bq27546-G1 provides 64 bytes of user-programmable data flash memory, partitioned into two (2) 32-byte
blocks: Manufacturer Info Block A and Manufacturer Info Block B. This data space is accessed through a
data flash interface. For specifics on accessing the data flash, see section Manufacturer Information Blocks in the
bq27546-G1 Technical Reference Manual (SLUUB74).
The key to the bq27546-G1 high-accuracy gas gauging prediction is the Texas Instruments 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 bq27546-G1 measures charge/discharge activity by monitoring the voltage across a small-value series
sense resistor (5 mΩ to 20 mΩ typ.) located between the CELL– and the battery’s PACK– terminal. When a cell
is attached to the bq27546-G1, cell impedance is learned based on cell current, cell open-circuit voltage (OCV),
and cell voltage under loading conditions.
The bq27546-G1 external temperature sensing is optimized with the use of a high accuracy negative
temperature coefficient (NTC) thermistor with R25 = 10 kΩ ± 1% and B25/85 = 3435K ± 1% (such as Semitec
103AT) for measurement. The bq27546-G1 can also be configured to use its internal temperature sensor. The
bq27546-G1 uses temperature to monitor the battery-pack environment, which is used for fuel gauging and cell
protection functionality.
To minimize power consumption, the bq27546-G1 has different power modes: NORMAL, SLEEP, FULLSLEEP,
and HIBERNATE. The bq27546-G1 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 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: italics with brackets[ ]. e.g. [TDA]
Data flash bits: italics, bold, and brackets[ ]. e.g. [LED1]
Modes and states: ALL CAPITALS. e.g. UNSEALED mode
Copyright © 2015, Texas Instruments Incorporated
Product Folder Links: bq27546-G1
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