BQ27620-G1 Datasheet, PDF (9/45 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

bq27620-G1
www.ti.com
SLUSAE3 – OCTOBER 2012
4 GENERAL DESCRIPTION
The bq27620-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 time-to-empty (TTE), time-to-full (TTF) and state-of-charge (SOC) as well as SOC interrupt signal to the
host.
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 device control and status
registers, as well as its data flash locations. Commands are sent from system to gauge using the
bq27620-G1’s I²C serial communications engine, and can be executed during application development,
system manufacture, or end-equipment operation.
Cell information is stored in the device 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 bq27620-G1’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 bq27620-G1 provides a 32-byte user-programmable data flash Manufacturer Info Block. This data
space is accessed through a data flash interface. For specifics on accessing the data flash,
MANUFACTURER INFORMATION BLOCKS.
The key to the bq27620-G1’s high-accuracy gas gauging prediction is Texas Instrument’s proprietary
Impedance Track™ algorithm with Dynamic Voltage Correlation (IT-DVC). This algorithm uses cell
measurements, characteristics, and properties to create state-of-charge predictions that can achieve less
than 5% error across a wide variety of operating conditions and over the lifetime of the battery.
The device utilizes a comprehensive battery model to estimate the average current in real time,
eliminating the need of a sense resistor. When a cell is attached to the device, cell impedance is
computed, open-circuit voltage (OCV), and cell voltage under loading conditions.
The device external temperature sensing is optimized with the use of a high accuracy negative
temperature coefficient (NTC) thermistor with R25 = 10.0kΩ ±1%. B25/85 = 3435K ± 1% (such as Semitec
NTC 103AT). The bq27620-G1 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
bq27620-G1 uses temperature to monitor the battery-pack environment, which is used for fuel gauging
and cell protection functionality.
To minimize power consumption, the device has different power modes: NORMAL, SLEEP, HIBERNATE,
and BAT INSERT CHECK. The bq27620-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: 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 © 2012, Texas Instruments Incorporated
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GENERAL DESCRIPTION
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