BQ27742-G1 Datasheet, PDF (19/46 Pages) Texas Instruments – Single-Cell Li-Ion Battery Fuel Gauge with Programmable Hardware Protection

www.ti.com
bq27742-G1
SLUSBV9C – MARCH 2014 – REVISED FEBRUARY 2016
Feature Description (continued)
7.3.3.3 FULLSLEEP Mode
FULLSLEEP mode turns off the high-frequency oscillator and performs AverageCurrent(), Voltage(), and
Temperature() less frequently which results in power consumption that is lower than that of the SLEEP mode.
FULLSLEEP mode can be enabled by two methods:
• Setting the [FULLSLEEP] bit in the Control Status register using the FULL_SLEEP subcommand and Full
Sleep Wait Time (FS Wait) in data flash is set as 0.
• Setting the Full Sleep Wait Time (FS Wait) in data flash to a number larger than 0. This method is disabled
when the FS Wait is set as 0.
FULLSLEEP mode is entered automatically when it is enabled by one of the methods above. When the first
method is used, the gauge enters the FULLSLEEP mode when the fuel gauge is in SLEEP mode. When the
second method is used, the FULLSLEEP mode is entered when the fuel gauge is in SLEEP mode and the timer
counts down to 0.
The fuel gauge exits the FULLSLEEP mode when there is any communication activity. Therefore, the execution
of SET_FULLSLEEP sets the [FULLSLEEP] bit. The FULLSLEEP mode can be verified by measuring the
current consumption of the gauge.
During FULLSLEEP mode, the fuel gauge periodically takes data measurements and updates its data set.
However, a majority of its time is spent in an idle condition.
The fuel gauge exits SLEEP if any entry condition is broken, specifically when either:
• AverageCurrent() rises above Sleep Current, or
• A current in excess of I_WAKE through R_SENSE is detected.
While in FULLSLEEP mode, the fuel gauge can suspend serial communications by as much as 4 ms by holding
the comm line(s) low. This delay is necessary to correctly process host communication, because the fuel gauge
processor is mostly halted in SLEEP mode.
7.3.4 Li-Ion Battery Protector Description
The battery protector controls two external high-side N-channel FETs in a back-to-back configuration for battery
protection. The protector uses two voltage doublers to drive the CHG and DSG FETs on.
7.3.4.1 High-Side NFET Charge and Discharge FET Drive
These FETs are automatically turned off by the protector based on the detected hardware protection faults or by
the fuel gauge based on detected firmware protection faults. This enables the gauge to be configured with
effectively two levels of safety: the first level employing conservative protection settings to keep the cell within a
safe operating area and the second level set to act as a fail-safe measure to prevent cell damage. Once the
protection fault(s) is deemed to be cleared, the protector or fuel gauge will re-enable the applicable FET(s).
Additionally, the FET drivers can be manually tested at production using the FETTest(0x74/0x75) extended
command if needed.
7.3.4.2 Protector Configuration
The integrated Li-Ion hardware protector includes full programmability of its fault detection thresholds, eliminating
the need to order several part variants to accommodate different system safety threshold needs. Configuration of
the thresholds is provided in the form of data flash parameters, Prot OV Config and Prot OC Config, which are
bit-mapped to two simple lookup tables that determine the protector safety thresholds. Table 3 through Table 6
detail the protection settings available for hardware overvoltage, overcurrent in charge, overcurrent in discharge,
and short-circuit in discharge, respectively. An added degree of flexibility is made possible in combining the
programmable thresholds with changes to the selected sense resistor value, enabling a wide variety of Li-Ion
protection options in a single device.
Copyright © 2014–2016, Texas Instruments Incorporated
Product Folder Links: bq27742-G1
Submit Documentation Feedback
19