BQ27741-G1_14 Datasheet, PDF (13/39 Pages) Texas Instruments – Single Cell Li-Ion Battery Fuel Gauge with Integrated Protection

bq27741-G1
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SLUSBF2 – JULY 2013
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.
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.
High-Side NFET Charge and Discharge FET Drive
The CHG or DSG FET is turned on by pulling the FET gate input up to V_FETON. The FETs are turned off by
pulling the FET gate input down to V_SS. These FETs are automatically turned off by the protector based on the
detected protection faults, or when commanded to turn off via the FETTest(0x74/0x75) extended command.
Once the protection fault(s) is cleared, the FETs may be turned on again.
Operating Modes
The battery protector has several operating modes:
• Virtual shutdown mode
– Analog shutdown
– Low voltage charging
• UVP fault (POR state)
• Normal mode
• Shutdown wait
• OCD or SCD fault mode
• OCC fault mode
• OVP fault mode
The relationships among these modes are shown in Figure 3.
Copyright © 2013, Texas Instruments Incorporated
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