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Operating Modes
2.4.5 SLEEP Mode
SLEEP mode is entered automatically if the feature is enabled (
OpConfig [SLEEP]
= 1) and
AverageCurrent()
is below the programmable level
Sleep Current
(default = 10 mA). Once entry into
SLEEP mode has been qualified, but prior to entering it, the fuel gauge performs an ADC autocalibration
to minimize the offset.
During SLEEP mode, the fuel gauge remains in a very-low-power idle state and automatically wakes up
briefly every 20 seconds to take data measurements.
After taking the measurements on the 20-second interval, the fuel gauge will exit SLEEP mode when
AverageCurrent()
rises above
Sleep Current
(default = 10 mA). Alternatively, an early wake-up before the
20-second internal is possible if the instantaneous current detected by an internal hardware comparator is
above an approximate threshold of ±30 mA.
2.4.6 HIBERNATE Mode
HIBERNATE mode could be used when the system equipment needs to enter a very-low-power state, and
minimal gauge power consumption is required. This mode is ideal when system equipment is set to its
own HIBERNATE, SHUTDOWN, or OFF mode.
Before the fuel gauge can enter HIBERNATE mode, the system must use the
SET_HIBERNATE
subcommand to set the
[HIBERNATE]
bit of the
CONTROL_STATUS
register. The fuel gauge waits to
enter HIBERNATE mode until it has taken a valid OCV measurement and the magnitude of the average
cell current has fallen below
Hibernate Current
. The fuel gauge can also enter HIBERNATE mode if the
cell voltage falls below the
Hibernate Voltage
. The fuel gauge will remain in HIBERNATE mode until the
system issues a direct I
2
C command to the fuel gauge. I
2
C communication that is not directed to the fuel
gauge will only briefly wake it up and the fuel gauge immediately returns to HIBERNATE mode.
It is the responsibility of the system to wake the fuel gauge after it has gone into HIBERNATE mode and
to prevent a charger from charging the battery before the
Flags() [OCVTAKEN]
bit is set which signals an
initial OCV reading has been taken. For maximum initialization accuracy, any significant charge or
discharge current should be postponed until the
CONTROL_STATUS [INITCOMP]
bit is set. This could
take up to 10 seconds. After waking, the fuel gauge can proceed with the initialization of the battery
information. During HIBERNATE mode, RAM-based data values are maintained, but gauging status is
lost. Upon exit from HIBERNATE mode, the fuel gauge will immediately reacquire measurements and
reinitialize all gauging predictions.
10
Functional Description
SLUUAC9A – December 2013 – Revised May 2015
Copyright © 2013–2015, Texas Instruments Incorporated