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7.8.3 SLEEP Mode
SLEEP mode is a reduced functionality state that can be optionally used to reduce power dissipation when there
is little or no system load current or charging in progress, but still provides voltage at the battery pack terminals
to keep the system alive. At initial power up, the configuration setting determines whether the device can enter
SLEEP mode. After initialization, SLEEP mode can be allowed or disallowed using subcommands. The device
includes a status bit available via command which indicates whether the device is presently in SLEEP mode or
not.
When the magnitude of the current measurement falls below a programmable current threshold, the system
is considered in relax mode, and the device will autonomously transition into SLEEP mode, if settings
permit. During SLEEP mode, comparator-based protections operate the same as during NORMAL mode.
Measurements of current, voltage, and temperature are taken using the ADC and coulomb counter at
programmable intervals.
The device will exit SLEEP mode if a protection fault occurs, or current begins flowing, or via subcommand.
The current is checked approximately every 2.44 ms and, if it exceeds a programmable level in magnitude, the
device transitions back to NORMAL mode.
The device also includes a 10-second hysteresis on the SLEEP mode entrance, in order to avoid the device
quickly entering and exiting SLEEP mode based on a dynamic load. After transitioning from SLEEP mode
to NORMAL mode, the device will not enter SLEEP mode again for 10-seconds unless overridden via
subcommand. For more details, see the
7.8.4 DEEPSLEEP Mode
The BQ76907 integrates a DEEPSLEEP mode, which is a low power mode that allows the REGOUT LDO to
remain powered, but disables most other subsystems. In this mode, the protection FETs are all disabled, so
no voltage is provided at the battery pack terminals. All protections are disabled, and all voltage, current, and
temperature measurements are disabled.
DEEPSLEEP mode can be entered via subcommand sent by the host. The device will exit DEEPSLEEP mode
and return to NORMAL mode if directed via subcommand or upon a rising edge on the TS or VC0 pins. In
addition, if the BAT pin voltage falls below V
transition to SHUTDOWN mode.
When the device exits DEEPSLEEP mode and returns to NORMAL mode, it first completes a startup
measurement loop and evaluates conditions relative to enabled protections, to ensure that conditions are
acceptable to proceed. This may take approximately 8 ms plus the time for the measurement loop to complete.
The REGOUT LDO will maintain its power state when entering DEEPSLEEP mode. The LFO may be disabled
during DEEPSLEEP mode based on setting. If disabled, it is wakened by I
in a longer than normal clock stretch before the device responds to communications.
7.8.5 SHUTDOWN Mode
SHUTDOWN mode is the lowest power mode of the BQ76907, which can be used for shipping or long-term
storage. In this mode, the device loses all register state information, the internal logic is powered down,
the protection FETs are all disabled, so no voltage is provided at the battery pack terminals. All protections
are disabled, all voltage, current, and temperature measurements are disabled, and no communications are
supported. When the device exits SHUTDOWN, it will read parameters stored in OTP (which is programmed by
TI), which effectively sets the default values for settings. After device powerup, settings can then be changed by
the host writing device registers.
The device can enter SHUTDOWN mode when directed by the host via subcommand. It can also be configured
to enter SHUTDOWN mode automatically based on the top of stack voltage or the minimum cell voltage. The
shutdown based on cell voltage does not apply to cell input pins not used for actual cells.
While the BQ76907 is in NORMAL mode or SLEEP mode, the device can also be configured to enter
SHUTDOWN mode if the internal temperature measurement exceeds a programmable threshold.
Copyright © 2023 Texas Instruments Incorporated
BQ76907 Technical Reference
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PORA
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Manual.
while in DEEPSLEEP mode, the device will
2
C communications, which may result
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