SLUUCW9 December 2023 BQ76972
The BQ76972 device integrates a DEEPSLEEP mode, which is a low power mode that allows the REG1 and REG2 LDOs to remain powered, but disables 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 by sending the 0x000F DEEPSLEEP() subcommand twice in a row within a 4-sec time window. The device exits DEEPSLEEP mode and returns to NORMAL mode if the 0x000E EXIT_DEEPSLEEP() subcommand is sent, or if the RST_SHUT pin is asserted for <1 second, or if a charger is attached (which is detected by the voltage on the LD pin rising from below VWAKEONLD to exceed it). In addition, if the BAT pin voltage falls below VPORA–VPORA_HYS, the device transitions to SHUTDOWN mode.
When the device exits DEEPSLEEP mode, it first completes a full measurement loop and evaluates conditions relative to enabled protections, to ensure that conditions are acceptable to proceed to NORMAL mode. This may take ≈250 ms plus the time for the measurement loop to complete.
The REG1 and REG2 LDOs maintain their power state when entering DEEPSLEEP mode if the Settings:Configuration:Power Config[DPSLP_LDO] configuration bit is set. The device also provides the ability to keep the LFO running while in DEEPSLEEP mode, which allows for a faster responsiveness to communications and transition back to NORMAL mode, but consumes additional power. This is controlled by the Settings:Configuration:Power Config[DPSLP_LFO] configuration bit.
Other than the 0x000E EXIT_DEEPSLEEP() subcommand, communications with the device over the serial interface do not cause it to exit DEEPSLEEP mode. However, because no measurements are taken while in DEEPSLEEP mode, there is no new information available for readout. To collect measurement data without powering the system the user can do the following: