ZHCSMR2B December 2020 – December 2021 BQ76942
The BQ76942 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 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 a subcommand over the serial communications interface. The device exits DEEPSLEEP mode returns to NORMAL mode if directed by a subcommand, or if the RST_SHUT pin is asserted for < 1-s, 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 based on the configuration setting. The device also provides the ability to keep the LFO running while in DEEPSLEEP mode, which enables a faster responsiveness to communications and transition back to NORMAL mode, but consumes additional power.
Other than sending a subcommand to exit DEEPSLEEP mode, communications with the device over the serial interface do not cause it to exit DEEPSLEEP mode; however, since no measurements are taken while in DEEPSLEEP mode, there is no new information available for readout.