BQ76952: LDO

Hi Ivy,

These are best explained by the sections in the BQ76952 technical reference manual.  It is a big document, so it can be hard to find the right information quickly.

1. The default state of the registers is off for the BQ76952.  See the settings sections of the technical reference manual, 13.3.2.2 and 13.3.2.3:

Do note however there are 3 part variations offered with the REG1 pre-programmed, see the BQ76952 data sheet section 5 Device Comparison Table: https://www.ti.com/document-viewer/BQ76952/datasheet/GUID-3420A05A-C025-4A9B-B79D-1D4FEE10CD70#TITLE-SLUSCS3T4721029-16 

2. The default state of the LDOs is off when the part is awakened as shown above, unless the settings made by the MCU or factory test system have programmed them into OTP.  If the settings have been programmed into OTP, the regulators will come on to the state selected when the part wakes up to NORMAL operational mode.  See section 7 of the technical reference manual, Operational Modes for a description.  Quickly:

Normal: regulators will stay on based on the configuration

Sleep: regulators will stay on based on the configuration

Deepsleep: regulators will go off by default, but could be configured to stay on, see 13.3.2.1 Settings:Configuration:Power Config if interested.

Shutdown: regulators are off

3.  If the part is sent to Deepsleep mode the regulators will go off or stay on depending on the Settings:Configuration:Power Config[DPSLP_LDO] bit.  When the mode is changed back to Normal the regulators would come on again or stay on.  If the part is sent to Shutdown regulators will go off. When awakened to Normal they will be set according to the configuration in OTP of off by default if OTP was not set.

Yes, it is important to plan for the power control when designing the battery system.  Here are 2 concepts, there are likely more possible:

If the BQ76952 is to provide power to the MCU the OTP should be set appropriately so that when awakened by some circuit it will power the MCU.  The MCU can then make other configuration selections as desired or required for battery operation.  Normally the MCU would not want to turn off the regulators, but could send the BQ76952 to Shutdown if desired to turn off the battery system.

If the MCU operates from a separate regulator such as a DC-DC and will always be on, the designer could choose to send the BQ76952 to Shutdown when not needed.  When the MCU sensed operation was to resume the MCU would wake the BQ76952 and set any configuration needed which was not stored in OTP.