The BQ77307 contains an integrated 1.8-V LDO (REG18) that provides a regulated 1.8-V supply voltage for the device's internal circuitry and digital logic. The supply current for this LDO is drawn from the BAT pin.

The device also integrates a programmable LDO (REGOUT) for external circuitry, such as a host processor or external transceiver circuitry. The REGOUT LDO takes its input from the REGSRC pin, which is generally expected to be connected to the top-of-stack, or the REGSRC voltage can be generated by a separate DC/DC converter in the system. The REGOUT LDO can provide an output current of up to 20 mA if thermal conditions permit.

The REGOUT LDO can be programmed to either remain disabled or power up automatically whenever the device exits SHUTDOWN mode, depending on OTP configuration. The LDO output voltage can be programmed to 1.8 V, 2.5 V, 3.0 V, 3.3 V, or 5.0 V by modifying configuration settings. When the REGOUT LDO is disabled and the device is in NORMAL mode, its output is pulled to VSS with an internal resistance of approximately 2.5 kΩ. If the LDO is configured based on OTP settings to be powered, then at each later power-up the device will autonomously load the OTP settings and enable the LDO as configured, without requiring communications first.

The BQ77307 is designed to operate properly with a die temperature up to 110°C, therefore the system design must avoid drawing excessive current from the REGOUT LDO if it could result in the die temperature exceeding this level. For example, with a stack voltage of 22.5 V, and REGOUT programmed to an output voltage of 2.5 V, the device will dissipate approximately 400 mW when supplying 20 mA of load current. The package thermal impedance can be used to calculate the resulting die temperature based on the maximum ambient temperature expected. If this exceeds the device's specified temperature range, the load current may need to be limited in the system.

The BQ77307 includes a die temperature monitor which detects if the die temperature exceeds approximately 120°C. If this occurs, the REGOUT LDO is disabled, and depending on the configuration setting, the device will also enter SHUTDOWN mode. If the REGOUT LDO is disabled due to overtemperature (but the device is not shut down) and the die temperature reduces below the threshold, the REGOUT LDO will automatically power on again.