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 can be generated by a separate DC/DC converter in the system. The REGOUT LDO output voltage can be programmed to 1.8 V, 2.5 V, 3.0 V, 3.3 V, or 5.0 V, and it can provide an output current of up to 20 mA if thermal conditions permit.

The REGOUT LDO voltage level is selected using the Settings:Configuration:REGOUT Config[REGCTL_2:0] configuration bits as shown below. The LDO is enabled using the Settings:Configuration:REGOUT Config[REG_EN] configuration bit, and its setting can be modified during operation using the 0x69 REGOUT Control() command.

The REGOUT LDO can be programmed to either remain disabled or power up automatically whenever the device exits SHUTDOWN mode, depending on OTP configuration. When the REGOUT LDO is disabled, its output is pulled to VSS with an internal resistance of approximately 2.5-kΩ while the device is in NORMAL mode. If the LDO is configured based on OTP settings to be powered, then at each later power-up the device autonomously loads 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 an ambient temperature of 60°C, a stack voltage of 31.5 V, and LDO programmed to an output voltage of 2.5 V, the device dissipates approximately 580 mW when supplying 20 mA of load current. The package thermal impedance can be used to calculate the resulting die temperature. If this exceeds the device's specified temperature range, the load current must be limited in the system. The BQ77307 REGOUT LDO includes an overtemperature detector, which detects if the die temperature exceeds a level of approximately 120°C and automatically causes the LDO to shutdown, and if the Settings:Configuration:Power Config[OTSD] bit is set, the entire device also enters SHUTDOWN mode.