When the voltage at the VIN pin is above the undervoltage lockout (UVLO) rising threshold (typically 1.7 V) and the EN pin is pulled to logic high voltage, the TPS61094 is enabled and starts ramping up the output voltage.

At Auto boost mode, the TPS61094 starts charging the output capacitor with a 300-mA constant current through the bypass switch when the output voltage is below 0.5 V. When the output voltages is charged above 0.5 V, the output current is changed to have output current capability to drive the 3.6-Ω resistance load until the output voltage reaches close to input voltage. After the output voltage reaches close to the input voltage, the TPS61094 starts to detect the configuration conditions of the VCHG, ICHG, and OSEL pins, then latches the configuration. According to the configurations and setup, the TPS61094 enters Boost mode or Buck mode. When input voltage is less than the output voltage setting, the TPS61094 enters Boost mode soft start. The TPS61094 starts switching and output ramps up further. The soft-start time in Boost mode varies with the different output capacitance, load condition, and configuration conditions. When input voltage is higher than the output voltage setting adding 100 mV, the TPS61094 enters Buck mode soft start. The charging current can increase slowly.

The start-up of Forced buck mode is similar to Buck mode in Auto boost mode except the TPS61094 enters Buck mode after the output voltage is close to the input voltage and does not need to have the input voltage higher than the output voltage setting adding 100 mV.

At Forced bypass mode, there is no soft start. The bypass switch is always on and the output is connected to the input directly.

When the voltage at the EN pin is below 0.2 V and MODE is higher than 0.58 V at output voltage higher than 1.8 V, the internal enable comparator turns the device into True shutdown mode. In True shutdown mode, the device is entirely turned off. The output is disconnected from the VIN and SUP pin power supply.