The REGN LDO supplies internal bias circuits as well as the HSFET and LSFET gate drive. The LDO also provides bias rail to TS external resistors. The pull-up rail of STAT can be connected to REGN as well. The REGN is enabled when all the below conditions are valid.

1. VBUS above V_{VBUS_UVLOZ}
2. VBUS above V_BAT + V_SLEEPZ in buck mode or VBUS below V_BAT + V_SLEEP in boost mode
3. After 220 ms delay is completed

If one of the above conditions is not valid, the device is in high impedance mode (HIZ) with REGN LDO off. The device draws less than I_{VBUS_HIZ} from VBUS during HIZ state. The battery powers up the system when the device is in HIZ.