The LMR436x0-Q1 uses the internal LDO output and the VCC pin for all internal power supply. The VCC pin draws power either from the VIN (in adjustable output variants) or the VOUT/FB (in fixed-output variants). In the fixed output variants, once the LMR436x0-Q1 is active but has yet to regulate, the VCC rail will continue to draw power from the input voltage, VIN, until the VOUT/FB voltage reaches > 3.3 V (or when the device has reached steady-state regulation post the soft start). The VCC rail typically measures 3.3 V in both adjustable and fixed output variants. During start-up, VCC momentarily exceeds the normal operating voltage, then drops to the normal operating voltage.