Each operational amplifier can be configured in different modes, selected by the OPAMP Control x register (OPAMPCTRLx):
After being enabled, a start-up delay is added before the output of the operational amplifier is available. This start-up time is measured internally to account for environmental changes such as temperature or voltage supply level.
When the OPAMP is ready, the respective Ready x bit in the Status register is set (STATUS.READYx=1).
If the supply voltage is below 2.5V, the start-up time is also dependent on the voltage doubler. If the supply voltage is always above 2.5V, the voltage doubler can be disabled by setting the Low-Power Mux bit in the Control A Register (CTRLA.LPMUX).