35.3.2.7 Enable and Disable

An op amp can be configured to be in one of three possible Enable/Disable modes:
  • Enabled/disabled by software with all events disabled (SW_ENABLED_WITHOUT_EVENTS mode)
  • Enabled/disabled by the event system (EVENT_ENABLED mode)
  • Enabled/disabled by software with other events enabled (SW_ENABLED_WITH_EVENTS mode)

To select SW_ENABLED_WITHOUT_EVENTS mode, a ‘0’ must be written to the EVENTEN bit in OPnCTRLA. In SW_ENABLED_WITHOUT_EVENTS mode, an op amp is enabled by writing ‘1’ to the ALWAYSON bit in OPnCTRLA. The op amp stays enabled as long as the ALWAYSON bit is ‘1’. Writing a ‘0’ to the ALWAYSON bit in OPnCTRLA will disable the op amp. The op amp will not respond to incoming events and will not generate events.

To select EVENT_ENABLED mode, the ALWAYSON bit in OPnCTRLA must be written to ‘0’, and the EVENTEN bit must be written to ‘1’. In this mode, the op amp is enabled by the ENABLEn event, and it is disabled by the DISABLEn event. In EVENT_ENABLED mode, the op amp will issue a READYn event when settling is complete. The op amp will also respond to incoming DUMPn and DRIVEn events. Special cases are handled as follows:
  • If an ENABLEn event is received while the op amp is in the process of starting up as a result of a prior ENABLEn event, the most recent ENABLEn event will be ignored, and the READYn event will be issued when the settling time from the first ENABLEn event has elapsed
  • If an ENABLEn event is received while the op amp is already enabled and has completed settling, the op amp will stay enabled with no change in state. The READYn event will also be generated immediately after the ENABLEn event in this case.
  • If a DISABLEn event is received while the op amp is already disabled, the DISABLEn event is ignored, and the op amp remains disabled
  • If both an ENABLEn and DISABLEn event are received simultaneously, the DISABLEn event is ignored, and the ENABLEn event is handled as described in the cases above

To select SW_ENABLED_WITH_EVENTS mode, a ‘1’ must be written to the EVENTEN bit in OPnCTRLA. In SW_ENABLED_WITH_EVENTS mode, an op amp is enabled by writing ‘1’ to the ALWAYSON bit in OPnCTRLA. The op amp stays enabled as long as the ALWAYSON bit is ‘1’. While the op amp is enabled, it will respond to incoming DUMPn and DRIVEn events but will be unaffected by incoming ENABLEn and DISABLEn events. Writing a ‘0’ to the ALWAYSON bit in OPnCTRLA will disable the op amp.