Evaluating Internal RC Oscillator Drift during Deep Power Down
Evaluating internal RC drift requires mapping temperature and voltage sags to expanded radio receive windows that drain battery reserves.
LFXO
Meaning
Low power crystal oscillators generate precise timing signals using a external low frequency quartz crystal. Operating the lfxo provides the highly accurate timing required for maintaining synchronized communication channels in wireless protocols like Bluetooth Low Energy. This component operates with a very low power budget compared to high frequency system clocks.
Clock Precision
Communication schedules rely on tight synchronization to ensure that transmitter and receiver wake up at the exact same instant. Utilizing the lfxo ensures that the time tracking error remains below a few parts per million across the operating temperature range. This accuracy prevents packet loss and minimizes the duration of active radio listening windows.
It represents the primary choice for devices that must run for years on a single coin cell.
Power Consumption
Current draw is kept to a minimum by optimizing the drive strength of the oscillator circuit. While the lfxo requires more power than an integrated RC oscillator, it draws less than one microampere during operation. This trade off is acceptable for devices that need both long battery life and accurate timing.
Startup Behavior
Crystal startup times are relatively long due to the high quality factor of quartz resonators. The system must account for a startup delay of several hundred milliseconds when activating the lfxo.