Use of an external oscillator on Sterling LWB

The Sterling-LWB uses a secondary low-frequency sleep clock for low-power mode timing. Either the internal low-precision (LPO) or an external 32.768 kHz precision oscillator is required. The internal LPO frequency range is approximately 33 kHz ± 30% over process, voltage, and temperature, which is adequate for some applications. However, one trade-off caused by this, wide LPO tolerance is a small current consumption increase during power save mode that is incurred by the need to wake up earlier to avoid missing beacons. The Sterling-LWB will auto-detect the LPO clock. If it senses a clock on Pin 19 (32KHZ_OSC_IN), it will use that clock. If it doesn't sense a clock, it will use its own internal LPO. To use the internal LPO: Tie For Pin 19 (32KHZ_OSC_IN) to ground. Do not leave this pin floating. Whenever possible, the preferred approach is to use a precision external 32.768 kHz clock.

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