Torwards
AT8563
5 Application Reference
Fig 19 Typical Application diagram
5.1 Crystal frequency adjustment
Method 1: Fixed OSCI capacitor — By evaluating the average capacitance
necessary for the application layout a fixed capacitor can be used. The frequency is
best measured via the 32.768 kHz signal available after power-on at the CLKOUT
pin. The frequency tolerance depends on the quartz crystal tolerance, the capacitor
tolerance and the device-to-device tolerance (on average ±5 × 10−6).
Average deviations of ±5 minutes per year can be easily achieved.
Method 2: OSCI trimmer — The oscillator is tuned to the required accuracy by
adjusting a trimmer capacitor on pin OSCI and measuring the 32.768 kHz signal
available after power-on at the CLKOUT pin.
Method 3: OSCO output — Direct output measurement on pin OSCO (accounting for
test probe capacitance).
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