PCF8563
NXP Semiconductors
Real-time clock/calendar
14.1 Quartz frequency adjustment
14.1.1 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 pin CLKOUT. The frequency tolerance depends on the quartz
crystal tolerance, the capacitor tolerance and the device-to-device tolerance (on average
5 ppm). Average deviations of 5 minutes per year can be easily achieved.
14.1.2 Method 2: OSCI trimmer
Using the 32.768 kHz signal available after power-on at pin CLKOUT, fast setting of a
trimmer is possible.
14.1.3 Method 3: OSCO output
Direct measurement of OSCO out (accounting for test probe capacitance).
PCF8563
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© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 9 — 16 June 2011
33 of 45
NXP [ NXP ]
