Data Sheet

PCF8563_5 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 05 — 17 July 2007 21 of 32
NXP Semiconductors
PCF8563
Real time clock/calendar
12.1 Quartz frequency adjustment
12.1.1 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 × 10
−6
). Average deviations of ±5 minutes per year can be easily achieved.
12.1.2 Method 2: OSCI trimmer
Using the 32.768 kHz signal available after power-on at pin CLKOUT, fast setting of a
trimmer is possible.
12.1.3 Method 3: OSCO output
Direct measurement of OSCO out (accounting for test probe capacitance).