PCF8563_6

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 06 — 21 February 2008

22 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

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).