PCF8583
NXP Semiconductors
Clock and calendar with 240 x 8-bit RAM
11. Application information
11.1 Quartz frequency adjustment
11.1.1 Method 1: Fixed OSCI capacitor
By evaluating the average capacitance necessary for the application layout, a fixed
capacitor can be used. The frequency is measured using the 1 Hz signal available after
power-on at the interrupt output (pin 7). The frequency tolerance depends on the quartz
crystal tolerance, the capacitor tolerance and the device-to-device tolerance. Average
deviations of ±5 minutes per year are possible.
11.1.2 Method 2: OSCI trimmer
Using the alarm function (via the I2C-bus) a signal faster than the 1 Hz is generated at the
interrupt output for fast setting of a trimmer.
Procedure:
• Power the device on
• Initialize the device (alarm functions).
Routine:
• Set clock to time t and set alarm to time t + Δt
• at time t + Δt (interrupt) repeat routine.
11.1.3 Method 3: Direct measurement
Direct measurement of oscillator output (allowing for test probe capacitance).
PCF8583
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Product data sheet
Rev. 06 — 6 October 2010
24 of 37
NXP [ NXP ]
