PCF8593P datasheet(23/35 Pages) NXP

23 / 35 page

PCF8593

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Product data sheet

Rev. 04 — 6 October 2010

23 of 35

NXP Semiconductors

PCF8593

Low power clock and calendar

11. Application information

11.1 Oscillator 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 best measured via the 1 Hz signal which can be

programmed to occur at the interrupt output (pin 7). 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 achieved.

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

• Apply RESET.

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).

PCF8593P Datasheet(PDF) 23 Page - NXP Semiconductors