NXP Semiconductors
UM10699
User manual for SPI-bus RTC demoboard OM11059
UM10699
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© NXP B.V. 2013. All rights reserved.
User manual
Rev. 1 — 04 April 2013
4 of 12
3. Hardware set-up
3.1 General requirements for the RTC PCF85063BTL
The RTC circuit just requires one external part: tuning fork quartz as resonator. The
oscillation capacitors are integrated and therefore there is no need for external
capacitors. The quartz crystal must be placed close to the RTC circuit, avoiding long
lines which may pick up noise. Avoid any tracks with high frequency signals (fast edges)
close to the RTC, quartz, or quartz interconnect.
The interface uses a three-line standard SPI protocol: chip enable, serial clock, serial
data I/O operating up to 8 MHz.
Supply voltage: The RTC is specified from 1.8 V to 5.5 V. The RTC, excluding the SPI-
bus interface, is however operating down to a lower voltage. It is recommended to have a
decoupling capacitor on the VDD-VSS rails close by.
Due to the low power consumption of below 1 μW, no precautions for heat dissipations
are required.
CLKOUT can be used to measure the frequency or be used as reference for frequency
generation with a PLL.
Fig 2.
Interfacing to microcontroller