User manual for the I2C-bus RTC PCF85263A demo board OM13510
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2016. All rights reserved.
Fig 1. Block diagram of PCF85263A
3. Hardware set-up
3.1 General requirement for the RTC PCF85263A
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 I
2
C-bus interface works up to 400 kHz. Supply voltage: 1.8 V to 5.5 V. The RTC,
excluding the I
2
C-bus interface, is however operating down to a lower voltage. It is
recommended to have a decoupling capacitor of 100 nF on the V
DD
-V
SS
rails close by.
Due to the low power consumption of below 1 μW, no precautions for heat dissipations
are required, even in sealed housing environment.
Frequencies of 1 Hz to 32.768 kHz at CLKOUT can be used to measure the frequency
for calibration and/or be used for general purpose e.g. as reference for frequency
generation with a PLL.
