NXP Semiconductors PCF85x3, PCF2123, PCA8565, PCA2125 user manual Features

NXP Semiconductors	UM10301
	User Manual PCF85x3, PCA8565 and PCF2123, PCA2125

2. Features

The NXP real-time clock portfolio includes types for low power, types for automotive and other high temperature applications and applications that need additional RAM. A third family of highly accurate temperature compensated real time clocks will be dealt with in a separate application note. Designed for a range of demanding applications, these real- time clocks/calendars are driven by a low-power 32.768 kHz quartz oscillator, use the SPI or I2C-bus for serial data transfer, and typically consume less than 1 μW of power.

Key features

•Oscillator requires 32.768 kHz external quartz crystal

•Resolution: seconds, minutes, hours, weekday, day, month, and year in 12- or 24-

hour (military) format. All time and alarm registers are in BCD format. Two types include a 1/10th and 1/100th second resolution register

•Clock operating voltage: 1.0 V to 5.5 V or wider, see Table 2

•Low backup current: Ranging from 100 nA to 2 μA at VDD = 1 V and Tamb = 25 °C

•Three line SPI with separate I/O or I2C serial interface

•Freely programmable timer and alarm functions, each with interrupt capability

•Freely programmable Watchdog timer

•Programmable clock output for peripheral devices: 32.768 kHz, 1024 Hz, 32 Hz and 1 Hz (not all types)

•One or two integrated oscillator capacitors (connected to the output of amplifier OSCO in case of only one integrated capacitor)

•Internal power-on reset

•Open-drain interrupt pin

•Wide variety of packages available including naked die

Addresses and data are transferred serially via an SPI bus with a maximum speed of 7.0 Mbps (PCF2123, PCA2125) or via a two-line, bidirectional I2C-bus that operates at a maximum speed of 400 kbps (Fast-Mode, PCF8563 and PCA8565) or 100 kbps (Standard-Mode, PCF8583 and PCF8593). The built-in word address register is incremented automatically after each data byte is written or read.

With the PCF8583, the address pin A0 is used to program the software address, so that two devices can be connected to the same I2C-bus without additional hardware.

Each RTC has an internal power-on reset and a programmable clock output with open drain configuration to drive peripheral devices. A low voltage detector (not included on the PCF8583,93 and PCA2125) warns if the integrity of all clock functions is no longer guaranteed.

Power consumption is kept to a minimum in all the devices. The PCF2123 and PCF8563, optimized for battery-powered applications, consume as little as 100 nA at 2V and 250 nA at 1V respectively. With careful selection of the crystal used, the PCF2123 consumes less than 100 nA on a 1.5 V supply.

The seconds, minutes, hours, days, weekdays, months, years as well as the minute alarm, hour alarm, day alarm and weekday alarm registers are all coded in Binary Coded Decimal (BCD) format. This format is popular with RTCs for the reason that time and date in BCD format can easily be displayed in human-readable style without conversion.

UM10301_1		© NXP B.V. 2008. All rights reserved.
User manual	Rev. 01 — 23 December 2008	4 of 52