NXP Semiconductors UM10301 PCF2123 - Manual (Page 4)

NXP Semiconductors
UM10301
User Manual PCF85x3, PCA8565 and PCF2123, PCA2125
UM10301_1 © NXP B.V. 2008. All rights reserved.
User manual Rev. 01 — 23 December 2008 4 of 52
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 I
2 C-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 1/10
th
and 1/100
th
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 V
DD
= 1 V and T
amb
= 25 °C
• Three line SPI with separate I/O or I 2
C 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 I
2
C-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 I
2
C-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.