Datasheet

1. General description
The PCF2127AT
1
is a CMOS
2
Real Time Clock (RTC) and calendar with an integrated
Temperature Compensated Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartz
crystal optimized for very high accuracy and very low power consumption. The
PCF2127AT has 512 bytes of general purpose static RAM, a selectable I
2
C-bus or
SPI-bus, a backup battery switch-over circuit, a programmable watchdog function, a
timestamp function, and many other features.
2. Features and benefits
 Temperature Compensated Crystal Oscillator (TCXO) with integrated capacitors
 Typical accuracy: 3ppm from 15 C to +60 C
 Integration of a 32.768 kHz quartz crystal and oscillator in the same package
 Provides year, month, day, weekday, hours, minutes, seconds, and leap year
correction
 512 bytes of general purpose static RAM
 Timestamp function
 with interrupt capability
 detection of two different events on one multilevel input pin (for example, for tamper
detection)
 Two line bidirectional 400 kHz Fast-mode I
2
C-bus interface (I
OL
= 3 mA at pin
SDA/CE
)
 3 line SPI-bus with separate data input and output (maximum speed 6.5 Mbit/s)
 Battery backup input pin and switch-over circuitry
 Battery backed output voltage
 Battery low detection function
 Extra power fail detection function with input and output pins
 Power-On Reset Override (PORO)
 Oscillator stop detection function
 Interrupt output and system reset pin (open-drain)
 Programmable 1 second or 1 minute interrupt
 Programmable countdown timer with interrupt capability
 Programmable watchdog timer with interrupt and reset capability
 Programmable alarm function with interrupt capability
 Programmable square wave open-drain output pin
PCF2127AT
Integrated RTC, TCXO and quartz crystal
Rev. 6 — 11 July 2013 Product data sheet
1. As well as the PCF2129.
2. The definition of the abbreviations and acronyms used in this data sheet can be found in Section 20
.