1.

General description

The PCF2128 is a ready to run CMOS real time clock/calendar with an integrated

temperature compensated crystal oscillator (TCXO). In timekeeping applications the high

accuracy of the PCF2128 allows it to be used as a replacement for costly and higher

powered long wave receivers or GPS receivers. A programmable battery switch-over

circuit enables an uninterruptible power supply and consequently continuous timekeeping.

The PCF2128 additionally features 512 bytes of general purpose RAM, a programmable

watchdog, a time stamp facility and a voltage monitoring facility. Programming is possible

2.

Features

PCF2128

Integrated RTC / TCXO / Crystal

Rev. 00.03 — 4 June 2007

Preliminary [short] data sheet

Integration of a 32.768 kHz quartz

crystal in the same package as the RTC

512 bytes of general purpose static

RAM

temperature compensated crystal

oscillator (TCXO) with integrated

capacitors.

1 second or 1 minute interrupt output

accuracy:

typically 3 ppm from

−20 °C to +70 °C,

typically 5 ppm from

−40 °C to +85 °C

oscillator stop detection

provides year, month, day, weekday,

hours, minutes and seconds

two line bi-directional 1 MHz fast mode

programmable alarm function with

interrupt capability

timestamp input

programmable countdown timer with

interrupt capability

power-on reset

programmable watchdog timer with

interrupt and reset capability

3 line SPI interface with separate data

input and output (maximum speed

6.5 Mbits/s)

timestamp function with interrupt

capability

programmable square wave output pin

battery backup input pin and switch-over

circuitry

write A2H

extra power fail detection with input and

output pins

clock operating voltage: <tbd> to 5.5 V

battery low detection

low backup current; typical 0.95

μA at

°C

battery backed output voltage pin