PCA8802 Datasheet, PDF (1/34 Pages) NXP Semiconductors – ultra low power oscillator with integrated counter for initiating one time password generation

PCA8802
Smartcard RTC; ultra low power oscillator with integrated
counter for initiating one time password generation
Rev. 01 — 19 February 2009
Product data sheet
1. General description
The PCA8802 is a CMOS integrated circuit for battery operation, typically supplied by
button cells or flexible polymer batteries. Incorporated is a 32.768 kHz quartz crystal
oscillator circuit including the two load capacitors. The circuit is optimized for a quartz with
6 pF load capacitance specification. Higher values can also be used with the addition of
external load capacitors.
The main function of the oscillator is to generate a ¹â„₃₂ Hz clock signal which is used to
increment a 24 bit binary counter. The counter can be read over the serial interface and
may also be set to any desired value. Control over the divider chain also allows for
accurate starting of the counter. Incrementing of the counter value during read is
prevented by freezing of the counter during access.
An interrupt signal is also available and is triggered coincident with the counter updating.
This signal may be used as a wake-up for a microcontroller.
2. Features
I 32.768 kHz quartz oscillator, amplitude regulated with excellent frequency stability and
high immunity to leakage currents
I Very low current consumption: typically 130 nA
I Two wire serial interface (I²C-bus)
I Integrated 24 bit counter with auto increment every 32 seconds
I Interrupt output for processor wake-up
I Stop function for accurate time setting and current saving during shelf life
I User test modes for accelerated application testing and development
I Two integrated quartz crystal oscillator capacitors
3. Applications
I One time password function generators
I Ultra low power time keeper circuit