Real-Time Clock with I2C or SPI Interface, Crystal Temperature Compensation, Battery Switchover and Trickle Charger
The EM3027 is an Ultra Low Power CMOS real-time clock IC with two serial interface modes: I2C or SPI. The interface mode is selected by the chip version (see §12). The basic clock is obtained from the 32.768 kHz crystal oscillator. A thermal compensation of the frequency is based on the temperature measurement and calculation of the correction value. The temperature can be measured internally or be input by an external application to the register.
The chip provides clock and calendar information in BCD format with alarm possibility. The actual contents are latched at the beginning of a read transmission and afterwards data are read without clock counter data corruption.
An integrated 16-bit timer can run in Zero-Stop or Auto-Reload mode.
An interrupt request signal can be provided through INT and/or IRQ/CLKOUT pins generated from alarm, timer, voltage detector and Self-Recovery system.
An integrated trickle charger allows recharging backup supply VBack from the main supply voltage VCC through internal resistor(s). The internal device supply will switchover to VCC when VCC is higher than VBack and vice versa.
The device operates over a wide 1.4 to 5.5V supply range and requires only 900 nA at 5V. It can detect internally two supply voltage levels.