Real-time clocks are suitable fixed and portable applications

Continuing the trend towards feature integration, Intersil’s micropower ISL12024/25 RTCs are suitable for both fixed and portable applications. This level of integration benefits the customer by reducing design cost and footprint. The ISL12025 also adds a CPU supervisor and watchdog timer for greater BOM reduction.

With on-chip timing and crystal compensation, the devices allow tuning of the crystal frequency through the microcontroller for accurate timekeeping. The ISL12024/25 feature automatic battery backup in the event system power is interrupted and are designed to operate with a wide range of supply voltages from 2.7V to 5.5V and in a battery back-up mode down to 1.8V. Power consumption in either case is quite low, with typical 800nA in battery mode. This further enhances the security and reliability of the final product by extending operation in battery mode.

The ISL12024/25 also provide 4Kbits of EEPROM with eight modes of Block Lock control. Block Lock control allows safe, secure memory for critical user and configuration data by preventing accidental corruption of data. The EEPROM data retention is guaranteed over 2,000,000 write cycles.
The calendar has separate registers for date, month, year and day-of-week. The calendar is correct through 2099, with automatic leap year correction. The 64-bit unique ID is written, verified and locked at the factory, and it is only accessible for reading and cannot be altered by the customer.

The ISL12025 has integrated power-on reset (POR) and watchdog timer functions with five selectable VTRIP levels ranging from a default level of 2.63V to 4.64V, and has a single output for RESETb. The ISL12024 has an IRQb/FOUT pin that is software-selected to provide alarm IRQb or frequency output FOUT . The FOUT has four frequency settings: disabled, 1Hz, 4096Hz and 32,768Hz.

The alarm can be set to any clock/calendar value for a match (for example: every minute, every Tuesday or at 5:23 AM on March 21). The alarm status is available by checking the status register, or the ISL12024 device can be configured to provide an interrupt via the IRQ/FOUT pin. There is a pulse mode for the alarms allowing for repetitive alarm functionality. Offering high reliability, the devices feature a data retention figure of 50 years, and an endurance of 2,000,000 cycles per Byte.

With two non-volatile alarms and a repeat mode (periodic interrupts), other key features of the devices include internal feedback resistor and compensation capacitors, 64-position digitally controlled trim capacitor, six digital frequency adjustment settings to ±30ppm, 512x8-bits of EEPROM, 16-Byte page write mode (32 total pages), single byte write capability, and 400kHz data transfer rate.
Target applications for the devices include utility meters, audio video equipment, modems, network routers, hubs, switches and bridges, cellular infrastructure equipment, fixed broadband wireless equipment, pagers/PDAs, POS equipment, test meters/fixtures, office automation (copiers, fax), computer products, and security-related applications.

The ISL12024 is available now in 8-lead SOIC and TSSOP packages, and the ISL12025 is available now in 8-lead SOIC and TSSOP packages.