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Real-time clocks enhance security, reduce BOM

Posted: 28 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:real-time clock? clock? calendar? alarm? Intersil?

Real-time clocks from Intersil

Intersil Corp. has introduced the ISL12024 and ISL12025 micropower real-time clock/calendar devices. These devices feature an integrated factory-set 64-bit unique ID that is read-only and tamper-proof for increased security and reduced footprint and BOM cost.

The ISL12024/25 continue the trend toward feature integration by combining clock/calendar/alarm functions with 4Kbits of EEPROM memory and 64bits of unique ID and the ISL12025 also adds a CPU supervisor function, all in a tiny 8-lead package suitable for both fixed and portable applications. This level of integration benefits the customer by reducing design cost and footprint and communication with the device is accomplished via the industry-wide I?C interface standard.

"The ISL12024/25 feature an I?C communication link, which provides a reliable communication channel for the unique ID," said Rouben Gharagozian, marketing director for Intersil's timing products group. "The I?C communication interface is universal and communicates with all devices on the board, saving design time and simplifying the entire system."

Accurate time keeping
With on-chip timing and crystal compensation, these devices allow tuning of the crystal frequency through the MCU 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 64bit 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.

Polled alarm
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.

The ISL12024 is available today in 8-lead SOIC and TSSOP packages, with prices starting at $1.80 each. The ISL12025 is available today in 8-lead SOIC and TSSOP packages, with prices starting at $1.97 each. All pricing is in 1,000-unit quantities.




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