Intersil’s Real-Time Clocks Compensate for Drift Over Time and Temperature

Intersil’s ISL1218/20 Feature Timing and Crystal Compensation, I2C Interface, Power Fail Indicator, Intelligent Battery Backup Switching, Periodic or Polled Alarm and 8 Bytes of Battery-Backed User SRAM

Intersil Corporation (NASDAQ: ISIL), a world leader in the design and manufacture of high-performance analog semiconductors, today introduced two new micropower real-time clock/calendar devices. The ISL1218 and ISL1220 with on-chip timing and crystal compensation deliver accurate timekeeping with very low power dissipation.

The accuracy of an RTC typically depends on the frequency of the external crystal that is used as the time basis. However, the ISL1218/20 allow designers to adjust integrated analog and digital timing registers to trim the internal oscillator for initial accuracy.

“The designer can adjust the on-chip oscillator through I2C digital interface,” said Rouben Gharagozian, marketing director for Intersil’s Timing products group. “The analog trimming register calibrates on-chip digital capacitors and the digital timing register adjusts the timing counter. This finally makes using a lower-cost, 32.768kHz quartz crystal a practical and accurate option.”

Cost and Space Savings
The ISL1218/20 also feature power failure detection, periodic or polled alarm, intelligent battery backup switching, 8 bytes of battery backed SRAM (static random access memory) and Intersil’s battery-saving InterSeal™ technology to prevent initial battery drain prior to first use. The ISL1220 has a separate FOUT pin to allow clocking of the micro through RTC while having a separate alarm pin. The ISL1218 is housed in an 8-lead SOIC or MSOP package, and the ISL1220 is housed in a 10-lead MSOP package. Small packaging and integrated functionality combine to save designers cost and board space.

Intersil’s Trademarked InterSeal™ Battery-Saving Feature
Intersil’s InterSeal™ Battery Saver prevents initial battery current drain before the devices are first used. For example, battery-backed RTCs are commonly packaged on a board with a battery connected. In order to preserve battery life, these devices will not draw any power from the battery source until after the device is first powered up from the VDD source.

Periodic or 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 device can be configured to provide a hardware interrupt via the IRQ pin. There is a repeat mode for the alarm allowing a periodic interrupt every minute, every hour, every day, etc.

Key Features
•Real-time clock/calendar
oTracks time in hours, minutes, and seconds
oDay of the week, day, month, and year
•15 selectable frequency outputs
•Single alarm
oProgrammable to the second, minute, hour, day of the week, day or month
oSingle event or pulse interrupt mode
•Automatic backup to battery or super cap
•Power failure detection
•On-chip oscillator compensation
•8 bytes battery-backed user SRAM
•I2C interface
o400kHz data transfer rate
•400nA battery supply current
•Same pin out as ST M41Txx and Maxim DS13xx devices
•Small package options
o8- and 10-lead MSOP and SOIC packages
•Pb-free plus anneal available (RoHS compliant)
Target Applications

•Industrial, including power meters, control units, security systems, ATMs, cameras, vending machines and electronic door openers
•Medical, including portable medical instruments, defibrillators and glucose meters
•Handheld units, such as point-of-sale terminals and scanners