Intersil introduced two micropower real-time clock/calendar devices. The ISL1219/21 are dedicated for time stamping single events such as the moment a warranty is voided by the removal of a cover, or recurring events such as the opening and closing of a security door. These devices can time stamp an event by either issuing an output signal or by stopping the real-time clock (RTC) registers from advancing at the moment the event occurs. The output signal contains the second, minute, hour, date, month and year that the triggering event occurred.
The ISL1219/21 offer two options for switching from normal power to battery backup power. All RTC functions except the I2C bus are operational during battery backup mode unless disabled. The user SRAM (static random access memory) is operational until battery power drops below 1.8V. The ISL1219/21 are available in a 10-lead MSOP package and the integrated crystal compensation enables the use of a less expensive external crystal. The ISL1221 has a separate FOUT than the IRQ/FOUT in the ISL1219. The FOUT is the frequency output that is programmable from 32.768 kHz to 1/32 Hz. It is used for a variety of timing applications including the clocking of the microcontroller in sleep mode, eliminating external crystal and further reducing the BOM. On-chip oscillator compensation provides initial crystal frequency trimming through an I2C interface for timing accuracy, enabling the use of a low-cost crystal. The real-time clock tracks time with separate registers for hours, minutes, and seconds.
The device has calendar registers for date, month, year and day of the week. The calendar is accurate through 2099, with automatic leap year correction. Intersil's InterSeal Battery Saver prevents initial battery current drain before the devices are first used. 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. Target appöications are 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.
Pricing and Availability
The ISL1219 is offered in a 10-lead MSOP and is priced at $1.50. The ISL1221 also includes separate FOUT and shared IRQb/EVDETb in a 10-lead MSOP package and is priced at $1.60. All pricing is in 1,000-unit quantities. Intersil also provides evaluation boards for these devices.
