DS1642-100

Product Summary

The DS1642-100 is a 2K x 8 nonvolatile static RAM with a full function real time clock which are both accessible in a bytewide format. The nonvolatile time keeping RAM is pin and function equivalent to any JEDEC standard 2K x 8 SRAM. The DS1642-100 can also be easily substituted in ROM, EPROM and EEPROM sockets providing read/write nonvolatility and the addition of the real time clock function. The real time clock information resides in the eight uppermost RAM locations. The RTC registers contain year, month, date, day, hours, minutes, and seconds data in 24 hour BCD format. Corrections for the day of the month and leap year are made automatically. The RTC clock registers are double buffered to avoid access of incorrect data that can occur during clock update cycles. The double buffered system also prevents time loss as the timekeeping countdown continues unabated by access to time register data. The DS1642-100 also contains its own power fail circuitry which deselects the device when the VCC supply is in an out of tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by low VCC as errant access and update cycles are avoided.

Parametrics

DS1642-100 absolute maximum ratings: (1)Voltage on Any Pin Relative to Ground: –0.3V to +7.0V; (2)Operating Temperature: 0℃ to 70℃; (3)Storage Temperature: –20℃ to +70℃; (4)Soldering Temperature: 260℃ for 10 seconds.

Features

DS1642-100 features: (1)Integrated NV SRAM, real time clock, crystal, power fail control circuit and lithium energy source; (2)Standard JEDEC bytewide 2K × 8 static RAM pinout; (3)Clock registers are accessed identically to the static RAM. These registers are resident in the eight top RAM locations; (4)Totally nonvolatile with over 10 years of operation in the absence of power; (5)Access times of 70 ns and 100 ns; (6)Quartz accuracy ±1 minute a month @ 25℃, factory calibrated; (7)BCD coded year, month, date, day, hours, minutes, and seconds with leap year compensation valid up to 2100; (8)Power-fail write protection allows for ±10% VCC power supply tolerance; (9)Lithium energy source is electrically disconnected to retain freshness until power is applied for the first time.

Diagrams