Features: *Integrated NV SRAM, Real-Time Clock, Crystal, Power-Fail Control Circuit and Lithium Energy Source
*Clock Registers are Accessed Identically to the Static RAM. These Registers are Resident in the Eight Top RAM Locations.
*Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power
*BCD-Coded Year, Month, Date, Day, Hours,Minutes, and Seconds with Leap Year Compensation Valid Up to 2100
*Power-Fail Write Protection Allows for ±10% VCC Power Supply Tolerance
*DS1644 Only (DIP Module) Upward Compatible with the DS1643 Timekeeping RAM to Achieve Higher RAM Density Standard JEDEC Bytewide 32k x 8 Static RAM Pinout
*DS1644P Only (PowerCap(R) Module Board) Surface Mountable Package for Direct Connection to PowerCap Containing Battery and crystal Replaceable Battery (PowerCap) Power-Fail Output Pin-for-Pin Compatible with Other Densities of DS164XP Timekeeping RAM
nderwriters Laboratory (UL) Recognized
Pinout
SpecificationsVoltage Range on Any Pin Relative to Ground........ ..-0.3V to +7.0V
Storage Temperature...............-40 to +85, Noncondensing
Soldering Temperature..+260 for 10 seconds (DIP Package) (See Note 7)
See IPC/JEDEC Standard J-STD-020A for Surface-Mount Devices Description The DS1644 is a 32k x 8 nonvolatile static RAM with a full function real time clock, which are both accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any JEDEC standard 32k x 8 SRAM. The device DS1644 can also be easily substituted for ROM, EPROM and EEPROM, providing read/write nonvolatility and the addition of the real time clock function. The real ime clock nformation 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 DS1644 are double-buffered to avoid access of incorrect data that can occur during clock update cycles. The double-buffered system also prevents ime loss as the timekeeping countdown continues unabated by access to time register data. The DS1644 also contains its own power-fail circuitry, which deselects the device DS1644 when the VCC supply is in an out-of-olerance condition. This feature prevents loss of data from unpredictable system operation brought on by ow VCC as errant access and update cycles are avoided.
DS1644 Data Sheet
