DS1747-70

Product Summary

The DS1747-70 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) and 512k x 8 nonvolatile static RAM. User access to all registers within the DS1747-70 is accomplished with a byte-wide interface as shown in Figure 1. The RTC information and control bits reside in the eight uppermost RAM locations. The DS1747-70 contains century, year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the date of each 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 DS1747-70 also contains its own power-fail circuitry that 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

DS1747-70 absolute maximum ratings: (1)Voltage Range on Any Pin Relative to Ground: -0.3V to +6.0V; (2)Storage Temperature Range: -40°C to +85°C; (3)Active Supply Current Icc: 85 mA; (4)Address Access Time tAA: 70 ns.

Features

DS1747-70 features: (1)Integrated NV SRAM, Real-Time Clock (RTC), Crystal, Power-Fail Control Circuit, and Lithium Energy Source; (2)Clock Registers are Accessed Identically to the Static RAM. These Registers are Resident in the Eight Top RAM Locations.; (3)Century Byte Register (Y2K Compliant); (4)Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power; (5)BCD-Coded Century, Year, Month, Date, Day, Hours, Minutes, and Seconds with Automatic Leap-Year Compensation Valid Up to the Year 2100; (6)Battery Voltage-Level Indicator Flag; (7)Power-Fail Write Protection Allows for ±10% VCC Power-Supply Tolerance; (8)Lithium Energy Source is Electrically Disconnected to Retain Freshness Until Power is Applied for the First Time.

Diagrams