DS1647

Features:

Integrates 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 DS1647 only (DIP Module)
Standard JEDEC byte-wide 128k x 8 RAM pinout
DS1647P only (PowerCap® 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


Specifications

Voltage on Any Pin Relative to Ground             -0.3V to +7.0V
Storage Temperature                                       -40°C to +85°C
Soldering Temperature                                    260°C for 10 seconds (DIP Package) (See Note 7)
See IPC/JEDEC Standard J-STD-020A for Surface Mount Devices

* This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.


Description

The DS1647 is a 512k 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 512k x 8 SRAM. The device DS1647 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- time clock information resides in the eight uppermost RAM locations. The RTC registers DS1647 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 DS1647 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.