GENERAL DESCRIPTION
The DS1688/DS1691 are real-time clocks (RTCs) designed as successors to the industry standard DS1285, DS1385, DS1485, and DS1585 PC real-time clocks. These devices provide the industry standard DS1285 clock function with the new feature of either +3.0V or +5.0V operation and automatic backup and write protection to an external SRAM.

FEATURES
Incorporates Industry Standard DS1287 PC Clock Plus Enhanced Features:
■ +3V or +5V Operation
■ 64-Bit Silicon Serial Number
■ 64-Bit Customer Specific ROM or Additional Serial Number Available
■ Power Control Circuitry Supports System Power-On from Date/Time Alarm or Key Closure
■ Automatic Battery Backup and Write Protection to External SRAM
■ Crystal Select Bit Allows RTC to Operate with 6Pf or 12.5Pf Crystal
■ 114 Bytes User NV RAM
■ Auxiliary Battery Input
■ RAM Clear Input
■ Century Register
■ 32kHz Output for Power Management
■ 32-Bit VCC Powered Elapsed Time Counter
■ 32-Bit VBAT Powered Elapsed Time Counter
■ 16-Bit Power-Cycle Counter
■ Compatible with Existing BIOS for Original DS1287 Functions
■ Available as IC (DS1688) or Stand-Alone Module with Embedded Battery and Crystal (DS1691)
■ Timekeeping Algorithm Includes Leap Year Compensation Valid Up to 2100