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