The DS1688/DS1691 is a real-time clock (RTC) designed as a successor to the industry standard DS1285, DS1385, DS1485, and DS1585 PC real time clocks. This device provides the industry standard DS1285 clock function with the new feature of either +3.0 or +5.0V operation and automatic backup and write protection to an external SRAM. The DS1688 also incorporates a number of enhanced features including a silicon serial number, power on/off control circuitry, 114 bytes of user NV SRAM, power on elapsed timer, and power cycle counter.
Key Features
Incorporates industry standard DS1287 PC clock plus enhanced features:
+3 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
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