DS1688S+

Real Time Clock Overview

The DS1688S+ is a serialized real-time clock (RTC) IC designed as a successor to the DS1285 standard. It operates on a multiplexed bus interface with a supply voltage range of 3V to 5V and supports an operating temperature from 0°C to +70°C in a 28-pin SO package. The device integrates 114 bytes of user-accessible nonvolatile SRAM controlled via VCCO and CEO pins. Key features include a unique 64-bit silicon serial number, power-on elapsed timer, power-cycle counter, and auxiliary battery input. It provides automatic backup and write protection for external SRAM during power transients.

Real Time Clock Feature Summary

• Incorporates a unique 64-bit silicon serial number and optional 64-bit customer-specific ROM for system identification.
• Provides 114 bytes of user NV SRAM with automatic battery backup and write protection via VCCO/CEO pins.
• Includes power control circuitry allowing system power-on via date/time alarm or key closure through the PWR output pin.
• Features a 32kHz square-wave output for power management and leap year compensation valid up to the year 2100.

Real Time Clock Applications

• PC real-time clock systems requiring industry-standard DS1285 compatibility.
• Systems needing electronic identification via unique serial numbers for network node addressing.
• Applications requiring maintenance tracking using power-on elapsed time and cycle counters.
• Portable or embedded systems utilizing auxiliary battery inputs for extended timekeeping reliability.

Real Time Clock Procurement Notes

Verify the specific ordering suffix against the manufacturer's current documentation to confirm lead-free status and package type. The 'S' designation indicates a 28-pin Small Outline package. Confirm availability status as discontinued products may require alternative sourcing strategies.

Real Time Clock Selection Notes

Select the DS1688S+ when a multiplexed bus interface is required alongside integrated NV RAM control. Ensure the design accommodates the 3V to 5V operating range and utilizes the dedicated VCCO and CEO pins for external SRAM management. Verify crystal selection matches the 6pF or 12.5pF capacitance settings supported by the device.

Real Time Clock Part Context

The DS1688 series serves as an enhanced replacement for legacy DS1285, DS1385, DS1485, and DS1585 RTCs. While the DS1691 variant offers a self-contained module with an embedded battery and crystal, the DS1688S+ is the standalone IC version intended for integration into custom PCB designs requiring external components.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided source material.