DS1691

Real Time Clock Overview

The DS1691 is a serialized real-time clock (RTC) module designed as a successor to the industry-standard DS1285 PC RTC. It integrates the DS1688 IC, a 32.768kHz crystal, and a lithium battery into a single self-contained unit housed in a 28-pin EDIP package. The device supports +3V or +5V operation with automatic backup and write protection for external SRAM via VCCO and CEO pins. Key features include a unique 64-bit silicon serial number, power-on elapsed timer, power-cycle counter, and a 32-bit VBAT-powered continuous counter. Timekeeping includes leap year compensation valid up to the year 2100.

Real Time Clock Feature Summary

• Integrated Module: Combines DS1688 RTC, 32.768kHz crystal, and lithium battery in a 28-pin EDIP package.
• Serialized Identity: Includes a unique 64-bit silicon serial number and optional 64-bit customer-specific ROM.
• Power Management: Features power-on interrupt output (PWR), 32kHz square-wave output, and auxiliary battery input.
• External Memory Control: Provides automatic battery backup and write protection for external SRAM through VCCO and CEO pins.

Real Time Clock Applications

• PC Real-Time Clocks
• System Power-On Triggering via Date/Time Alarm
• Maintenance Tracking and Warranty Requirements

Real Time Clock Procurement Notes

Verify that the specific order corresponds to the standalone DS1691 module rather than the discrete DS1688 IC. Confirm the package type is 28 EDIP. Ensure the application design accounts for the integrated lithium battery lifespan and the requirement for an external SRAM if NV RAM control is utilized.

Real Time Clock Selection Notes

Select the DS1691 when a pre-assembled RTC solution with an embedded battery and crystal is required. This component is suitable for designs needing system wake-up capabilities triggered by time alarms or key closures. Verify compatibility with existing BIOS standards intended for original DS1287 functions.

Real Time Clock Part Context

The DS1691 serves as the module version of the DS1688 serialized RTC. While the DS1688 is a standalone IC requiring external components, the DS1691 provides a complete timekeeping solution with guaranteed minimum 10 years of data retention in the absence of VCC. It is part of the Maxim/Dallas Semiconductor line of serialized clocks.

Real Time Clock Replacement Considerations

The DS1688S is the equivalent discrete IC component. For direct replacement, verify that the host board can accommodate the separate crystal and battery assembly required by the DS1688S, as the DS1691 is a self-contained module.

Real Time Clock FAQ

What is the difference between the DS1688 and DS1691?

The DS1688 is a standalone IC, whereas the DS1691 is a complete module that incorporates the DS1688 IC, a 32.768kHz crystal, and a lithium battery in a single 28-pin EDIP package.

How does the DS1691 handle external memory?

It provides automatic backup and write protection for external SRAM using the VCCO pin for power and the CEO pin for chip enable control during power transients.

Can the DS1691 trigger system power-on?

Yes, the PWR output pin can be triggered by a date/time alarm or a key closure to turn on an external power supply.