DS1688S+ Equivalent & Substitute Parts

Part Overview

The DS1688S+ is a Real Time Clock (RTC) IC with Clock/Calendar functionality manufactured by Analog Devices Inc./Maxim Integrated. This device provides parallel interface timekeeping with alarm, leap year, square wave output, and unique ID features in a 28-SOIC surface mount package. The DS1688S+ is classified as obsolete, making equivalent and substitute parts necessary for ongoing system support and new design implementations. Substitute parts must maintain functional compatibility across clock/calendar operations, parallel interface architecture, and operating temperature ranges while accommodating different packaging and supply voltage specifications.

Substiute Parts

DS1688S+

Analog Devices Inc./Maxim IntegratedIn Stock: 1072DS1688S+ Datasheet

Current PartRFQ

BQ4802LYPWR

Texas InstrumentsIn Stock: 28912BQ4802LYPWR Datasheet

MFR RecommendedRFQ

M48T08-100PC1

STMicroelectronicsIn Stock: 1683M48T08-100PC1 Datasheet

MFR RecommendedRFQ

M48T18-100PC1

STMicroelectronicsIn Stock: 1462M48T18-100PC1 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution logic for the DS1688S+ is based on the following critical parameters that determine functional compatibility:

Primary Compatibility Criteria:

• Parallel interface architecture (required for direct pin-level compatibility)
• Clock/Calendar functionality with HH:MM:SS time format and YY-MM-DD date format
• Operating temperature range of 0°C ~ 70°C
• RoHS3 compliance and EAR99 export classification
• 28-pin package configuration

Secondary Compatibility Considerations:

• Supply voltage ranges (dual voltage support preferred but single range acceptable with design modification)
• Leap year and alarm features (core RTC functionality)
• Mounting type (surface mount or through-hole depending on PCB design)
• Current consumption specifications for power budget analysis

The substitute parts listed below maintain these core parameters while accommodating variations in packaging format, supply voltage specifications, and additional supervisory features.

Parameter Comparison

Engineering Selection Recommendations

BQ4802LYPWR (Texas Instruments)

The BQ4802LYPWR is an active product offering the closest functional alignment to the DS1688S+ for surface mount applications. This device maintains parallel interface architecture, dual time format support (12/24 hour), and identical operating temperature range. The 28-TSSOP package provides a smaller footprint than the original 28-SOIC while maintaining 28-pin configuration. Supply voltage specification of 2.7V ~ 3.6V covers the lower voltage range of the DS1688S+ but does not extend to 5.5V operation. Additional features include daylight savings time, supervisor, and watchdog timer functionality. This part is recommended for new designs requiring surface mount packaging and lower voltage operation.

M48T08-100PC1 (STMicroelectronics)

The M48T08-100PC1 is an active product from the Timekeeper® series suitable for through-hole applications. This device maintains parallel interface architecture and clock/calendar functionality with 24-hour time format and YY-MM-DD-dd date format. The 28-DIP Module package accommodates through-hole mounting on legacy PCB designs. Supply voltage specification of 4.75V ~ 5.5V restricts operation to the upper voltage range of the DS1688S+. Current consumption of 3mA at 4.7V ~ 5.5V provides power budget reference for system design. This part is recommended for legacy system support and through-hole PCB implementations.

M48T18-100PC1 (STMicroelectronics)

The M48T18-100PC1 is an active product from the Timekeeper® series offering through-hole mounting compatibility. This device maintains parallel interface architecture and clock/calendar functionality with 24-hour time format and YY-MM-DD-dd date format. The 28-DIP Module package accommodates through-hole mounting on legacy PCB designs. Supply voltage specification of 4.5V ~ 5.5V provides broader coverage of the upper voltage range compared to M48T08-100PC1. Current consumption of 3mA at 4.5V ~ 5.5V provides power budget reference for system design. This part is recommended for legacy system support and through-hole PCB implementations requiring extended lower voltage operation within the 5V range.

All substitute parts maintain ROHS3 compliance and EAR99 export classification consistent with the original DS1688S+ device.

Frequently Asked Questions (FAQ)

Q: Can the BQ4802LYPWR directly replace the DS1688S+ in existing designs?

A: The BQ4802LYPWR maintains parallel interface architecture, clock/calendar functionality, and identical operating temperature range. However, the supply voltage specification differs: BQ4802LYPWR operates at 2.7V ~ 3.6V while DS1688S+ supports 2.7V ~ 3.3V and 4.5V ~ 5.5V. Direct replacement is feasible for designs operating within the 2.7V ~ 3.3V range. Designs requiring 5V operation require alternative substitutes. Package change from 28-SOIC to 28-TSSOP requires PCB layout modification.

Q: What are the key differences between the M48T08-100PC1 and M48T18-100PC1?

A: Both devices are STMicroelectronics Timekeeper® series parts with identical 28-DIP Module through-hole packaging and parallel interface architecture. The primary difference is supply voltage specification: M48T08-100PC1 operates at 4.75V ~ 5.5V while M48T18-100PC1 operates at 4.5V ~ 5.5V. The M48T18-100PC1 provides extended lower voltage operation within the 5V range. Both devices support 24-hour time format and include leap year and watchdog timer features.

Q: Are the STMicroelectronics parts suitable for new surface mount designs?

A: No. The M48T08-100PC1 and M48T18-100PC1 are through-hole 28-DIP Module packages designed for legacy PCB implementations. For new surface mount designs, the BQ4802LYPWR in 28-TSSOP package is the appropriate choice among the listed substitutes.

Q: What is the impact of time format differences between 12/24 hour and 24-hour only operation?

A: The DS1688S+ supports both 12-hour and 24-hour time formats. The BQ4802LYPWR also supports both formats. The M48T08-100PC1 and M48T18-100PC1 support 24-hour format only. Designs requiring 12-hour time format operation must use either the DS1688S+ or BQ4802LYPWR.

Q: How do the additional features in BQ4802LYPWR affect substitution compatibility?

A: The BQ4802LYPWR includes daylight savings time, supervisor, and watchdog timer features not present in the DS1688S+. These additional features do not prevent substitution; they represent functional enhancements. Existing firmware and hardware designs do not require modification to accommodate these features. The core clock/calendar and parallel interface functionality remain compatible.

Q: What packaging considerations apply when substituting the DS1688S+?

A: The DS1688S+ uses 28-SOIC surface mount packaging. The BQ4802LYPWR uses 28-TSSOP surface mount packaging with different pin pitch and footprint, requiring PCB layout modification. The M48T08-100PC1 and M48T18-100PC1 use 28-DIP Module through-hole packaging, requiring complete PCB redesign for mounting. Package selection depends on existing PCB design constraints and manufacturing capabilities.