DS1685S-3 Real Time Clock IC Equivalent & Substitute Parts

Part Overview

The DS1685S-3 is a Real Time Clock (RTC) IC with integrated Clock/Calendar functionality, manufactured by Analog Devices Inc./Maxim Integrated. This device provides 242 bytes of NVSRAM, parallel interface, and features including alarm capability, square wave output, and Y2K compliance. The DS1685S-3 is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Active alternatives with compatible electrical and mechanical specifications are available from multiple manufacturers.

Substiute Parts

DS1685S-3

Analog Devices Inc./Maxim IntegratedIn Stock: 1399DS1685S-3 Datasheet

Current PartRFQ

DS1685S-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 1114DS1685S-3+ Datasheet

DirectRFQ

BQ4802LYDW

Texas InstrumentsIn Stock: 1993BQ4802LYDW Datasheet

MFR RecommendedRFQ

BQ4802LYPW

Texas InstrumentsIn Stock: 9564BQ4802LYPW Datasheet

MFR RecommendedRFQ

M48T58Y-70MH1F

STMicroelectronicsIn Stock: 2289M48T58Y-70MH1F Datasheet

MFR RecommendedRFQ

M48T58Y-70PC1

STMicroelectronicsIn Stock: 1732M48T58Y-70PC1 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the DS1685S-3 is determined by the following critical parameters:

Primary Compatibility Criteria:

• Parallel interface requirement
• Time format support (12/24 hour)
• Date format support (YY-MM-DD-dd)
• Operating temperature range (0°C ~ 70°C)
• Supply voltage compatibility (2.7V ~ 3.7V nominal range)
• Surface mount packaging

Substitution Categories:

Direct Equivalent (Same Package): DS1685S-3+ maintains identical electrical specifications and 24-SOIC packaging, differing only in product status (Active vs. Obsolete) and RoHS compliance.

Compatible Alternatives (Different Package): BQ4802LYDW, BQ4802LYPW, M48T58Y-70MH1F, and M48T58Y-70PC1 provide equivalent RTC Clock/Calendar functionality with parallel interface and compatible time/date formats. These parts accommodate different packaging requirements (28-SOIC, 28-TSSOP, 28-SOH, 28-DIP) and may have variations in supply voltage ranges, current consumption, and feature sets.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Same Package, Same Electrical Specifications): DS1685S-3+ is the primary choice when package footprint and electrical specifications must remain unchanged. This part maintains 24-SOIC packaging and identical supply voltage range (2.7V ~ 3.7V). The DS1685S-3+ is Active status and ROHS3 compliant, addressing obsolescence and regulatory compliance concerns of the original DS1685S-3.

For Low-Voltage 3.3V Systems (Alternative Packages): BQ4802LYDW and BQ4802LYPW are suitable for designs operating at 2.7V ~ 3.6V supply voltage. Both parts are Active status and ROHS3 compliant. BQ4802LYDW uses 28-SOIC packaging (0.295", 7.50mm Width), while BQ4802LYPW uses 28-TSSOP packaging (0.173", 4.40mm Width). These parts include additional features (Daylight Savings, Supervisor, Watchdog Timer) and lower typical timekeeping current (1.5mA vs. 2mA).

For 5V Systems (Alternative Packages): M48T58Y-70MH1F and M48T58Y-70PC1 operate at 4.5V ~ 5.5V supply voltage and are suitable for legacy 5V designs. M48T58Y-70MH1F uses 28-SOIC packaging with SNAPHAT Sockets (0.337", 8.56mm Width) for surface mount applications. M48T58Y-70PC1 uses 28-DIP Module packaging (0.600", 15.24mm) for through-hole applications. Both are Active status and ROHS3 compliant.

Compliance Considerations: All substitute parts listed are ROHS3 compliant and REACH unaffected, addressing regulatory requirements not met by the obsolete DS1685S-3 (RoHS non-compliant).

Frequently Asked Questions (FAQ)

Q: Can DS1685S-3+ be used as a direct replacement for DS1685S-3? A: Yes. DS1685S-3+ maintains identical electrical specifications, 24-SOIC packaging, and pinout. The primary differences are product status (Active vs. Obsolete) and RoHS compliance (ROHS3 vs. non-compliant). No circuit modifications are required.

Q: What are the key differences between the DS1685S-3 and BQ4802 series? A: Both provide parallel RTC Clock/Calendar functionality with compatible time/date formats and operating temperature ranges. Key differences include package size (24-SOIC vs. 28-SOIC/28-TSSOP), supply voltage range (2.7V~3.7V vs. 2.7V~3.6V), and feature set (BQ4802 includes Daylight Savings, Supervisor, and Watchdog Timer). BQ4802 parts have lower typical timekeeping current consumption.

Q: Can M48T58Y series parts replace DS1685S-3 in 3.3V designs? A: No. M48T58Y series parts require 4.5V ~ 5.5V supply voltage and are not compatible with 3.3V systems. These parts are suitable only for legacy 5V designs.

Q: What packaging options are available for low-voltage RTC substitutes? A: For 2.7V ~ 3.6V systems, BQ4802LYDW provides 28-SOIC (0.295", 7.50mm Width) surface mount packaging, and BQ4802LYPW provides 28-TSSOP (0.173", 4.40mm Width) surface mount packaging. Both are Active status and ROHS3 compliant.

Q: Are all substitute parts ROHS3 compliant? A: Yes. All substitute parts listed (DS1685S-3+, BQ4802LYDW, BQ4802LYPW, M48T58Y-70MH1F, M48T58Y-70PC1) are ROHS3 compliant. The original DS1685S-3 is RoHS non-compliant.

Q: What is the difference between 24-SOIC and 28-SOIC packaging? A: 24-SOIC contains 24 pins in a 0.295" (7.50mm) width package. 28-SOIC contains 28 pins in a 0.295" (7.50mm) width package. These are not pin-compatible and require different PCB layouts and sockets.

Q: Can BQ4802LYPW be used in place of BQ4802LYDW? A: Both parts provide identical electrical specifications and are functionally equivalent. The difference is packaging: BQ4802LYDW uses 28-SOIC (0.295", 7.50mm Width), while BQ4802LYPW uses 28-TSSOP (0.173", 4.40mm Width). Selection depends on PCB layout requirements and available board space.