DS1685-3+ Real Time Clock IC: Equivalent & Substitute Parts

Part Overview

The DS1685-3+ is a Real Time Clock (RTC) IC with integrated Clock/Calendar functionality, manufactured by Analog Devices Inc./Maxim Integrated. This 24-DIP through-hole component provides 242 bytes of NVSRAM, alarm capability, square wave output, and Y2K compliance. The device operates with a supply voltage range of 2.7V to 3.7V and maintains timekeeping at a maximum current of 2mA at 3V. Currently classified as obsolete, the DS1685-3+ remains available in inventory (2059 pcs new original stock). Due to its obsolete status and limited future availability, identifying functionally equivalent alternatives is necessary for design continuity and long-term component sourcing.

Substiute Parts

DS1685-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 2151DS1685-3+ Datasheet

Current PartRFQ

DS1685-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 2151DS1685-3+ Datasheet

DirectRFQ

DP8573AVX/NOPB

National SemiconductorIn Stock: 1484DP8573AVX/NOPB Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the DS1685-3+ is constrained by several critical parameters that define functional equivalence:

Primary Substitution Criteria:

• Clock/Calendar functionality with parallel interface
• Real Time Clock with alarm capability
• NVSRAM or equivalent non-volatile memory
• Time and date format support (HH:MM:SS and YY-MM-DD-dd)
• Through-hole or surface-mount packaging options
• Supply voltage compatibility or acceptable range overlap
• Operating temperature range suitable for the application environment

Substitution Limitations: The DP8573AVX/NOPB, while functionally a Clock/Calendar RTC with parallel interface, operates at a different voltage range (4.5V ~ 5.5V supply) compared to the DS1685-3+ (2.7V ~ 3.7V). This voltage differential represents a significant design constraint. Additionally, the DP8573AVX/NOPB uses 28-LCC surface-mount packaging rather than the 24-DIP through-hole format of the original part. These differences require circuit redesign and board layout modifications.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Same Voltage Domain): The DS1685-3+ remains the primary choice when 2.7V to 3.7V supply voltage is required and through-hole 24-DIP packaging is specified. Current inventory of 2059 pcs new original stock supports near-term production requirements. The part maintains ROHS3 compliance and MSL-1 rating.

For Alternative Selection (Design Modification Required): The DP8573AVX/NOPB is suitable only when circuit redesign accommodates 4.5V to 5.5V supply voltage operation and surface-mount 28-LCC packaging is acceptable. This substitute is currently in active production status (1453 pcs inventory), providing superior long-term availability compared to the obsolete DS1685-3+. The DP8573AVX/NOPB offers extended operating temperature range (-40°C to 85°C) and lower timekeeping current consumption (1µA @ 5V). However, RoHS compliance status for the DP8573AVX/NOPB is not specified in available documentation and must be verified independently.

Voltage Incompatibility Consideration: Direct pin-for-pin substitution is not feasible due to non-overlapping primary supply voltage ranges. Any transition to DP8573AVX/NOPB requires full circuit redesign, including voltage regulation modifications and board layout changes.

Frequently Asked Questions (FAQ)

Q: Can the DP8573AVX/NOPB replace the DS1685-3+ without circuit modifications?

A: No. The DP8573AVX/NOPB operates at 4.5V to 5.5V supply voltage, while the DS1685-3+ requires 2.7V to 3.7V. Additionally, the DP8573AVX/NOPB uses 28-LCC surface-mount packaging versus the 24-DIP through-hole format of the DS1685-3+. Both voltage regulation and board layout redesign are necessary.

Q: What are the key functional differences between these parts?

A: Both devices provide Clock/Calendar functionality with parallel interface, alarm capability, and date/time format support. The DS1685-3+ includes square wave output and NVSRAM; the DP8573AVX/NOPB specifies leap year support. The DP8573AVX/NOPB operates at higher supply voltage and lower timekeeping current, with extended temperature range.

Q: Is the DS1685-3+ still available for new designs?

A: The DS1685-3+ is classified as obsolete. While 2059 pcs remain in current inventory, this represents finite stock. New designs should evaluate active alternatives such as the DP8573AVX/NOPB if long-term component availability is a requirement.

Q: What packaging considerations apply to substitution?

A: The DS1685-3+ uses through-hole 24-DIP (0.600", 15.24mm) mounting. The DP8573AVX/NOPB uses surface-mount 28-LCC (J-Lead) packaging. Through-hole and surface-mount technologies require different PCB design, assembly processes, and manufacturing capabilities.

Q: Are both parts RoHS compliant?

A: The DS1685-3+ is ROHS3 compliant. RoHS compliance status for the DP8573AVX/NOPB is not specified in the provided technical data and must be verified with the manufacturer or authorized distributor.

Q: What is the battery backup voltage range for each part?

A: DS1685-3+ battery supply: 2.5V to 3.7V. DP8573AVX/NOPB battery supply: 2.2V to 5.1V. The DP8573AVX/NOPB supports a wider battery voltage range, including compatibility with lower-voltage backup sources.