DS1685QN-3+ Real Time Clock IC: Equivalent & Substitute Parts

Part Overview

The DS1685QN-3+ is an Active status Real Time Clock (RTC) IC manufactured by Analog Devices Inc./Maxim Integrated. This Clock/Calendar device integrates 242 bytes of NVSRAM with parallel interface capability, designed for applications requiring accurate timekeeping with alarm functionality and Y2K compliance. The device operates across a 2.7V to 3.7V supply range with battery backup support (2.5V to 3.7V), making it suitable for embedded systems and industrial applications requiring reliable time management. Substitute parts are identified based on matching functional categories, interface types, memory architecture, and operating parameter ranges that permit direct functional replacement in target applications.

Key Parameters

Parameter	DS1685QN-3+ Specification
Manufacturer	Analog Devices Inc./Maxim Integrated
Product Type	Real Time Clock (RTC) IC Clock/Calendar
Interface	Parallel
Memory Size	242 Bytes
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Supply Voltage	2.7V ~ 3.7V
Battery Voltage	2.5V ~ 3.7V
Current - Timekeeping (Max)	2mA @ 3V
Operating Temperature	-40°C ~ 85°C
Package / Case	28-LCC (J-Lead)
Mounting Type	Surface Mount
Features	Alarm, NVSRAM, Square Wave Output, Y2K
Product Status	Active
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the DS1685QN-3+ are identified based on the following critical parameters that determine functional compatibility:

Primary Substitution Criteria:

Product Type: Real Time Clock (RTC) IC Clock/Calendar
Interface: Parallel
Time Format: HH:MM:SS with 12/24 hour capability
Date Format: YY-MM-DD-dd
Mounting Type: Surface Mount
Product Status: Active

Secondary Compatibility Factors:

Supply voltage overlap within operating ranges
Battery backup voltage support
Package form factor (28-pin configurations preferred for direct replacement)
RoHS3 compliance and regulatory alignment
Timekeeping current consumption within acceptable ranges

The three substitute parts identified (BQ4802LYDW, DP8573AVX/NOPB, M48T201V-85MH1F) meet the core functional requirements of parallel-interface RTC Clock/Calendar operation with time and date tracking capabilities. Variations in package type, operating temperature ranges, and specific feature sets are noted in the parameter comparison table below.

Parameter Comparison

Parameter	DS1685QN-3+	BQ4802LYDW	DP8573AVX/NOPB	M48T201V-85MH1F
Manufacturer	Analog Devices Inc./Maxim Integrated	Texas Instruments	National Semiconductor	STMicroelectronics
Product Type	RTC Clock/Calendar	RTC Clock/Calendar	RTC Clock/Calendar	RTC Clock/Calendar
Interface	Parallel	Parallel	Parallel	Parallel
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS:hh (12/24 hr)	HH:MM:SS (24 hr)
Date Format	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd
Supply Voltage	2.7V ~ 3.7V	2.7V ~ 3.6V	4.5V ~ 5.5V	3V ~ 3.6V
Battery Voltage	2.5V ~ 3.7V	2.4V ~ 4V	2.2V ~ 5.1V	3V
Current - Timekeeping (Max)	2mA @ 3V	1.5mA (Typ) @ 2.7V ~ 3.6V	1µA @ 5V	2mA @ 3V ~ 3.6V
Operating Temperature	-40°C ~ 85°C	0°C ~ 70°C	-40°C ~ 85°C	0°C ~ 70°C
Package / Case	28-LCC (J-Lead)	28-SOIC (0.295", 7.50mm Width)	28-LCC (J-Lead)	44-BSOP (0.337", 8.56mm Width)
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Features	Alarm, NVSRAM, Square Wave Output, Y2K	Alarm, Daylight Savings, Leap Year, Supervisor, Watchdog Timer	Alarm, Leap Year	Alarm, Leap Year, Square Wave Output, Supervisor, Watchdog Timer, Y2K
Product Status	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified	ROHS3 Compliant

Engineering Selection Recommendations

DS1685QN-3+ Direct Equivalent: The DS1685QN-3+ itself remains the primary specification part with Active product status and full ROHS3 compliance. Current inventory of 1097 pieces supports immediate procurement.

BQ4802LYDW (Texas Instruments): This substitute operates within a narrower supply voltage range (2.7V ~ 3.6V) compared to the main part (2.7V ~ 3.7V). The 28-SOIC package differs from the 28-LCC form factor, requiring PCB layout modification. Operating temperature range is restricted to 0°C ~ 70°C versus the main part's -40°C ~ 85°C. Timekeeping current is lower at 1.5mA typical. Active product status and ROHS3 compliance are confirmed. Suitable for applications within the 0°C ~ 70°C temperature window with 28-SOIC package compatibility.

DP8573AVX/NOPB (National Semiconductor): This part operates at a significantly higher supply voltage range (4.5V ~ 5.5V), incompatible with the 2.7V ~ 3.7V specification of the main part. The 28-LCC package matches the original form factor. Operating temperature range matches the main part (-40°C ~ 85°C). Timekeeping current is exceptionally low at 1µA @ 5V. This substitute is not recommended for direct replacement in 3.3V systems due to voltage incompatibility.

M48T201V-85MH1F (STMicroelectronics): This substitute operates within a compatible supply voltage range (3V ~ 3.6V) with fixed 3V battery voltage. The 44-BSOP package represents a significant form factor change from the 28-LCC original, requiring substantial PCB redesign. Operating temperature range is restricted to 0°C ~ 70°C. Timekeeping current matches the main part at 2mA. Active product status and ROHS3 compliance are confirmed. Suitable only for applications permitting 44-pin package integration and 0°C ~ 70°C operation.

Frequently Asked Questions (FAQ)

Q: Can BQ4802LYDW replace DS1685QN-3+ in all applications? A: BQ4802LYDW is functionally compatible for parallel-interface RTC Clock/Calendar applications within the 0°C ~ 70°C operating temperature range. The 28-SOIC package differs from the original 28-LCC form factor, requiring PCB layout verification. Applications requiring -40°C operation must use the original DS1685QN-3+ or DP8573AVX/NOPB.

Q: Why is DP8573AVX/NOPB listed as a substitute if it requires 4.5V ~ 5.5V supply? A: DP8573AVX/NOPB is included as a substitute for applications where 5V supply voltage is available. It is not suitable for direct replacement in 3.3V systems. Voltage compatibility must be verified before selection.

Q: What are the package compatibility implications of M48T201V-85MH1F? A: M48T201V-85MH1F uses a 44-BSOP package versus the original 28-LCC package. This represents a significant form factor change requiring PCB redesign, footprint modification, and pinout verification. This substitute is suitable only for new designs or applications permitting substantial hardware modification.

Q: Are all substitute parts ROHS3 compliant? A: DS1685QN-3+, BQ4802LYDW, and M48T201V-85MH1F are confirmed ROHS3 compliant. DP8573AVX/NOPB RoHS status is not specified in the provided data.

Q: Which substitute offers the lowest timekeeping current consumption? A: DP8573AVX/NOPB operates at 1µA @ 5V, the lowest among all listed parts. However, this advantage is offset by its incompatible 4.5V ~ 5.5V supply voltage requirement for 3.3V systems.

Q: Can substitutes be used interchangeably in existing designs? A: Package form factor differences (28-SOIC for BQ4802LYDW, 44-BSOP for M48T201V-85MH1F) prevent direct PCB interchangeability. Voltage supply compatibility must be verified. Operating temperature range restrictions must be evaluated against application requirements. Each substitute requires individual compatibility assessment before implementation.

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