BQ3285LDSSTR Equivalent & Substitute Parts

Part Overview

The BQ3285LDSSTR is a Real Time Clock (RTC) IC with integrated Clock/Calendar functionality, 242B of parallel memory, and alarm capabilities. Manufactured by Texas Instruments in a 24-SSOP surface mount package, this component is classified as obsolete. Due to its discontinued status, equivalent substitute parts from active product lines are necessary for new designs and ongoing system support.

Key Parameters

Parameter	BQ3285LDSSTR
Manufacturer	Texas Instruments
Product Status	Obsolete
Type	Clock/Calendar
Memory Size	242B
Interface	Parallel
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Voltage - Supply	2.7V ~ 5.5V
Voltage - Supply, Battery	2.4V ~ 4V
Current - Timekeeping (Max)	100µA @ 3V
Operating Temperature	0°C ~ 70°C
Mounting Type	Surface Mount
Package / Case	24-SSOP (0.154", 3.90mm Width)
Features	Alarm, Daylight Savings, NVSRAM
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the BQ3285LDSSTR is determined by the following critical parameters:

Primary Compatibility Criteria:

Parallel interface (required for pin-level compatibility)
Memory size of 242B (functional equivalence for data storage)
Time format support for 12/24 hour operation
Date format support for YY-MM-DD-dd
Supply voltage overlap within 2.7V ~ 5.5V range
Operating temperature range minimum of 0°C
Surface mount or through-hole mounting (package-dependent substitution)
NVSRAM feature (non-volatile static RAM for data retention)

Substitute parts are grouped into two categories based on package type:

Surface Mount Substitutes (Direct Package Compatibility): DS1685S-3+T&R matches the 24-SOIC surface mount form factor with identical memory capacity and feature set.

Through-Hole and Module Substitutes (Functional Equivalence): DS1687-3+ provides 24-DIP module packaging with equivalent memory and features for through-hole applications. DS1744 series parts (DS1744W-120+, DS1744P-70+, DS1744WP-120IND+) and DS1746WP-120+ offer higher memory capacity (32KB or 128KB) in module packages for applications requiring expanded storage.

Extended Feature Substitutes: DS12885QN+T&R, DS1554WP-120IND+, DS1556-70+, and DS1747-70IND+ provide additional features such as watchdog timers, leap year support, and Y2K compliance with varying memory configurations and package options.

Parameter Comparison

Parameter	BQ3285LDSSTR	DS1685S-3+T&R	DS1687-3+	DS1744W-120+	DS1744P-70+	DS1744WP-120IND+	DS1746WP-120+	DS1554WP-120IND+	DS1556-70+	DS1747-70IND+	DS12885QN+T&R
Manufacturer	Texas Instruments	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated	Analog Devices Inc./Maxim Integrated
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active	Active	Active
Type	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar
Memory Size	242B	242B	242B	32KB	32KB	32KB	128KB	32KB	128KB	512KB	114B
Interface	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd
Voltage - Supply	2.7V ~ 5.5V	2.7V ~ 3.7V	2.7V ~ 3.7V	2.97V ~ 3.63V	4.5V ~ 5.5V	2.97V ~ 3.63V	2.97V ~ 3.63V	2.97V ~ 3.63V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V
Voltage - Supply, Battery	2.4V ~ 4V	2.5V ~ 3.7V	2.5V ~ 3.7V	—	3V	3V	3V	3V	—	—	2.5V ~ 4V
Current - Timekeeping (Max)	100µA @ 3V	2mA @ 3V	2mA @ 3V	2mA @ 3.3V	4mA @ 5V	2mA @ 3.3V	2mA @ 3.3V	4mA @ 3.3V	6mA @ 5V	4mA @ 5V	15mA @ 4.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	-40°C ~ 85°C	0°C ~ 70°C	-40°C ~ 85°C	0°C ~ 70°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Through Hole	Through Hole	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Through Hole	Through Hole	Surface Mount
Package / Case	24-SSOP (0.154", 3.90mm Width)	24-SOIC (0.295", 7.50mm Width)	24-DIP Module (0.600", 15.24mm)	28-DIP Module (0.600", 15.24mm)	34-PowerCap™ Module	34-PowerCap™ Module	34-PowerCap™ Module	34-PowerCap™ Module	32-DIP Module (0.600", 15.24mm)	32-DIP Module (0.600", 15.24mm)	28-LCC (J-Lead)
Features	Alarm, Daylight Savings, NVSRAM	Alarm, NVSRAM, Square Wave Output, Y2K	Alarm, NVSRAM, Square Wave Output, Y2K	Leap Year, NVSRAM, Y2K	Leap Year, NVSRAM, Y2K	Leap Year, NVSRAM, Y2K	Leap Year, NVSRAM, Y2K	Alarm, Leap Year, NVSRAM, Watchdog Timer, Y2K	Alarm, Leap Year, NVSRAM, Watchdog Timer, Y2K	Leap Year, NVSRAM, Y2K	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Surface Mount Replacement (Identical Package Form Factor): DS1685S-3+T&R is the primary equivalent for the BQ3285LDSSTR. Both components feature 242B memory capacity, parallel interface, and 12/24 hour time format support. DS1685S-3+T&R operates at 2.7V ~ 3.7V supply voltage, which overlaps with the lower range of the original part. This part is active and ROHS3 compliant, ensuring long-term availability and regulatory compliance.

For Through-Hole Applications: DS1687-3+ provides equivalent functionality in a 24-DIP module package. It maintains 242B memory, parallel interface, and identical operating temperature range (0°C ~ 70°C). This part is active and suitable for legacy board designs requiring through-hole components.

For Extended Memory Requirements: DS1744 series parts (DS1744W-120+, DS1744P-70+, DS1744WP-120IND+) and DS1746WP-120+ offer 32KB or 128KB memory in PowerCap™ module packages. These are active products with ROHS3 compliance. DS1744WP-120IND+ extends the operating temperature range to -40°C ~ 85°C, suitable for industrial applications.

For Maximum Memory and Extended Temperature Range: DS1747-70IND+ provides 512KB memory in a 32-DIP module package with -40°C ~ 85°C operating temperature. This part is active and ROHS3 compliant for demanding applications.

For 28-Pin PLCC Package: DS12885QN+T&R offers 114B memory with extended operating temperature (-40°C ~ 85°C) and is active with ROHS3 compliance. This part includes daylight savings and leap year support.

All substitute parts are manufactured by Analog Devices Inc./Maxim Integrated, an active supplier with established distribution channels. All listed substitutes maintain ROHS3 compliance and REACH unaffected status, matching the regulatory profile of the original BQ3285LDSSTR.

Frequently Asked Questions (FAQ)

Q: Can DS1685S-3+T&R directly replace BQ3285LDSSTR on existing PCBs? A: DS1685S-3+T&R uses a 24-SOIC package while BQ3285LDSSTR uses 24-SSOP. Both are surface mount packages with different pitch and body dimensions. PCB layout modification is required. Pin-level compatibility must be verified against the specific application schematic.

Q: What is the key difference between 242B and 32KB memory options? A: BQ3285LDSSTR and DS1685S-3+T&R both provide 242 bytes of memory. DS1744 series parts provide 32KB (32,768 bytes), offering significantly expanded storage for applications requiring larger data buffers. DS1746WP-120+ and DS1747-70IND+ provide 128KB and 512KB respectively.

Q: Are all substitute parts ROHS3 compliant? A: Yes. All listed substitute parts are ROHS3 compliant and REACH unaffected, matching the regulatory status of the original BQ3285LDSSTR.

Q: Which substitute supports the widest operating temperature range? A: DS1744WP-120IND+, DS1554WP-120IND+, DS1747-70IND+, and DS12885QN+T&R all support -40°C ~ 85°C operating temperature, compared to the original part's 0°C ~ 70°C range.

Q: What is the supply voltage compatibility consideration? A: BQ3285LDSSTR operates at 2.7V ~ 5.5V. DS1685S-3+T&R operates at 2.7V ~ 3.7V, requiring verification that system supply voltage does not exceed 3.7V. DS1744P-70+ and DS1556-70+ operate at 4.5V ~ 5.5V, suitable for 5V systems. Verify system voltage requirements before selection.

Q: Do all substitutes support 12/24 hour time format? A: DS1685S-3+T&R and DS12885QN+T&R support 12/24 hour format. DS1744 series, DS1746WP-120+, DS1554WP-120IND+, DS1556-70+, and DS1747-70IND+ support 24-hour format only. Application firmware must accommodate this difference.

Q: What packaging options are available for surface mount applications? A: DS1685S-3+T&R (24-SOIC), DS1744P-70+ (34-PowerCap™ Module), DS1744WP-120IND+ (34-PowerCap™ Module), DS1746WP-120+ (34-PowerCap™ Module), DS1554WP-120IND+ (34-PowerCap™ Module), and DS12885QN+T&R (28-LCC J-Lead) are surface mount options.

Q: Which substitute has the lowest timekeeping current consumption? A: DS1685S-3+T&R, DS1687-3+, DS1744W-120+, and DS1744WP-120IND+ all consume 2mA @ 3V or 3.3V during timekeeping operation, lower than the original part's 100µA @ 3V specification. DS1746WP-120+ also consumes 2mA @ 3.3V.

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