BQ4285S-SB2TR Real Time Clock (RTC) IC Equivalent & Substitute Parts

Part Overview

The BQ4285S-SB2TR is a Real Time Clock (RTC) IC manufactured by Texas Instruments, designed for clock/calendar applications with parallel interface. This device features alarm functionality, daylight savings support, leap year capability, non-volatile static RAM (NVSRAM), and square wave output in a 24-SOIC surface mount package. The product is currently obsolete, making equivalent and substitute parts necessary for ongoing system support, maintenance, and new design implementations requiring compatible RTC functionality.

Key Parameters

Parameter	Value
Manufacturer Part Number	BQ4285S-SB2TR
Manufacturer	Texas Instruments
Category	Clock/Timing
Type	Clock/Calendar
Package / Case	24-SOIC (0.295", 7.50mm Width)
Memory Size	114B
Interface	Parallel
Voltage - Supply	4.5V ~ 5.5V
Voltage - Supply, Battery	2.5V ~ 4V
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Operating Temperature	0°C ~ 70°C
Mounting Type	Surface Mount
Features	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output
Product Status	Obsolete
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the BQ4285S-SB2TR is determined by the following critical parameters:

Primary Substitution Criteria:

Interface type (Parallel)
Package compatibility (24-SOIC surface mount preferred for direct replacement)
Voltage supply range (4.5V ~ 5.5V primary supply)
Time and date format support (HH:MM:SS 12/24 hr, YY-MM-DD-dd)
Feature set (Alarm, Leap Year, NVSRAM, Square Wave Output)
RoHS compliance status

Substitute Categories:

Category 1: Direct Package Replacement (24-SOIC) DS1685E-5+ is the primary direct substitute, maintaining the same 24-SOIC package footprint with compatible voltage supply (4.5V ~ 5.5V), parallel interface, and equivalent feature set including alarm, NVSRAM, and square wave output.

Category 2: Enhanced Memory Alternatives (24-SOIC Package) DS17285S-3+T&R provides 24-SOIC package compatibility with expanded memory (2KB vs 114B) and lower supply voltage range (2.7V ~ 3.7V), suitable for applications requiring additional storage capacity.

Category 3: Through-Hole Package Alternatives (24-DIP) DS17487-5+ and DS1687-5+ offer through-hole mounting in 24-DIP modules with equivalent feature sets and voltage specifications, applicable for legacy board designs or applications requiring through-hole components.

Category 4: High-Capacity PowerCap Module Alternatives (34-PowerCap) DS1556WP-120IND+, DS1557WP-120IND+, DS1747P-70IND+, and DS1747WP-120+ provide significantly expanded memory (128KB to 512KB) in 34-PowerCap surface mount modules with parallel interface, suitable for applications requiring extended data storage with RTC functionality.

Category 5: Extended Temperature Range Alternatives DS1687-5IND+ and DS1747P-70IND+ extend operating temperature to -40°C ~ 85°C, applicable for industrial and automotive environments.

Parameter Comparison

Parameter	BQ4285S-SB2TR	DS1685E-5+	DS17285S-3+T&R	DS17487-5+	DS1687-5+	DS1747WP-120+
Manufacturer	Texas Instruments	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim
Type	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar
Package / Case	24-SOIC	24-TSSOP	24-SOIC	24-DIP Module	24-DIP Module	34-PowerCap Module
Memory Size	114B	242B	2KB	4KB	242B	512KB
Interface	Parallel	Parallel	Parallel	Parallel	Parallel	Parallel
Voltage - Supply	4.5V ~ 5.5V	4.5V ~ 5.5V	2.7V ~ 3.7V	4.5V ~ 5.5V	4.5V ~ 5.5V	2.97V ~ 3.63V
Voltage - Supply, Battery	2.5V ~ 4V	2.5V ~ 3.7V	2.5V ~ 3.7V	2.5V ~ 3.7V	2.5V ~ 3.7V	3V
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (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	YY-MM-DD-dd	YY-MM-DD-dd
Operating Temperature	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Through Hole	Through Hole	Surface Mount
Features	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output	Alarm, NVSRAM, Square Wave Output, Y2K	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output	Alarm, NVSRAM, Square Wave Output, Y2K	Leap Year, NVSRAM, Y2K
Product Status	Obsolete	Active	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Same Package Footprint): DS1685E-5+ is the recommended substitute for applications requiring identical 24-SOIC surface mount package compatibility. This part maintains active product status, ROHS3 compliance, and equivalent feature set with the original BQ4285S-SB2TR.

For Enhanced Memory Requirements: DS17285S-3+T&R provides 24-SOIC package compatibility with expanded 2KB memory capacity. This part operates at lower supply voltage (2.7V ~ 3.7V) and maintains active product status with ROHS3 compliance.

For Through-Hole Applications: DS17487-5+ and DS1687-5+ offer 24-DIP module packages for legacy board designs. Both maintain active product status and ROHS3 compliance with equivalent feature sets.

For Extended Temperature Range: DS1687-5IND+ extends operating temperature to -40°C ~ 85°C while maintaining 24-DIP package compatibility, suitable for industrial environments.

For High-Capacity Storage: DS1747WP-120+ provides 512KB memory in 34-PowerCap surface mount module with active product status and ROHS3 compliance. This option is applicable when expanded data storage is required alongside RTC functionality.

All recommended substitutes maintain ROHS3 compliance and active product status, ensuring long-term availability and regulatory compliance.

Frequently Asked Questions (FAQ)

Q: Can DS1685E-5+ directly replace BQ4285S-SB2TR on existing PCBs? A: DS1685E-5+ uses 24-TSSOP package while BQ4285S-SB2TR uses 24-SOIC package. Although both are 24-pin surface mount packages with similar pin pitch, they have different footprints and are not pin-compatible for direct PCB replacement without layout modification. DS17285S-3+T&R maintains the identical 24-SOIC footprint for direct replacement.

Q: What is the primary difference between DS1685E-5+ and DS17285S-3+T&R? A: DS1685E-5+ uses 24-TSSOP package with 242B memory and 4.5V ~ 5.5V supply voltage. DS17285S-3+T&R uses 24-SOIC package with 2KB memory and 2.7V ~ 3.7V supply voltage. DS17285S-3+T&R provides identical package footprint to the original BQ4285S-SB2TR.

Q: Are the PowerCap module alternatives (DS1556WP-120IND+, DS1557WP-120IND+, DS1747WP-120+) compatible with existing BQ4285S-SB2TR designs? A: No. PowerCap modules use 34-pin packages versus the original 24-pin SOIC package. These alternatives require PCB redesign and are applicable only for new designs requiring high-capacity memory storage with RTC functionality.

Q: What is the significance of the 12/24 hour time format difference in DS1747WP-120+? A: DS1747WP-120+ supports only 24-hour time format, while BQ4285S-SB2TR supports both 12-hour and 24-hour formats. Applications requiring 12-hour format operation must select alternatives that explicitly support this feature, such as DS1685E-5+, DS17285S-3+T&R, or DS17487-5+.

Q: Which substitute parts support extended industrial temperature range? A: DS1687-5IND+ and DS1747P-70IND+ extend operating temperature to -40°C ~ 85°C. Standard alternatives operate within 0°C ~ 70°C range. Extended temperature variants are required for industrial and automotive applications.

Q: Are all substitute parts ROHS3 compliant? A: Yes. All recommended substitute parts maintain ROHS3 compliance status, ensuring regulatory compliance equivalent to the original BQ4285S-SB2TR.

Q: What packaging options are available for through-hole applications? A: DS17487-5+ and DS1687-5+ provide 24-DIP module packages for through-hole mounting. DS1687-5IND+ offers the same 24-DIP package with extended temperature range (-40°C ~ 85°C).

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