BQ3285ESSTR Equivalent & Substitute Parts

Part Overview

The BQ3285ESSTR is a Real Time Clock (RTC) IC with integrated Clock/Calendar functionality, manufactured by Texas Instruments. This device provides 242 bytes of parallel-accessible memory with timekeeping capabilities including alarm, daylight savings, leap year support, and non-volatile static RAM (NVSRAM). The BQ3285ESSTR is classified as obsolete, making equivalent and substitute parts necessary for ongoing system support and new design implementations.

Key Parameters

Parameter	BQ3285ESSTR
Manufacturer	Texas Instruments
Product Status	Obsolete
Type	Clock/Calendar
Memory Size	242 Bytes
Interface	Parallel
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Voltage - Supply	4.5V ~ 5.5V
Voltage - Supply, Battery	2.5V ~ 4V
Current - Timekeeping (Max)	300µA @ 5V
Operating Temperature	0°C ~ 70°C
Mounting Type	Surface Mount
Package / Case	24-SSOP (0.154", 3.90mm Width)
Features	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the BQ3285ESSTR is determined by the following critical parameters:

Interface Type: Parallel interface requirement
Time/Date Format: HH:MM:SS (12/24 hr) and YY-MM-DD-dd support
Memory Capacity: Minimum 242 bytes for functional equivalence
Supply Voltage Compatibility: 4.5V ~ 5.5V primary supply range
Mounting Type: Surface mount or through-hole alternatives
Package Compatibility: Pin count and physical dimensions
Feature Set: Alarm, daylight savings, leap year, and NVSRAM support

Substitute parts are grouped into two categories:

Category 1 - Surface Mount Direct Substitutes (24-pin packages):

DS17285S-5+T&R: 24-SOIC package, active status, enhanced memory (2KB)

Category 2 - Through-Hole Alternatives (24-32 pin packages):

DS17487-3+: 24-DIP module, active status, 4KB memory, full feature set
DS1746-70+: 32-DIP module, active status, 128KB memory
DS1746W-120IND+: 32-DIP module, active status, 128KB memory, extended temperature range
DS1747W-120+: 32-DIP module, active status, 512KB memory
M48T08-100PC1: 28-DIP module, active status, Timekeeper® series
M48T35Y-70MH1F: 28-SOP surface mount, active status, Timekeeper® series
M48T58Y-70PC1: 28-DIP module, active status, Timekeeper® series

Parameter Comparison

Parameter	BQ3285ESSTR	DS17285S-5+T&R	DS17487-3+	DS1746-70+	DS1746W-120IND+	DS1747W-120+	M48T08-100PC1	M48T35Y-70MH1F	M48T58Y-70PC1
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	STMicroelectronics	STMicroelectronics	STMicroelectronics
Product Status	Obsolete	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
Memory Size	242 Bytes	2KB	4KB	128KB	128KB	512KB	—	—	—
Interface	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)
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
Voltage - Supply	4.5V ~ 5.5V	4.5V ~ 5.5V	2.7V ~ 3.7V	4.5V ~ 5.5V	2.97V ~ 3.63V	2.97V ~ 3.63V	4.75V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V
Voltage - Supply, Battery	2.5V ~ 4V	2.5V ~ 3.7V	2.5V ~ 3.7V	—	—	—	—	—	—
Current - Timekeeping (Max)	300µA @ 5V	3mA @ 4.5V ~ 5.5V	2mA @ 2.7V ~ 3.7V	4mA @ 5V	2mA @ 3.3V	2mA @ 3.3V	3mA @ 4.7V ~ 5.5V	2mA @ 4.75V ~ 5.5V	3mA @ 4.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	-40°C ~ 85°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C
Mounting Type	Surface Mount	Surface Mount	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Surface Mount	Through Hole
Package / Case	24-SSOP (0.154", 3.90mm Width)	24-SOIC (0.295", 7.50mm Width)	24-DIP Module (0.600", 15.24mm)	32-DIP Module (0.600", 15.24mm)	32-DIP Module (0.600", 15.24mm)	32-DIP Module (0.600", 15.24mm)	28-DIP Module (0.600", 15.24mm)	28-SOP (0.350", 8.89mm Width)	28-DIP Module (0.600", 15.24mm)
Features	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output	Alarm, Daylight Savings, Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Y2K	Leap Year, NVSRAM, Y2K	Leap Year, NVSRAM, Y2K	Leap Year, Watchdog Timer	Leap Year	Leap Year
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Surface Mount Applications (Direct Package Compatibility):

DS17285S-5+T&R is the primary surface mount substitute for BQ3285ESSTR. Both devices use surface mount packaging and maintain parallel interface compatibility. DS17285S-5+T&R is active status with ROHS3 compliance. The 24-SOIC package is slightly larger than the 24-SSOP but maintains the same pin count and functional interface. Memory capacity increases to 2KB, providing enhanced storage capability.

M48T35Y-70MH1F offers an alternative surface mount option in 28-SOP package with Timekeeper® series designation. This device is active status and ROHS3 compliant. The different pin count (28 vs. 24) requires PCB redesign but provides proven reliability in the Timekeeper® product line.

For Through-Hole Applications:

DS17487-3+ provides the closest functional match among through-hole options, maintaining 24-pin DIP configuration with full feature set including alarm and daylight savings. This device is active status with ROHS3 compliance and operates within compatible voltage ranges.

DS1746-70+ and DS1746W-120IND+ offer 32-DIP packages with significantly expanded memory (128KB). DS1746W-120IND+ extends operating temperature to -40°C ~ 85°C, suitable for industrial applications. Both are active status with ROHS3 compliance.

DS1747W-120+ provides maximum memory capacity (512KB) in 32-DIP package with active status and ROHS3 compliance. Operating voltage range is 2.97V ~ 3.63V, requiring system voltage compatibility verification.

M48T08-100PC1, M48T58Y-70PC1 represent STMicroelectronics Timekeeper® series alternatives in 28-DIP packages. Both are active status with ROHS3 compliance and proven field reliability.

Compliance Considerations:

All substitute parts maintain ROHS3 compliance matching the original BQ3285ESSTR. All substitute parts are active status, ensuring long-term availability and manufacturing support.

Frequently Asked Questions (FAQ)

Q: Can DS17285S-5+T&R directly replace BQ3285ESSTR on existing PCBs?

A: DS17285S-5+T&R uses 24-SOIC package versus BQ3285ESSTR's 24-SSOP package. While pin count is identical, physical dimensions differ. The 24-SOIC package is wider (0.295" vs. 0.154"), requiring PCB footprint modification. Electrical interface and functionality are compatible.

Q: What is the primary advantage of DS17487-3+ as a substitute?

A: DS17487-3+ maintains 24-pin DIP configuration with full feature set (alarm, daylight savings, leap year, NVSRAM, square wave output) matching BQ3285ESSTR capabilities. It is active status with proven availability. Through-hole mounting eliminates surface mount soldering requirements.

Q: Why do DS1746 and DS1747 series devices have different voltage requirements?

A: DS1746-70+ operates at 4.5V ~ 5.5V (5V logic), while DS1746W-120IND+ and DS1747W-120+ operate at 2.97V ~ 3.63V (3.3V logic). System voltage compatibility must be verified before selection. These represent different product variants optimized for specific voltage domains.

Q: Are Timekeeper® series devices (M48T08, M48T35, M48T58) functionally equivalent to BQ3285ESSTR?

A: Timekeeper® series devices provide parallel RTC functionality with clock/calendar support and leap year capability. Feature sets differ: M48T08 includes watchdog timer; M48T35 and M48T58 provide basic leap year support. All are active status with ROHS3 compliance. Pin counts and package types differ from BQ3285ESSTR, requiring PCB redesign.

Q: What memory capacity should be selected for new designs?

A: BQ3285ESSTR provides 242 bytes. Substitute options range from 2KB (DS17285S-5+T&R) to 512KB (DS1747W-120+). Selection depends on application data storage requirements. Larger memory capacity provides design flexibility for future feature expansion without component substitution.

Q: Is battery backup voltage compatibility critical for substitution?

A: Yes. BQ3285ESSTR supports 2.5V ~ 4V battery backup. DS17285S-5+T&R and DS17487-3+ support 2.5V ~ 3.7V, requiring verification of existing battery voltage. DS1746, DS1747, and M48T series do not specify battery backup voltage, indicating no battery backup support in those variants.

Q: Can through-hole devices replace surface mount BQ3285ESSTR in existing designs?

A: Through-hole substitution requires PCB redesign. Existing surface mount footprints cannot accommodate through-hole packages. New PCB layout is necessary. Through-hole alternatives are suitable for new designs or board revisions where layout flexibility exists.

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