DS32B35-33# Real Time Clock (RTC) IC Equivalent & Substitute Parts

Part Overview

The DS32B35-33# is a Real Time Clock (RTC) IC manufactured by Analog Devices Inc./Maxim Integrated, designed for clock/calendar applications with I2C 2-Wire Serial interface. This device features 2KB FRAM memory, alarm functionality, leap year support, and square wave output capability. The part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	DS32B35-33#
Manufacturer	Analog Devices Inc./Maxim Integrated
Product Status	Obsolete
Type	Clock/Calendar
Memory Size	2KB
Interface	I2C, 2-Wire Serial
Voltage Supply Range	2.7V ~ 3.63V
Battery Supply Range	2.3V ~ 3.6V
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Package	20-SOIC (0.295", 7.50mm Width)
Operating Temperature	0°C ~ 70°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the DS32B35-33# is determined by the following critical parameters:

Interface Compatibility: All substitute parts must support I2C 2-Wire Serial communication
Time/Date Format: Substitutes must support HH:MM:SS (12/24 hr) and YY-MM-DD-dd formats
Voltage Supply Range: Operating voltage must overlap with or exceed the original 2.7V ~ 3.63V range
Functional Features: Core features include clock/calendar functionality with alarm and leap year support
Compliance: All parts must maintain ROHS3 compliance and EAR99 classification

Substitute parts are grouped into two categories based on package compatibility and memory architecture:

Category A - Compact Package Alternatives (8-SOIC/8-MSOP): Parts with reduced pin count and lower memory capacity, suitable for space-constrained applications.

Category B - Enhanced Feature Alternatives (10-SMD Module/16-QFN): Parts with integrated modules or higher memory capacity, offering extended functionality.

Category C - Standard Package Alternatives (18-SOX): Parts maintaining larger package formats with integrated crystal support.

Parameter Comparison

Part Number	Manufacturer	Memory Size	Package	Voltage Supply	Battery Supply	Current (Max)	Temp Range	Status
DS32B35-33#	Analog Devices/Maxim	2KB	20-SOIC	2.7V ~ 3.63V	2.3V ~ 3.6V	110µA @ 3.63V	0°C ~ 70°C	Obsolete
1338-31DCGI	Renesas Electronics	56B	8-SOIC	3.3V ~ 5.5V	1.3V ~ 3.7V	5µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Active
AB-RTCMC-32.768KHZ-EOZ9-S3-DBT	Abracon LLC	8B	10-SMD Module	1.4V ~ 5.5V	1.4V ~ 5.5V	1.5µA ~ 2.2µA @ 1.4V ~ 5V	-40°C ~ 85°C	Active
AB1805-T3	Abracon LLC	256B	16-VFQFN	1.7V ~ 3.6V	1.5V ~ 3.6V	0.17µA ~ 0.22µA @ 1.8V ~ 3V	-40°C ~ 85°C	Active
ISL12022IBZ	Renesas Electronics	128B	8-SOIC	2.7V ~ 5.5V	1.8V ~ 5.5V	14µA ~ 15µA @ 3V ~ 5V	-40°C ~ 85°C	Active
ISL12057IUZ	Renesas Electronics	—	8-MSOP	1.8V ~ 3.6V	—	0.65µA @ 1.8V	-40°C ~ 85°C	Active
ISL12058IUZ	Renesas Electronics	—	8-MSOP	1.8V ~ 3.6V	—	0.65µA @ 1.8V	-40°C ~ 85°C	Active
M41T00M6F	STMicroelectronics	—	8-SOIC	2V ~ 5.5V	2.5V ~ 4.6V	70µA @ 2V ~ 5.5V	-40°C ~ 85°C	Active
M41T82RM6F	STMicroelectronics	7B	8-SOIC	2.7V ~ 5.5V	2V ~ 5.5V	10µA @ 5.5V	-40°C ~ 85°C	Active
M41T83ZMY6F	STMicroelectronics	7B	18-SOX	2.38V ~ 5.5V	2V ~ 5.5V	10µA @ 5.5V	-40°C ~ 85°C	Active
MCP79400T-I/MS	Microchip Technology	64B	8-MSOP	1.8V ~ 5.5V	1.3V ~ 5.5V	1.2µA (Typ) @ 3.3V	-40°C ~ 85°C	Active

Engineering Selection Recommendations

For Direct Voltage Range Compatibility (2.7V ~ 3.63V)

ISL12022IBZ and M41T82RM6F provide the closest voltage supply overlap with the original DS32B35-33#. Both parts support the 2.7V minimum supply requirement and maintain ROHS3 compliance. ISL12022IBZ operates to 5.5V maximum, while M41T82RM6F extends to 5.5V, offering broader system integration flexibility.

For Low-Power Applications

AB1805-T3 and ISL12057IUZ/ISL12058IUZ deliver significantly reduced timekeeping current consumption (0.17µA ~ 0.65µA) compared to the original part (110µA). These options are suitable for battery-backed applications requiring extended operational life.

For Package Footprint Preservation

M41T83ZMY6F maintains an 18-pin package format similar to the original 20-SOIC, facilitating minimal PCB redesign. This part includes integrated crystal support and maintains all core clock/calendar functionality with alarm and watchdog timer features.

For Active Production Status

All listed substitute parts maintain active product status with established supply chains. ISL12022IBZ, M41T82RM6F, and MCP79400T-I/MS represent the most widely available alternatives across multiple distributors.

Compliance Verification

All substitute parts maintain ROHS3 compliance, REACH unaffected status, and EAR99 classification, matching the regulatory profile of the original DS32B35-33#.

Frequently Asked Questions (FAQ)

Q: Can I directly replace DS32B35-33# with a smaller package alternative?

A: Direct pin-for-pin replacement is not possible due to package differences. The original DS32B35-33# uses 20-SOIC packaging. Alternatives such as 8-SOIC (ISL12022IBZ, M41T00M6F, M41T82RM6F) or 8-MSOP (ISL12057IUZ, ISL12058IUZ, MCP79400T-I/MS) require PCB redesign. The 18-SOX package (M41T83ZMY6F) provides closer pin compatibility with integrated crystal support.

Q: What is the minimum voltage requirement for substitute selection?

A: The original DS32B35-33# operates from 2.7V minimum. Substitute parts maintaining this specification include ISL12022IBZ (2.7V ~ 5.5V) and M41T82RM6F (2.7V ~ 5.5V). Parts with lower minimum voltage (1.8V or 1.4V) offer extended operating range but require verification of system-level voltage distribution.

Q: Are all substitute parts I2C compatible with the original design?

A: Yes. All listed substitute parts support I2C 2-Wire Serial interface and maintain HH:MM:SS (12/24 hr) and YY-MM-DD-dd time/date formats. Software compatibility depends on register map alignment, which must be verified against specific application firmware.

Q: Which substitute offers the best power efficiency?

A: AB1805-T3 provides the lowest timekeeping current at 0.17µA ~ 0.22µA @ 1.8V ~ 3V, representing a 500x reduction compared to the original DS32B35-33# (110µA @ 3.63V). ISL12057IUZ and ISL12058IUZ offer 0.65µA @ 1.8V, providing significant power savings for battery-backed applications.

Q: What memory capacity differences exist among substitutes?

A: The original DS32B35-33# provides 2KB FRAM memory. Substitute parts vary: AB-RTCMC-32.768KHZ-EOZ9-S3-DBT (8B), 1338-31DCGI (56B), MCP79400T-I/MS (64B), ISL12022IBZ (128B), AB1805-T3 (256B). Applications requiring large data storage must select accordingly; most clock/calendar functions operate with minimal memory requirements.

Q: Is the 18-SOX package (M41T83ZMY6F) a suitable alternative for space-constrained designs?

A: M41T83ZMY6F maintains an 18-pin format with integrated crystal, reducing external component count. This package is suitable for applications where the original 20-SOIC footprint can be accommodated with minor layout adjustments. The integrated crystal eliminates external oscillator requirements, potentially reducing overall board area.

Q: Do all substitutes support alarm and leap year functions?

A: Alarm functionality is present in AB-RTCMC-32.768KHZ-EOZ9-S3-DBT, AB1805-T3, ISL12022IBZ, M41T82RM6F, M41T83ZMY6F, and MCP79400T-I/MS. Leap year support is universal across all listed parts. M41T00M6F and ISL12057IUZ/ISL12058IUZ support leap year but lack alarm functionality.

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