DS1338U-33 Real Time Clock IC - Equivalent & Substitute Parts

Part Overview

The DS1338U-33 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, manufactured by Analog Devices Inc./Maxim Integrated. This device integrates a 56-byte I2C interface for 2-wire serial communication, supporting both 12/24-hour time formats and calendar functions with leap year capability. The DS1338U-33 is classified as obsolete, necessitating identification of active substitute components for new designs and production continuity. Substitute parts must maintain functional equivalence in I2C protocol, time/date format support, operating temperature range, and supply voltage specifications while accommodating packaging and feature variations.

Key Parameters

Parameter	DS1338U-33 Specification
Manufacturer	Analog Devices Inc./Maxim Integrated
Product Status	Obsolete
Type	Clock/Calendar
Memory Size	56B
Interface	I2C, 2-Wire Serial
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Voltage - Supply	3V ~ 5.5V
Voltage - Supply, Battery	1.3V ~ 3.7V
Current - Timekeeping (Max)	125µA ~ 200µA @ 3.63V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
Features	Leap Year, NVSRAM, Square Wave Output
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution logic for the DS1338U-33 is based on the following critical parameters:

Primary Compatibility Criteria:

I2C/2-Wire Serial interface protocol
Time format support: HH:MM:SS with 12/24-hour capability
Date format support: YY-MM-DD-dd
Operating temperature range: -40°C ~ 85°C minimum
Supply voltage overlap: 3V ~ 5.5V range or compatible subset
Surface mount packaging

Substitution Categories:

Direct Package Match (8-TSSOP/8-MSOP): ISL12058IUZ-T maintains identical package geometry and pinout compatibility, enabling direct board-level replacement with minimal design modification.

Functional Equivalents with Package Variation (8-SOIC): ISL12022IBZ-T7A, ISL12026AIBZ, ISL12058IBZ-T, BQ32002D, and M41T80M6F provide equivalent RTC functionality with I2C interface and compatible electrical specifications but require PCB layout adjustment due to different package footprint (8-SOIC vs. 8-TSSOP).

Enhanced Feature Variants (16-Pin Packages): AB0805-T3, M41T00AUDD1F, and M41T83SQA6F offer expanded memory, additional features (alarm, watchdog timer, trickle-charger), and improved power efficiency but require board redesign for 16-pin package integration.

Active Status Requirement: All listed substitutes maintain active product status with RoHS3 compliance, addressing obsolescence and regulatory requirements of the original DS1338U-33.

Parameter Comparison

Part Number	Manufacturer	Package	Interface	Time Format	Date Format	Supply Voltage	Battery Voltage	Timekeeping Current (Max)	Operating Temp	Product Status	RoHS Status
DS1338U-33	Analog Devices/Maxim	8-TSSOP/8-MSOP	I2C, 2-Wire	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	3V ~ 5.5V	1.3V ~ 3.7V	125µA ~ 200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Obsolete	RoHS non-compliant
DS1338U-33+	Analog Devices/Maxim	8-TSSOP/8-MSOP	I2C, 2-Wire	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	3V ~ 5.5V	1.3V ~ 3.7V	125µA ~ 200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
ISL12058IUZ-T	Renesas Electronics	8-TSSOP/8-MSOP	I2C, 2-Wire	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	1.8V ~ 3.6V	—	0.65µA @ 1.8V	-40°C ~ 85°C	Active	ROHS3 Compliant
ISL12022IBZ-T7A	Renesas Electronics	8-SOIC	I2C, 2-Wire	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	2.7V ~ 5.5V	1.8V ~ 5.5V	14µA ~ 15µA @ 3V ~ 5V	-40°C ~ 85°C	Active	ROHS3 Compliant
ISL12026AIBZ	Renesas Electronics	8-SOIC	I2C, 2-Wire	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	2.7V ~ 5.5V	1.8V ~ 5.5V	10µA ~ 20µA @ 2.7V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
ISL12058IBZ-T	Renesas Electronics	8-SOIC	I2C, 2-Wire	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	1.8V ~ 3.6V	—	0.65µA @ 1.8V	-40°C ~ 85°C	Active	ROHS3 Compliant
BQ32002D	Texas Instruments	8-SOIC	I2C, 2-Wire	HH:MM:SS (24 hr)	YY-MM-DD-dd	3V ~ 3.6V	1.4V ~ 3.6V	200µA @ 3.3V	-40°C ~ 85°C	Active	ROHS3 Compliant
M41T80M6F	STMicroelectronics	8-SOIC	I2C, 2-Wire	HH:MM:SS:hh (24 hr)	YY-MM-DD-dd	2V ~ 5.5V	—	2.4µA ~ 31µA @ 2V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
AB0805-T3	Abracon LLC	16-VFQFN	I2C, 2-Wire	HH:MM:SS:hh	YY-MM-DD-dd	1.7V ~ 3.6V	1.5V ~ 3.6V	0.17µA ~ 0.22µA @ 1.8V ~ 3V	-40°C ~ 85°C	Active	ROHS3 Compliant
M41T00AUDD1F	STMicroelectronics	16-VFDFN	I2C, 2-Wire	HH:MM:SS (24 hr)	YY-MM-DD-dd	3V ~ 3.6V	1.7V ~ 3.6V	14.3mA @ 3V ~ 3.6V	0°C ~ 70°C	Active	ROHS3 Compliant
M41T83SQA6F	STMicroelectronics	16-VQFN	I2C, 2-Wire	HH:MM:SS:hh (24 hr)	YY-MM-DD-dd	3V ~ 5.5V	2V ~ 5.5V	10µA @ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant

Engineering Selection Recommendations

Direct Replacement (Minimal Design Change): DS1338U-33+ is the primary substitute, offering identical electrical specifications, package geometry, and pinout to the obsolete DS1338U-33. The transition from RoHS non-compliant to ROHS3 compliant status addresses regulatory requirements without functional modification. ISL12058IUZ-T provides equivalent package compatibility with superior power efficiency (0.65µA timekeeping current vs. 125µA ~ 200µA), though supply voltage range is narrower (1.8V ~ 3.6V vs. 3V ~ 5.5V).

Package-Compatible Alternatives (8-SOIC): ISL12022IBZ-T7A, ISL12026AIBZ, ISL12058IBZ-T, and M41T80M6F maintain I2C protocol and time/date format compatibility but require PCB footprint redesign. These options provide active product status and RoHS3 compliance. ISL12026AIBZ offers the lowest timekeeping current (10µA ~ 20µA) among 8-SOIC variants. BQ32002D is suitable for 3V ~ 3.6V supply applications with 24-hour time format support.

Enhanced Feature Variants (16-Pin Packages): AB0805-T3, M41T00AUDD1F, and M41T83SQA6F provide expanded functionality including alarm, watchdog timer, and trickle-charger capabilities. AB0805-T3 delivers the lowest power consumption (0.17µA ~ 0.22µA) and widest battery voltage range (1.5V ~ 3.6V). M41T83SQA6F maintains the full -40°C ~ 85°C operating range with 3V ~ 5.5V supply compatibility. M41T00AUDD1F operates within 0°C ~ 70°C range, limiting use in extended temperature applications.

Compliance and Availability: All recommended substitutes maintain active product status and ROHS3 compliance, eliminating obsolescence risk and satisfying regulatory requirements. Inventory availability ranges from 952 to 70,300 units across substitute options, supporting production continuity.

Frequently Asked Questions (FAQ)

Q: Can DS1338U-33+ be used as a direct drop-in replacement for DS1338U-33? A: Yes. DS1338U-33+ maintains identical package (8-TSSOP/8-MSOP), pinout, supply voltage (3V ~ 5.5V), battery voltage (1.3V ~ 3.7V), time/date format support, and operating temperature range (-40°C ~ 85°C). The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant). No PCB or firmware modifications are required.

Q: What is the key difference between ISL12058IUZ-T and DS1338U-33? A: Both use identical 8-TSSOP/8-MSOP packaging and I2C interface with 12/24-hour time format and YY-MM-DD-dd date format support. ISL12058IUZ-T offers significantly lower timekeeping current (0.65µA @ 1.8V vs. 125µA ~ 200µA @ 3.63V ~ 5.5V), reducing power consumption in battery-backed applications. However, supply voltage range is narrower (1.8V ~ 3.6V vs. 3V ~ 5.5V), requiring verification for 5V-only systems.

Q: Why do 8-SOIC alternatives require PCB redesign? A: The 8-SOIC package (0.154", 3.90mm width) has different physical dimensions and pin spacing compared to the 8-TSSOP/8-MSOP package (0.118", 3.00mm width). PCB footprint, trace routing, and component placement must be modified to accommodate the larger package. Pinout compatibility is maintained, but board layout changes are mandatory.

Q: Are 16-pin package alternatives suitable for existing DS1338U-33 designs? A: No. 16-pin packages (AB0805-T3, M41T00AUDD1F, M41T83SQA6F) require complete PCB redesign due to increased pin count and different package geometry. These alternatives are recommended for new designs requiring enhanced features (alarm, watchdog timer, trickle-charger) or improved power efficiency. Existing designs should prioritize 8-pin package substitutes.

Q: Which substitute offers the best power efficiency for battery-backed timekeeping? A: AB0805-T3 provides the lowest timekeeping current (0.17µA ~ 0.22µA @ 1.8V ~ 3V) among all substitutes, making it optimal for ultra-low-power battery-backed applications. ISL12058IUZ-T and ISL12058IBZ-T follow with 0.65µA @ 1.8V. These options are suitable for designs prioritizing extended battery life.

Q: What is the operating temperature limitation of M41T00AUDD1F? A: M41T00AUDD1F operates within 0°C ~ 70°C, which is narrower than the DS1338U-33 range (-40°C ~ 85°C). This device is unsuitable for applications requiring extended temperature operation below 0°C or above 70°C. Alternative substitutes (ISL12022IBZ-T7A, ISL12026AIBZ, M41T80M6F, M41T83SQA6F) maintain the full -40°C ~ 85°C range.

Q: Are all substitutes RoHS3 compliant? A: Yes. All listed substitutes maintain ROHS3 compliance. The original DS1338U-33 is RoHS non-compliant, making substitution necessary for designs subject to RoHS regulations or customer requirements.

Q: Can BQ32002D replace DS1338U-33 in 5V-only systems? A: No. BQ32002D supply voltage range is 3V ~ 3.6V, which does not accommodate 5V operation. This device is limited to 3.3V systems. For 5V-compatible substitutes, select DS1338U-33+, ISL12022IBZ-T7A, ISL12026AIBZ, M41T80M6F, or M41T83SQA6F.

Q: What is the memory size difference between DS1338U-33 and AB0805-T3? A: DS1338U-33 provides 56 bytes of NVSRAM. AB0805-T3 offers 256 bytes of memory, providing expanded storage for user data and configuration parameters. This additional memory capacity may benefit applications requiring extended data logging or parameter storage without external memory components.

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