DS1340U-3 Real Time Clock IC Equivalent & Substitute Parts

Part Overview

The DS1340U-3 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, featuring I2C 2-Wire Serial interface in 8-TSSOP/8-MSOP packaging. This component is classified as Obsolete by the manufacturer, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The DS1340U-3 provides timekeeping with leap year support and trickle-charger functionality across a 2.7V to 5.5V supply range with battery backup capability from 1.3V to 3.7V.

Key Parameters

Parameter	DS1340U-3 Specification
Manufacturer	Analog Devices Inc./Maxim Integrated
Product Status	Obsolete
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Package / Case	8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
Voltage - Supply	2.7V ~ 5.5V
Voltage - Supply, Battery	1.3V ~ 3.7V
Current - Timekeeping (Max)	125µA @ 3.3V
Time Format	HH:MM:SS (24 hr)
Date Format	YY-MM-DD-dd
Operating Temperature	-40°C ~ 85°C
Features	Leap Year, Trickle-Charger
Mounting Type	Surface Mount
RoHS Status	RoHS non-compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the DS1340U-3 is determined by the following critical parameters:

Primary Compatibility Criteria:

I2C 2-Wire Serial interface (mandatory for protocol compatibility)
Operating temperature range of -40°C to 85°C (standard industrial range)
Surface mount technology with compatible package footprint
Supply voltage range encompassing 2.7V to 5.5V
Time format supporting 24-hour operation
Date format supporting YY-MM-DD-dd structure

Substitution Categories:

Category 1: Direct Pin-Compatible Substitutes (8-pin TSSOP/MSOP packages)

DS1340U-3+ (Analog Devices Inc./Maxim Integrated) - Active product status, identical electrical specifications, RoHS3 compliant
ISL12026AIVZ-T (Renesas Electronics Corporation) - 8-TSSOP package, I2C interface, compatible voltage and temperature ranges

Category 2: Functional Equivalents (8-pin SOIC packages)

ISL12008IB8Z-T (Renesas Electronics Corporation) - 8-SOIC package, I2C interface, compatible electrical specifications
1337GDCGI8 (Renesas Electronics Corporation) - 8-SOIC package, I2C interface, extended supply voltage range
M41T0M6F (STMicroelectronics) - 8-SOIC package, I2C interface, compatible specifications
M41T82RM6F (STMicroelectronics) - 8-SOIC package with enhanced features (alarm, watchdog timer)

Category 3: Enhanced Feature Substitutes (larger packages with additional memory/features)

AB-RTCMC-32.768KHZ-EOZ9-S3-DBT (Abracon LLC) - 10-SMD Module, integrated crystal, 8B memory, extended feature set
ISL12022MIBZ (Renesas Electronics Corporation) - 20-SOIC package, 128B SRAM, enhanced alarm and daylight savings features
M41ST87WSS6F (STMicroelectronics) - 20-SSOP package, 128B NVSRAM, supervisor and watchdog timer functions
M41T56M6F (STMicroelectronics) - 8-SOIC package, 56B NVSRAM, leap year and NVSRAM support

Parameter Comparison

Part Number	Manufacturer	Package	Interface	Supply Voltage	Battery Voltage	Timekeeping Current	Time Format	Operating Temp	Product Status	RoHS Status
DS1340U-3	Analog Devices/Maxim	8-TSSOP/MSOP	I2C, 2-Wire	2.7V ~ 5.5V	1.3V ~ 3.7V	125µA @ 3.3V	HH:MM:SS (24 hr)	-40°C ~ 85°C	Obsolete	Non-compliant
DS1340U-3+	Analog Devices/Maxim	8-TSSOP/MSOP	I2C, 2-Wire	2.7V ~ 5.5V	1.3V ~ 3.7V	125µA @ 3.3V	HH:MM:SS (24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
ISL12026AIVZ-T	Renesas Electronics	8-TSSOP	I2C, 2-Wire	2.7V ~ 5.5V	1.8V ~ 5.5V	10µA ~ 20µA @ 2.7V ~ 5.5V	HH:MM:SS (12/24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
ISL12008IB8Z-T	Renesas Electronics	8-SOIC	I2C, 2-Wire	2.7V ~ 5.5V	1.8V ~ 5.5V	4µA ~ 6µA @ 3V ~ 5V	HH:MM:SS:hh (24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
1337GDCGI8	Renesas Electronics	8-SOIC	I2C, 2-Wire	1.8V ~ 5.5V	N/A	0.6µA @ 1.3V ~ 1.8V	HH:MM:SS (12/24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
M41T0M6F	STMicroelectronics	8-SOIC	I2C, 2-Wire	2V ~ 5.5V	N/A	1.2µA ~ 31µA @ 3V ~ 5.5V	HH:MM:SS	-40°C ~ 85°C	Active	RoHS3 Compliant
M41T82RM6F	STMicroelectronics	8-SOIC	I2C, 2-Wire	2.7V ~ 5.5V	2V ~ 5.5V	10µA @ 5.5V	HH:MM:SS:hh (24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
M41T56M6F	STMicroelectronics	8-SOIC	I2C, 2-Wire	4.5V ~ 5.5V	2.5V ~ 4.6V	100µA (Typ) @ 4.5V ~ 5.5V	HH:MM:SS (24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
ISL12022MIBZ	Renesas Electronics	20-SOIC	I2C, 2-Wire	2.7V ~ 5.5V	1.8V ~ 5.5V	14µA ~ 15µA @ 3V ~ 5V	HH:MM:SS (12/24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
M41ST87WSS6F	STMicroelectronics	20-SSOP	I2C, 2-Wire	2.7V ~ 3.6V	2.5V ~ 3.6V	0.5mA @ 2.7V ~ 3.6V	HH:MM:SS:hh (24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant
AB-RTCMC-32.768KHZ-EOZ9-S3-DBT	Abracon LLC	10-SMD Module	I2C, 2-Wire	1.4V ~ 5.5V	1.4V ~ 5.5V	1.5µA ~ 2.2µA @ 1.4V ~ 5V	HH:MM:SS (12/24 hr)	-40°C ~ 85°C	Active	RoHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Pin-Compatible, No PCB Redesign):

DS1340U-3+ is the primary recommendation. It maintains identical electrical specifications and package footprint as the obsolete DS1340U-3 while offering Active product status and RoHS3 compliance. This part requires no circuit modifications and provides the most straightforward migration path.

For New Designs with Package Flexibility:

ISL12026AIVZ-T offers an 8-TSSOP package compatible with the original footprint while providing Active status and RoHS3 compliance. The part supports both 12-hour and 24-hour time formats and operates across the required temperature range.

For Designs Tolerating SOIC Package Migration:

ISL12008IB8Z-T and M41T82RM6F provide functional equivalence with 8-SOIC packaging. Both maintain I2C interface compatibility, support 24-hour time format, and operate across -40°C to 85°C. ISL12008IB8Z-T offers lower timekeeping current (4µA ~ 6µA), while M41T82RM6F includes alarm and watchdog timer features.

For Enhanced Feature Requirements:

ISL12022MIBZ and M41ST87WSS6F provide expanded functionality with 128B memory, alarm capabilities, and additional supervisory features. These parts accommodate designs requiring SRAM or NVSRAM storage beyond basic timekeeping.

Compliance Considerations:

All recommended active substitutes carry RoHS3 compliance certification, addressing regulatory requirements absent in the obsolete DS1340U-3. The Moisture Sensitivity Level (MSL) of 1 (Unlimited) is maintained across all primary recommendations, ensuring consistent handling requirements.

Frequently Asked Questions (FAQ)

Q: Can DS1340U-3+ be used as a direct replacement without PCB modifications?

A: Yes. DS1340U-3+ maintains identical pin configuration, package dimensions (8-TSSOP/8-MSOP, 0.118" width), and electrical specifications including supply voltage (2.7V ~ 5.5V), battery voltage (1.3V ~ 3.7V), and timekeeping current (125µA @ 3.3V). No circuit changes are required.

Q: What is the primary difference between 8-TSSOP and 8-SOIC packages?

A: Package width differs: 8-TSSOP measures 0.118" (3.00mm) while 8-SOIC measures 0.154" (3.90mm). Pin pitch and footprint are incompatible, requiring PCB redesign for migration between these packages. Electrical functionality remains equivalent.

Q: Why do some substitutes support 12/24-hour time format while DS1340U-3 supports only 24-hour?

A: Enhanced RTC devices offer configurable time format options. Designs using only 24-hour operation can utilize these parts without firmware modification, as the 24-hour mode is standard across all substitutes.

Q: Is battery backup voltage compatibility critical for substitution?

A: Yes. The DS1340U-3 requires battery voltage between 1.3V ~ 3.7V. Substitutes with different battery voltage ranges (such as 1.8V ~ 5.5V) may require battery circuit redesign. Verify battery supply specifications against the selected substitute.

Q: What does RoHS3 compliance mean for the DS1340U-3+ substitute?

A: RoHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements, restricting lead, cadmium, mercury, and other hazardous materials. The original DS1340U-3 is RoHS non-compliant; DS1340U-3+ addresses this regulatory requirement.

Q: Can ISL12022MIBZ or M41ST87WSS6F be used in applications requiring only basic timekeeping?

A: Yes. These parts provide backward-compatible I2C timekeeping functionality. The additional 128B memory and supervisory features do not interfere with basic clock/calendar operation. However, larger package footprints (20-SOIC and 20-SSOP respectively) require PCB redesign.

Q: What is the significance of Moisture Sensitivity Level (MSL) 1 (Unlimited)?

A: MSL 1 indicates unlimited shelf life without moisture exposure precautions. All recommended substitutes maintain this specification, ensuring consistent storage and handling requirements with the original DS1340U-3.

Q: Does AB-RTCMC-32.768KHZ-EOZ9-S3-DBT include an integrated crystal oscillator?

A: Yes. This 10-SMD module integrates the 32.768 kHz crystal oscillator, reducing external component count. The module format requires different PCB layout compared to discrete IC packages but provides a complete timekeeping solution.

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