DS1391U-33 Equivalent & Substitute Parts

Part Overview

The DS1391U-33 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, manufactured by Analog Devices Inc./Maxim Integrated. This device integrates SPI interface communication, alarm capability, leap year compensation, square wave output, and trickle-charger functionality in a compact 10-TFSOP/10-MSOP surface mount package. The DS1391U-33 is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility across core timing, interface, and electrical parameters while accommodating packaging and performance variations.

Substiute Parts

DS1391U-33

Analog Devices Inc./Maxim IntegratedIn Stock: 4315DS1391U-33 Datasheet

Current PartRFQ

DS1391U-3+

Analog Devices Inc./Maxim IntegratedIn Stock: 1089DS1391U-3+ Datasheet

MFR RecommendedRFQ

CDP68HC68T1M2Z

Renesas Electronics CorporationIn Stock: 3259CDP68HC68T1M2Z Datasheet

MFR RecommendedRFQ

MCP795W10-I/SL

Microchip TechnologyIn Stock: 2091MCP795W10-I/SL Datasheet

MFR RecommendedRFQ

MCP795W10T-I/SL

Microchip TechnologyIn Stock: 1070MCP795W10T-I/SL Datasheet

MFR RecommendedRFQ

MCP795W21T-I/ST

Microchip TechnologyIn Stock: 877MCP795W21T-I/ST Datasheet

MFR RecommendedRFQ

PCF2123BS/1,518

NXP USA Inc.In Stock: 3277PCF2123BS/1,518 Datasheet

MFR RecommendedRFQ

PCF2123TS/1,112

NXP USA Inc.In Stock: 993PCF2123TS/1,112 Datasheet

MFR RecommendedRFQ

PCF85063BTL/1,118

NXP USA Inc.In Stock: 21320PCF85063BTL/1,118 Datasheet

MFR RecommendedRFQ

RX-4803LC:UA PURE SN

EPSONIn Stock: 1165RX-4803LC:UA PURE SN Datasheet

MFR RecommendedRFQ

RX-4803SA:UB PURE SN

EPSONIn Stock: 910RX-4803SA:UB PURE SN Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the DS1391U-33 is determined by the following critical parameters:

Interface Compatibility: All substitute parts must support SPI interface to maintain firmware and PCB design compatibility.

Time and Date Format: Substitute parts must support at minimum HH:MM:SS time format and YY-MM-DD date format with day-of-week capability.

Operating Temperature Range: All substitutes must cover the full -40°C to 85°C operating range.

Voltage Supply Compatibility: Substitute parts must operate within overlapping supply voltage ranges. The DS1391U-33 operates from 2.97V to 5.5V; substitutes with narrower ranges (such as 1.8V to 3.6V) are acceptable if the target application voltage falls within both ranges.

Core Features: Alarm and Leap Year compensation are mandatory. Square Wave Output is required. Additional features (EEPROM, SRAM, Watchdog Timer, Unique ID) represent functional enhancements and do not disqualify a substitute.

Packaging and Mounting: Surface mount technology is required. Package form factor variations (10-TFSOP, 14-SOIC, 14-TSSOP, 16-VFQFN, 10-DFN, 12-TFSOJ) are acceptable provided PCB layout can accommodate the physical dimensions.

Compliance: All substitutes must maintain ROHS3 compliance and acceptable MSL ratings for manufacturing processes.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitute - Same Manufacturer (Active Status): DS1391U-3+ is the direct active equivalent from Analog Devices Inc./Maxim Integrated. This part maintains identical functionality, package form factor, and feature set. The primary difference is narrower supply voltage range (2.7V to 3.3V versus 2.97V to 5.5V) and reduced timekeeping current (125µA versus 175µA). Selection of DS1391U-3+ is appropriate for applications operating within the 2.7V to 3.3V supply window. This part carries ROHS3 compliance and MSL-1 rating, matching the original specification.

Microchip MCP795W Series (Active Status, Enhanced Features): MCP795W10-I/SL, MCP795W10T-I/SL, and MCP795W21T-I/ST represent functionally enhanced alternatives with active product status. These parts integrate additional memory (64B EEPROM and SRAM), watchdog timer, and in the case of MCP795W21T-I/ST, unique ID functionality. Supply voltage range is 1.8V to 3.6V with exceptional timekeeping current of 1µA. Package variations (14-SOIC and 14-TSSOP) require PCB layout modification. All three carry ROHS3 compliance and MSL-1 rating. These parts are suitable for applications requiring extended battery life and additional on-chip memory.

NXP PCF Series (Active Status, Low Power): PCF2123BS/1,518, PCF2123TS/1,112, and PCF85063BTL/1,118 offer ultra-low timekeeping current (0.33µA to 0.6µA) with wide supply voltage compatibility (1.6V to 5.5V for PCF2123 series; 0.9V to 5.5V for PCF85063). PCF2123 variants support 12/24-hour time format and include watchdog timer. PCF85063BTL/1,118 operates across the widest voltage range. Package variations (16-VFQFN, 14-TSSOP, 10-XFDFN) require PCB redesign. PCF2123 series carries MSL-3 rating (168 hours); PCF85063 carries MSL-1. These parts are optimal for battery-powered applications with extended operational life requirements.

Renesas CDP68HC68T1M2Z (Active Status, Extended Memory): This 16-SOIC package device integrates 32B memory and watchdog timer with supply range 3V to 6V. Timekeeping current ranges from 20µA to 500µA at 5V. MSL-3 rating (168 hours) requires controlled storage conditions. This part is suitable for applications with higher supply voltage tolerance and memory requirements, though package size increase necessitates PCB layout modification.

EPSON RX-4803 Series (Active Status, Compact Packages): RX-4803LC:UA (12-TFSOJ) and RX-4803SA:UB (14-SOIC) provide compact alternatives with 24-hour time format only (no 12-hour mode). Supply voltage range is 1.6V to 5.5V with timekeeping current of 2.1µA to 3.4µA. Both parts lack square wave output capability. REACH compliance status is affected. These parts are suitable for applications where 24-hour format is acceptable and square wave output is not required.

Compliance and Certification: All recommended substitutes maintain ROHS3 compliance. MSL ratings vary: MSL-1 (unlimited shelf life) is preferred for standard manufacturing; MSL-3 (168-hour limit) requires controlled storage. All parts operate across the full -40°C to 85°C temperature range. Selection should prioritize active product status and compliance certifications matching the original design requirements.

Frequently Asked Questions (FAQ)

Q: Can DS1391U-3+ be used as a direct replacement for DS1391U-33 in all applications?

A: DS1391U-3+ is functionally equivalent and uses the same package. However, the supply voltage range is narrower (2.7V to 3.3V versus 2.97V to 5.5V). Verify that your application operates within the 2.7V to 3.3V window. If your design requires operation above 3.3V or below 2.7V, alternative substitutes must be evaluated.

Q: What is the primary advantage of Microchip MCP795W series over the DS1391U-33?

A: The MCP795W series provides integrated 64B EEPROM and SRAM memory, watchdog timer functionality, and significantly lower timekeeping current (1µA versus 175µA). These enhancements extend battery life in portable applications. The trade-off is package size increase (14-pin SOIC or TSSOP versus 10-pin TFSOP) and narrower supply voltage range (1.8V to 3.6V).

Q: Are NXP PCF2123 and PCF85063 suitable for high-voltage applications?

A: PCF2123 series supports 1.6V to 5.5V supply range, and PCF85063 supports 0.9V to 5.5V. Both are suitable for 5V applications. However, verify that your PCB layout can accommodate the different package forms (16-VFQFN for PCF2123BS, 14-TSSOP for PCF2123TS, 10-XFDFN for PCF85063). The primary advantage of NXP parts is ultra-low timekeeping current, beneficial for battery-backed designs.

Q: What is the impact of MSL rating on component selection?

A: MSL-1 rated parts (DS1391U-3+, MCP795W series, PCF85063, EPSON RX-4803) have unlimited shelf life and are preferred for standard manufacturing environments. MSL-3 rated parts (CDP68HC68T1M2Z, PCF2123BS) require storage below 30°C and 60% relative humidity, with a 168-hour limit after moisture exposure. If your manufacturing process includes extended storage or high-humidity environments, MSL-1 parts are recommended.

Q: Can EPSON RX-4803 series be used if square wave output is not required?

A: Yes, if your application does not require square wave output functionality. However, RX-4803 series supports only 24-hour time format (no 12-hour mode). Verify that your firmware and application logic are compatible with 24-hour format operation. REACH compliance status is affected for EPSON parts; confirm regulatory requirements for your target market.

Q: What package considerations apply when selecting a substitute?

A: The DS1391U-33 uses 10-TFSOP/10-MSOP package. Substitute parts use various packages: 14-SOIC, 14-TSSOP, 16-VFQFN, 10-XFDFN, and 12-TFSOJ. Each package has different pin counts, pitch, and physical dimensions. PCB layout modification is required for any package change. Verify that your PCB design can accommodate the selected substitute's package form factor, including trace routing, via placement, and component spacing.

Q: Which substitute offers the best battery life for portable applications?

A: NXP PCF2123 series (0.33µA to 0.38µA timekeeping current) and PCF85063 (0.6µA at 3.3V) provide the lowest timekeeping current, extending battery life significantly compared to DS1391U-33 (175µA). Microchip MCP795W series (1µA) offers a middle ground with additional on-chip memory. Selection depends on your specific power budget and memory requirements.

Q: Are all substitutes ROHS3 compliant?

A: Yes, all recommended substitutes maintain ROHS3 compliance. This ensures compatibility with environmental regulations and procurement requirements matching the original DS1391U-33 specification.