RX-8581JE:B0 Equivalent & Substitute Parts

Part Overview

The RX-8581JE:B0 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, manufactured by EPSON. It features I2C (2-Wire Serial) interface, alarm capability, and leap year support. The device operates across a wide supply voltage range of 1.8V to 5.5V with minimal timekeeping current consumption of 0.8µA to 1.2µA at 3V to 5V. Housed in a 20-LSSOJ surface mount package, this component is currently classified as obsolete. Due to its discontinued status, equivalent substitute parts with compatible electrical and mechanical characteristics are necessary for ongoing system support and new design implementations.

Key Parameters

Parameter	RX-8581JE:B0
Manufacturer	EPSON
Category	Clock/Timing
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Features	Alarm, Leap Year
Time Format	HH:MM:SS (24 hr)
Date Format	YY-MM-DD-dd
Voltage - Supply	1.8V ~ 5.5V
Current - Timekeeping (Max)	0.8µA ~ 1.2µA @ 3V ~ 5V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	20-LSSOJ (0.213", 5.40mm Width)
Product Status	Obsolete
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the RX-8581JE:B0 is determined by strict alignment of the following electrical and mechanical parameters:

Critical Substitution Criteria:

Interface: I2C, 2-Wire Serial (mandatory match)
Time Format: 24-hour capability (mandatory match)
Date Format: YY-MM-DD-dd support (mandatory match)
Features: Alarm and Leap Year support (mandatory match)
Voltage Supply Range: Minimum 1.8V to 5.5V compatibility
Operating Temperature: -40°C to 85°C range
Mounting Type: Surface Mount
RoHS Compliance: ROHS3 Compliant

Substitute parts are grouped into two categories based on package compatibility and electrical performance:

Group 1 - Compact Package Alternatives (8-pin packages): Parts with reduced pin counts and smaller form factors that maintain full functional compatibility through optimized pin assignments. These include 8-TSSOP, 8-MSOP, 8-SOIC, and 8-WCDFN packages.

Group 2 - Extended Package Alternatives (16-pin packages): Parts with additional pins that provide expanded functionality while maintaining core RTC/Calendar operations.

Parameter Comparison

Parameter	RX-8581JE:B0	1337DVGI	1338-31DVGI8	AB-RTCMC-32.768KHZ-AIGZ-S7-T	BU9873FVT-GE2	DS1308U-33+T	DS1338Z-18+	DS1338Z-3+	DS1339U-3+T&R	DS1340C-33#	DS1340Z-33+
Manufacturer	EPSON	Renesas Electronics	Renesas Electronics	Abracon LLC	Rohm Semiconductor	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim
Interface	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial
Type	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar	Clock/Calendar
Time Format	HH:MM:SS (24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS:hh (24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	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)
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	YY-MM-DD-dd	YY-MM-DD-dd
Features	Alarm, Leap Year	Alarm, Leap Year, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Alarm, Leap Year, Watchdog Timer	Alarm, Leap Year	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Leap Year, NVSRAM, Square Wave Output	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Leap Year, Trickle-Charger	Leap Year, Trickle-Charger
Voltage - Supply	1.8V ~ 5.5V	1.8V ~ 5.5V	3.3V ~ 5.5V	1V ~ 4.4V	1.8V ~ 5.5V	3V ~ 5.5V	1.71V ~ 5.5V	2.7V ~ 5.5V	2.7V ~ 5.5V	2.97V ~ 5.5V	2.97V ~ 5.5V
Current - Timekeeping (Max)	0.8µA ~ 1.2µA @ 3V ~ 5V	0.6µA @ 1.3V ~ 1.8V	5µA @ 3.63V ~ 5.5V	0.4µA ~ 0.95µA @ 1V ~ 4.4V	1µA ~ 1.35µA @ 3V ~ 5.5V	125µA ~ 200µA @ 3V ~ 5.5V	100µA @ 1.89V	200µA @ 3.3V	150µA @ 3.3V	150µA @ 5.5V	150µA @ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	20-LSSOJ (0.213", 5.40mm Width)	8-TSSOP, 8-MSOP (0.118", 3.00mm Width)	8-TSSOP, 8-MSOP (0.118", 3.00mm Width)	8-WCDFN	8-TSSOP (0.173", 4.40mm Width)	8-TSSOP, 8-MSOP (0.118", 3.00mm Width)	8-SOIC (0.154", 3.90mm Width)	8-SOIC (0.154", 3.90mm Width)	8-TSSOP, 8-MSOP (0.118", 3.00mm Width)	16-SOIC (0.295", 7.50mm Width)	8-SOIC (0.154", 3.90mm Width)
Product Status	Obsolete	Active	Active	Active	Not For New Designs	Active	Active	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	3 (168 Hours)	3 (168 Hours)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Primary Substitutes (Active Product Status):

The following parts are recommended as primary substitutes due to active product status and full compliance with RoHS3 standards:

1337DVGI (Renesas Electronics Corporation) - Compact 8-TSSOP package with full I2C interface, 24-hour time format capability, alarm and leap year features. Voltage range 1.8V to 5.5V matches the original specification. MSL rating of 3 requires controlled storage conditions. Active product status ensures long-term availability.

1338-31DVGI8 (Renesas Electronics Corporation) - 8-MSOP package with integrated 56B NVSRAM, square wave output, and leap year support. Voltage range limited to 3.3V to 5.5V. Active product status with higher inventory availability (1335 pcs).

AB-RTCMC-32.768KHZ-AIGZ-S7-T (Abracon LLC) - 8-WCDFN package with watchdog timer feature and extended voltage range of 1V to 4.4V. MSL rating of 1 (Unlimited) matches the original part. Highest inventory availability (84205 pcs). Active product status.

DS1338Z-18+ (Analog Devices Inc./Maxim Integrated) - 8-SOIC package with 56B NVSRAM and square wave output. Voltage range 1.71V to 5.5V provides broad compatibility. Active product status with substantial inventory (50200 pcs).

DS1338Z-3+ (Analog Devices Inc./Maxim Integrated) - 8-SOIC package variant with voltage range 2.7V to 5.5V. Active product status with 3900 pcs inventory.

DS1339U-3+T&R (Analog Devices Inc./Maxim Integrated) - 8-TSSOP package with trickle-charger and square wave output. Voltage range 2.7V to 5.5V. Active product status with 4100 pcs inventory.

DS1340C-33# (Analog Devices Inc./Maxim Integrated) - 16-SOIC package with trickle-charger and 24-hour time format. Voltage range 2.97V to 5.5V. Active product status with 22916 pcs inventory.

DS1340Z-33+ (Analog Devices Inc./Maxim Integrated) - 8-SOIC package with trickle-charger and 24-hour time format. Voltage range 2.97V to 5.5V. Active product status with 2838 pcs inventory.

Secondary Substitute (Not For New Designs):

BU9873FVT-GE2 (Rohm Semiconductor) - 8-TSSOP package with alarm and leap year features. Voltage range 1.8V to 5.5V matches original specification. Product status is "Not For New Designs," limiting suitability for new implementations but acceptable for legacy system support.

Frequently Asked Questions (FAQ)

Q: Can the RX-8581JE:B0 be directly replaced with a smaller package substitute?

A: Direct pin-for-pin replacement is not possible due to package differences (20-LSSOJ vs. 8-pin packages). However, functional substitution is achievable through I2C interface compatibility. PCB layout redesign is required to accommodate the different package footprint. All listed substitutes maintain I2C, 2-Wire Serial interface and support the required time/date formats.

Q: What is the impact of different MSL ratings on substitute selection?

A: The original RX-8581JE:B0 has MSL 1 (Unlimited), indicating no moisture sensitivity restrictions. Substitutes with MSL 3 (1337DVGI, 1338-31DVGI8) require controlled storage at 23°C ± 2°C and 45% ± 5% relative humidity for 168 hours maximum before reflow soldering. For applications with extended storage or high-humidity environments, select substitutes with MSL 1 rating: AB-RTCMC-32.768KHZ-AIGZ-S7-T, BU9873FVT-GE2, or Analog Devices DS series parts.

Q: Which substitute offers the lowest timekeeping current consumption?

A: AB-RTCMC-32.768KHZ-AIGZ-S7-T provides the lowest timekeeping current at 0.4µA to 0.95µA across its 1V to 4.4V supply range. This is followed by 1337DVGI at 0.6µA at 1.3V to 1.8V. For battery-backed applications requiring extended runtime, these options are preferred.

Q: Are all substitutes RoHS3 compliant?

A: Yes, all listed substitute parts are ROHS3 Compliant, matching the original RX-8581JE:B0 compliance status. All parts carry ECCN EAR99 and HTSUS 8542.39.0001 classifications.

Q: What is the difference between 24-hour and 12/24-hour time format support?

A: The RX-8581JE:B0 supports 24-hour format exclusively. Most substitutes (1337DVGI, 1338-31DVGI8, BU9873FVT-GE2, DS1308U-33+T, DS1338Z-18+, DS1338Z-3+, DS1339U-3+T&R) support both 12-hour and 24-hour formats, providing operational flexibility. DS1340C-33# and DS1340Z-33+ support 24-hour format exclusively, matching the original specification exactly.

Q: Which substitutes are recommended for new designs?

A: For new designs, select from parts with Active product status: 1337DVGI, 1338-31DVGI8, AB-RTCMC-32.768KHZ-AIGZ-S7-T, DS1308U-33+T, DS1338Z-18+, DS1338Z-3+, DS1339U-3+T&R, DS1340C-33#, or DS1340Z-33+. Avoid BU9873FVT-GE2 (Not For New Designs status) for new implementations.

Q: How do voltage supply ranges affect substitute selection?

A: The original RX-8581JE:B0 operates from 1.8V to 5.5V. Substitutes with matching or broader ranges ensure compatibility with existing power supply designs. AB-RTCMC-32.768KHZ-AIGZ-S7-T extends to 1V minimum, while DS1338Z-18+ reaches 1.71V minimum. Parts with higher minimum voltages (DS1340C-33# and DS1340Z-33+ at 2.97V) require verification against system power supply specifications.

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