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RX-8581JE:B3 I2C-BUS Equivalent & Substitute Parts
Part Overview
The RX-8581JE:B3 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, featuring I2C 2-Wire Serial interface in a 20-LSSOJ surface mount package. This component is classified as Obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The RX-8581JE:B3 provides timekeeping with alarm and leap year capabilities across a wide supply voltage range of 1.8V to 5.5V, with ultra-low timekeeping current consumption suitable for battery-backed applications.
Substiute Parts
Key Parameters
| Parameter | RX-8581JE:B3 |
|---|---|
| Manufacturer | EPSON |
| Category | Clock/Timing |
| Type | Clock/Calendar |
| Interface | I2C, 2-Wire Serial |
| Package / Case | 20-LSSOJ (0.213", 5.40mm Width) |
| Voltage - Supply | 1.8V ~ 5.5V |
| Current - Timekeeping (Max) | 0.8µA ~ 1.2µA @ 3V ~ 5V |
| Operating Temperature | -40°C ~ 85°C |
| Time Format | HH:MM:SS (24 hr) |
| Date Format | YY-MM-DD-dd |
| Features | Alarm, Leap Year |
| Mounting Type | Surface Mount |
| RoHS Status | ROHS3 Compliant |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
| Product Status | Obsolete |
Substitute Part Grouping Explanation
Substitution of the RX-8581JE:B3 is determined by the following critical parameters:
Interface Compatibility: All substitute parts must support I2C 2-Wire Serial communication to maintain firmware and circuit compatibility.
Voltage Supply Range: The RX-8581JE:B3 operates from 1.8V to 5.5V. Substitute parts must support this full range or a compatible subset that covers the application's operating voltage.
Timekeeping Current: Ultra-low timekeeping current (0.8µA ~ 1.2µA @ 3V ~ 5V) is critical for battery-backed operation. Substitute parts with significantly higher timekeeping current may require circuit redesign.
Operating Temperature: All substitutes must maintain -40°C to 85°C operating range for industrial and automotive applications.
Time/Date Format: The 24-hour HH:MM:SS format and YY-MM-DD-dd date format must be supported or software-compatible.
Core Features: Alarm and Leap Year functionality are essential for calendar-based timekeeping applications.
Package Consideration: The 20-LSSOJ package is specific to the RX-8581JE:B3. Substitute parts in different packages (8-TSSOP, 8-SOIC, 10-SMD Module) require PCB redesign and are suitable only when layout flexibility exists.
Parameter Comparison
| Parameter | RX-8581JE:B3 | 1337AGDVGI8 | 1337GDCGI8 | 1339-31DVGI | AB-RTCMC-32.768KHZ-B5ZE-S3-T | AB-RTCMC-32.768KHZ-EOZ9-S3-DBT | BQ32002D | BU9873NUX-TTR | DS1308U-3+T | DS1338Z-33+T&R | DS1339U-33+T&R |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Manufacturer | EPSON | Renesas Electronics | Renesas Electronics | Renesas Electronics | Abracon LLC | Abracon LLC | Texas Instruments | Rohm Semiconductor | 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 |
| Voltage - Supply | 1.8V ~ 5.5V | 1.8V ~ 5.5V | 1.8V ~ 5.5V | 3.3V ~ 5.5V | 1.2V ~ 5.5V | 1.4V ~ 5.5V | 3V ~ 3.6V | 1.8V ~ 5.5V | 2.7V ~ 5.5V | 3V ~ 5.5V | 2.97V ~ 5.5V |
| Current - Timekeeping (Max) | 0.8µA ~ 1.2µA @ 3V ~ 5V | 0.3µA @ 1.3V ~ 1.8V | 0.6µA @ 1.3V ~ 1.8V | 200µA @ 3.63V ~ 5.5V | 0.5µA @ 2V ~ 5V | 1.5µA ~ 2.2µA @ 1.4V ~ 5V | 200µA @ 3.3V | 1µA ~ 1.35µA @ 3V ~ 5.5V | Not Specified | 125µA ~ 200µA @ 3.63V ~ 5.5V | 200µA @ 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 |
| Time Format | HH:MM:SS (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 (12/24 hr) | HH:MM:SS (12/24 hr) | HH:MM:SS (12/24 hr) | HH:MM:SS (12/24 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 | Alarm, Leap Year, Square Wave Output | Alarm, Leap Year, Square Wave Output, Trickle-Charger | Alarm, Leap Year, Square Wave Output | Alarm, EEPROM, Leap Year, Square Wave Output, SRAM, TCXO/Crystal, Trickle-Charger | Leap Year, Square Wave Output, Trickle-Charger | Alarm, Leap Year | Leap Year, NVSRAM, Square Wave Output | Leap Year, NVSRAM, Square Wave Output | Alarm, Leap Year, Square Wave Output, Trickle-Charger |
| Package / Case | 20-LSSOJ (0.213", 5.40mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 8-SOIC (0.154", 3.90mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 10-SMD Module | 10-SMD Module | 8-SOIC (0.154", 3.90mm Width) | 8-UFDFN Exposed Pad | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 8-SOIC (0.154", 3.90mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) |
| Mounting Type | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount |
| RoHS Status | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant |
| Product Status | Obsolete | Active | Active | Active | Active | Active | Active | Not For New Designs | Active | Active | Active |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) | 3 (168 Hours) | 1 (Unlimited) | 3 (168 Hours) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) |
Engineering Selection Recommendations
Primary Substitutes (Active Status, Full Voltage Range Compatibility):
The 1337GDCGI8 (Renesas Electronics) and DS1338Z-33+T&R (Analog Devices/Maxim) are the most direct functional substitutes. Both support the full 1.8V to 5.5V supply range, maintain I2C 2-Wire Serial interface compatibility, and are in Active product status. The 1337GDCGI8 offers superior timekeeping current efficiency (0.6µA) and unlimited MSL rating. The DS1338Z-33+T&R provides 56B NVSRAM memory and is widely available with 12,974 units in stock.
Secondary Substitutes (Partial Voltage Range, Active Status):
The DS1339U-33+T&R (Analog Devices/Maxim) operates from 2.97V to 5.5V and includes trickle-charger functionality. This part is suitable for applications where the lower voltage limit of 1.8V is not required. The 1337AGDVGI8 (Renesas Electronics) provides the lowest timekeeping current (0.3µA) but operates from 1.8V to 5.5V with MSL-3 rating requiring controlled storage conditions.
Module-Based Alternatives (Integrated Solutions):
The AB-RTCMC-32.768KHZ-EOZ9-S3-DBT (Abracon LLC) is a 10-SMD module integrating RTC, crystal, and support components. This part includes EEPROM, SRAM, and trickle-charger, reducing external component count. It operates from 1.4V to 5.5V with 1.5µA to 2.2µA timekeeping current and unlimited MSL rating. Module-based substitution requires PCB redesign but simplifies integration.
Voltage-Constrained Applications:
The BQ32002D (Texas Instruments) operates within 3V to 3.6V range and is suitable only for applications with fixed 3.3V supply. This part includes trickle-charger and square wave output but is not recommended for multi-voltage systems.
Discontinued Status Consideration:
The BU9873NUX-TTR (Rohm Semiconductor) is marked "Not For New Designs" and should be avoided for new product development despite active inventory availability.
Frequently Asked Questions (FAQ)
Q: Can the RX-8581JE:B3 be directly replaced with a smaller package substitute without PCB modification?
A: No. The RX-8581JE:B3 uses a 20-LSSOJ package, while most substitutes (1337AGDVGI8, 1337GDCGI8, DS1339U-33+T&R) use 8-pin packages (8-TSSOP or 8-SOIC). Direct replacement requires PCB redesign. Module-based alternatives (AB-RTCMC series) also require layout changes.
Q: Which substitute offers the lowest power consumption for battery-backed timekeeping?
A: The 1337AGDVGI8 provides the lowest timekeeping current at 0.3µA when operating from 1.3V to 1.8V. However, for operation across the full 1.8V to 5.5V range, the 1337GDCGI8 offers 0.6µA timekeeping current, which is superior to the original RX-8581JE:B3 specification of 0.8µA to 1.2µA.
Q: Are all substitutes RoHS3 compliant?
A: Yes. All listed substitute parts maintain ROHS3 compliance, matching the original RX-8581JE:B3 environmental certification.
Q: What is the impact of MSL-3 rating on substitute parts?
A: Parts with MSL-3 rating (1337AGDVGI8, 1339-31DVGI) require controlled storage conditions of 168 hours maximum at specified humidity levels before soldering. Parts with MSL-1 rating (unlimited) have no storage restrictions. This affects supply chain handling and production scheduling.
Q: Can the 24-hour time format requirement be met by 12/24-hour capable substitutes?
A: Yes. All substitutes supporting 12/24-hour format can be configured for 24-hour operation through firmware or register settings. This does not impact hardware compatibility.
Q: Which substitute is recommended for new product designs?
A: The DS1338Z-33+T&R (Analog Devices/Maxim) or 1337GDCGI8 (Renesas Electronics) are recommended for new designs. Both are in Active product status, offer wide voltage range support, and have substantial inventory availability. The DS1338Z-33+T&R includes 56B NVSRAM for additional data storage, while the 1337GDCGI8 provides superior timekeeping current efficiency.
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