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RX-8581SA:B Real Time Clock (RTC) IC Equivalent & Substitute Parts
Part Overview
The RX-8581SA:B is an EPSON Real Time Clock (RTC) IC designed for clock/calendar applications with I2C 2-Wire Serial interface. This 14-SOIC surface mount device operates across 1.8V to 5.5V supply voltage with ultra-low timekeeping current consumption of 0.8µA to 1.2µA at 3V to 5V. The device is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility through matching interface protocols, time/date format support, operating temperature range, and supply voltage specifications.
Substiute Parts
Key Parameters
| Parameter | RX-8581SA:B |
|---|---|
| Manufacturer | EPSON |
| Category | Clock/Timing |
| Type | Clock/Calendar |
| Interface | I2C, 2-Wire Serial |
| 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 | 14-SOIC (0.209", 5.30mm Width) |
| Features | Alarm, Leap Year |
| RoHS Status | ROHS3 Compliant |
| Product Status | Obsolete |
Substitute Part Grouping Explanation
Substitution logic for the RX-8581SA:B is based on the following critical parameters:
- Interface Protocol: I2C 2-Wire Serial (mandatory match)
- Time Format: 24-hour HH:MM:SS support (mandatory match)
- Date Format: YY-MM-DD-dd support (mandatory match)
- Supply Voltage Range: Minimum 1.8V to 5.5V overlap required
- Operating Temperature: -40°C to 85°C range (mandatory match)
- Mounting Type: Surface Mount (mandatory match)
- Features: Alarm and Leap Year support (core functionality)
Substitute parts are grouped into two categories based on package compatibility:
Group 1 - Compact Package Alternatives (8-pin packages): Parts with reduced pin count but equivalent functional capability. These require PCB layout redesign due to different package footprints.
Group 2 - Module-Based Alternative: Integrated module solution offering enhanced integration with maintained I2C interface.
Group 3 - Enhanced Feature Variants (8-pin and 8-SOIC packages): Parts with additional features such as NVSRAM, EEPROM, Supervisor, Trickle-Charger, and Watchdog Timer functionality while maintaining core RTC compatibility.
Parameter Comparison
| Parameter | RX-8581SA:B | 1337GDVGI8 | AB-RTCMC-32.768KHZ-B5GA-S3-T | DS1308U-18+T | DS1337U+T&R | DS1338Z-18+T&R | DS1338Z-3+T&R | DS1340U-3+ | DS1341T+T&R | DS1388Z-3+T&R | DS1388Z-33+ |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Manufacturer | EPSON | Renesas Electronics | Abracon LLC | Analog Devices/Maxim | Analog Devices/Maxim | 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 |
| Time Format | HH:MM:SS (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) | HH:MM:SS (24 hr) | HH:MM:SS (12/24 hr) | HH:MM:SS:hh (12/24 hr) | HH:MM:SS:hh (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 |
| Voltage - Supply | 1.8V ~ 5.5V | 1.8V ~ 5.5V | 1.2V ~ 5.5V | 1.71V ~ 5.5V | 1.8V ~ 5.5V | 1.71V ~ 5.5V | 2.7V ~ 5.5V | 2.7V ~ 5.5V | 1.8V ~ 5.5V | 2.7V ~ 3.3V | 2.97V ~ 3.63V |
| Current - Timekeeping (Max) | 0.8µA ~ 1.2µA @ 3V ~ 5V | 0.6µA @ 1.3V ~ 1.8V | 0.45µA ~ 0.55µA @ 2V ~ 5V | 100µA @ 1.89V ~ 5.5V | 0.6µA @ 1.3V ~ 1.8V | 100µA @ 1.89V | 200µA @ 3.3V | 125µA @ 3.3V | 0.5µA ~ 0.6µA @ 3V ~ 5V | 140µA @ 2.7V ~ 3.3V | 150µA @ 2.97V ~ 3.63V |
| 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 | 14-SOIC (0.209", 5.30mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 10-SMD Module | 8-TSSOP, 8-MSOP (0.118", 3.00mm 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) | 8-WDFN Exposed Pad | 8-SOIC (0.154", 3.90mm Width) | 8-SOIC (0.154", 3.90mm Width) |
| Features | Alarm, Leap Year | Alarm, Leap Year, Square Wave Output | Alarm, Leap Year, Square Wave Output | Leap Year, NVSRAM, Square Wave Output | Alarm, Leap Year, Square Wave Output | Leap Year, NVSRAM, Square Wave Output | Leap Year, NVSRAM, Square Wave Output | Leap Year, Trickle-Charger | Alarm, Leap Year, Square Wave Output | EEPROM, Leap Year, Supervisor, Trickle-Charger, Watchdog Timer | EEPROM, Leap Year, Supervisor, Trickle-Charger, Watchdog Timer |
| 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 | Active | Active | Active | Active |
Engineering Selection Recommendations
All listed substitute parts maintain active product status with ROHS3 compliance and REACH compliance status, ensuring long-term availability and regulatory adherence for new designs.
For Direct Pin-Compatible Replacement (14-SOIC Package): No direct 14-SOIC pin-compatible alternatives are available in the provided substitute list. PCB redesign is required for any substitution.
For Compact Footprint Applications (8-pin packages): The 1337GDVGI8 (Renesas), DS1337U+T&R, DS1340U-3+, and DS1341T+T&R offer reduced package sizes with active product status. These require PCB layout modification but provide equivalent I2C interface and 24-hour time format support where applicable.
For Integrated Module Solution: The AB-RTCMC-32.768KHZ-B5GA-S3-T provides a 10-SMD module package with extended supply voltage range (1.2V to 5.5V) and lower timekeeping current (0.45µA to 0.55µA), suitable for ultra-low-power applications.
For Enhanced Feature Requirements: The DS1388Z-3+T&R and DS1388Z-33+ offer 512B EEPROM, Supervisor, Trickle-Charger, and Watchdog Timer functionality. These are suitable for applications requiring additional memory and system monitoring capabilities beyond basic RTC functionality.
For Standard Feature Parity: The DS1338Z-18+T&R and DS1338Z-3+T&R provide 56B NVSRAM with Leap Year and Square Wave Output support, maintaining core RTC functionality with modest additional features.
Frequently Asked Questions (FAQ)
Q: Can I use an 8-pin substitute part as a direct replacement for the 14-SOIC RX-8581SA:B?
A: No. The RX-8581SA:B uses a 14-SOIC package while substitute parts in the 8-pin category (8-TSSOP, 8-MSOP, 8-SOIC, 8-WDFN) have different pin counts and footprints. PCB redesign is required. Verify pin function mapping and I2C address configuration before implementation.
Q: What are the key compatibility criteria for RTC substitution?
A: The critical parameters are I2C 2-Wire Serial interface, 24-hour time format support (or 12/24-hour selectable), YY-MM-DD-dd date format, -40°C to 85°C operating temperature range, and supply voltage overlap with your application requirements. All listed substitutes meet these criteria.
Q: Does the AB-RTCMC-32.768KHZ-B5GA-S3-T module require external crystal oscillator?
A: The module designation indicates integrated 32.768 kHz oscillator functionality. Verify module datasheet for external component requirements and PCB layout considerations specific to module-based integration.
Q: Which substitute offers the lowest timekeeping current consumption?
A: The AB-RTCMC-32.768KHZ-B5GA-S3-T module specifies 0.45µA to 0.55µA at 2V to 5V, providing the lowest timekeeping current among listed alternatives. The DS1341T+T&R specifies 0.5µA to 0.6µA at 3V to 5V as a discrete IC alternative.
Q: Are all substitute parts RoHS3 compliant?
A: Yes. All listed substitute parts carry ROHS3 Compliant status, meeting environmental and regulatory requirements for new product designs.
Q: What is the difference between DS1338Z-18+T&R and DS1338Z-3+T&R?
A: Both use 8-SOIC package with 56B NVSRAM. The DS1338Z-18+T&R operates at 1.71V to 5.5V supply voltage, while DS1338Z-3+T&R operates at 2.7V to 5.5V. Select based on your minimum supply voltage requirement. Timekeeping current differs: 100µA at 1.89V versus 200µA at 3.3V respectively.
Q: Can I use DS1388Z series parts as drop-in replacements?
A: DS1388Z-3+T&R and DS1388Z-33+ are not drop-in replacements due to different package (8-SOIC) and restricted supply voltage range (2.7V to 3.3V or 2.97V to 3.63V). However, they provide enhanced features including 512B EEPROM, Supervisor, Trickle-Charger, and Watchdog Timer. Use only if your application supports the narrower voltage range and requires these additional functions.
Q: What packaging options are available for high-volume production?
A: Substitute parts are available in multiple packaging formats: Tape & Reel (TR), Cut Tape (CT) & Digi-Reel, Tube, and Module. Select based on your assembly process requirements and volume specifications.
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