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PCF2129AT/2,518 Real Time Clock IC - Equivalent & Substitute Parts
Part Overview
The PCF2129AT/2,518 is an NXP Semiconductors Real Time Clock (RTC) IC with integrated clock/calendar functionality, I2C 2-Wire Serial interface, and comprehensive timekeeping features including alarm, leap year compensation, square wave output, and watchdog timer capability. This 20-SOIC surface mount device operates across 1.8V to 4.2V supply range with ultra-low timekeeping current of 1.5µA at 3.3V, making it suitable for battery-backed and low-power applications. The part maintains Active product status with ROHS3 compliance and unlimited availability in inventory. Substitute parts are identified based on functional equivalence in clock/calendar operation, I2C interface compatibility, operating temperature range, and surface mount packaging options that accommodate design flexibility while maintaining core RTC functionality.
Substiute Parts
Key Parameters
| Parameter | PCF2129AT/2,518 |
|---|---|
| Manufacturer | NXP Semiconductors |
| Category | Clock/Timing |
| Type | Clock/Calendar |
| Interface | I2C, 2-Wire Serial |
| Package / Case | 20-SOIC (0.295", 7.50mm Width) |
| Voltage - Supply | 1.8V ~ 4.2V |
| Voltage - Supply, Battery | 1.8V ~ 4.2V |
| Current - Timekeeping (Max) | 1.5µA @ 3.3V |
| Operating Temperature | -40°C ~ 85°C |
| Time Format | HH:MM:SS (12/24 hr) |
| Date Format | YY-MM-DD-dd |
| Features | Alarm, Leap Year, Square Wave Output, TCXO/Crystal, Watchdog Timer |
| Mounting Type | Surface Mount |
| Product Status | Active |
| RoHS Status | ROHS3 Compliant |
Substitute Part Grouping Explanation
Substitute parts are classified based on strict adherence to the following substitution criteria derived from the PCF2129AT/2,518 specifications:
Primary Substitution Criteria:
- Interface: I2C, 2-Wire Serial (mandatory)
- Type: Clock/Calendar with timekeeping capability
- Operating Temperature: -40°C ~ 85°C (mandatory)
- Mounting Type: Surface Mount
- Product Status: Active
- RoHS Compliance: ROHS3 Compliant
- Voltage Supply Range: Overlap with 1.8V ~ 4.2V or extended range compatibility
Secondary Compatibility Factors:
- Time Format: HH:MM:SS with 12/24 hour capability
- Date Format: YY-MM-DD-dd
- Features: Alarm and Leap Year support (core features)
- Package options: Alternative SOIC or compact surface mount packages acceptable for board redesign scenarios
Substitutes are grouped by packaging category (SOIC variants, compact modules, and alternative form factors) while maintaining functional equivalence in clock/calendar operation and I2C protocol compatibility. All listed substitutes meet Active product status and ROHS3 compliance requirements.
Parameter Comparison
| Parameter | PCF2129AT/2,518 | AB-RTCMC-32.768KHZ-B5GA-S3-T | DS1308U-18+ | DS1337C# | DS1338Z-33+T&R | DS1339U-2+ | DS1339U-33+T&R | DS1340C-3# | DS1342U+T&R | DS1388Z-33+T&R | DS3231S#T&R |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Manufacturer | NXP Semiconductors | Abracon LLC | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated | Analog Devices Inc./Maxim Integrated |
| Type | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar | Clock/Calendar |
| 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 |
| Package / Case | 20-SOIC (0.295", 7.50mm Width) | 10-SMD Module | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 16-SOIC (0.295", 7.50mm Width) | 8-SOIC (0.154", 3.90mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 16-SOIC (0.295", 7.50mm Width) | 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) | 8-SOIC (0.154", 3.90mm Width) | 16-SOIC (0.295", 7.50mm Width) |
| Voltage - Supply | 1.8V ~ 4.2V | 1.2V ~ 5.5V | 1.71V ~ 5.5V | 1.8V ~ 5.5V | 3V ~ 5.5V | 1.8V ~ 5.5V | 2.97V ~ 5.5V | 2.7V ~ 5.5V | 1.8V ~ 5.5V | 2.97V ~ 3.63V | 2.3V ~ 5.5V |
| Voltage - Supply, Battery | 1.8V ~ 4.2V | - | 1.3V ~ 5.5V | - | 1.3V ~ 3.7V | 1.3V ~ 3.7V | 1.3V ~ 3.7V | 1.3V ~ 3.7V | - | 1.3V ~ 5.5V | 2.3V ~ 5.5V |
| Current - Timekeeping (Max) | 1.5µA @ 3.3V | 0.45µA ~ 0.55µA @ 2V ~ 5V | 100µA @ 200µA @ 1.89V ~ 5.5V | 0.6µA @ 1.3V ~ 1.8V | 125µA ~ 200µA @ 3.63V ~ 5.5V | 100µA @ 2.2V | 200µA @ 5.5V | 125µA @ 3.3V | 0.6µA ~ 0.7µA @ 3V ~ 5V | 150µA @ 2.97V ~ 3.63V | 110µA ~ 170µA @ 3.63V ~ 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 | 0°C ~ 70°C |
| Time Format | 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 (12/24 hr) | HH:MM:SS (24 hr) | HH:MM:SS (12/24 hr) | HH:MM:SS:hh (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, Square Wave Output, TCXO/Crystal, Watchdog Timer | Alarm, Leap Year, Square Wave Output | Leap Year, NVSRAM, Square Wave Output | Alarm, Leap Year, Square Wave Output | Leap Year, NVSRAM, Square Wave Output | Alarm, Leap Year, Square Wave Output, Trickle-Charger | Alarm, Leap Year, Square Wave Output, Trickle-Charger | Leap Year, Trickle-Charger | Alarm, Leap Year, Square Wave Output | EEPROM, Leap Year, Supervisor, Trickle-Charger, Watchdog Timer | Alarm, Leap Year, Square Wave Output, TCXO/Crystal |
| Mounting Type | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount |
| Product Status | Active | Active | Active | Active | Active | 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) | 3 (168 Hours) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) |
Engineering Selection Recommendations
All listed substitute parts maintain Active product status and ROHS3 compliance, meeting baseline regulatory and availability requirements for the PCF2129AT/2,518 application space.
Package Compatibility Considerations:
The PCF2129AT/2,518 uses 20-SOIC packaging. Direct pin-compatible substitutes in 20-SOIC or 16-SOIC form factors include DS1337C# and DS1340C-3#, which accommodate minimal PCB redesign. Compact alternatives in 8-SOIC or 8-TSSOP packages (DS1338Z-33+T&R, DS1339U variants, DS1342U+T&R) require board layout modification but offer reduced footprint for space-constrained applications.
Supply Voltage Range Alignment:
The PCF2129AT/2,518 operates 1.8V ~ 4.2V. Substitutes with overlapping or extended ranges include DS1337C# (1.8V ~ 5.5V), DS1339U-2+ (1.8V ~ 5.5V), DS1342U+T&R (1.8V ~ 5.5V), and AB-RTCMC-32.768KHZ-B5GA-S3-T (1.2V ~ 5.5V). DS1340C-3# (2.7V ~ 5.5V) and DS1339U-33+T&R (2.97V ~ 5.5V) require minimum supply voltage verification for 1.8V applications. DS1388Z-33+T&R operates 2.97V ~ 3.63V, limiting compatibility to 3.3V nominal systems.
Operating Temperature Range:
All substitutes except DS3231S#T&R maintain the -40°C ~ 85°C range. DS3231S#T&R operates 0°C ~ 70°C, restricting use to commercial temperature applications.
Feature Alignment:
The PCF2129AT/2,518 includes watchdog timer and TCXO/Crystal support. DS1388Z-33+T&R provides watchdog timer capability with additional EEPROM and supervisor functions. DS3231S#T&R includes TCXO/Crystal support. Substitutes lacking watchdog timer (DS1337C#, DS1338Z-33+T&R, DS1339 variants, DS1340C-3#, DS1342U+T&R, AB-RTCMC-32.768KHZ-B5GA-S3-T) require external watchdog implementation if this function is critical to system design.
Battery Backup Capability:
The PCF2129AT/2,518 supports battery backup 1.8V ~ 4.2V. DS1308U-18+, DS1338Z-33+T&R, DS1339 variants, DS1340C-3#, and DS3231S#T&R provide battery backup ranges. AB-RTCMC-32.768KHZ-B5GA-S3-T and DS1337C# lack specified battery backup voltage, requiring design review for backup power applications.
Current Consumption:
The PCF2129AT/2,518 draws 1.5µA at 3.3V. AB-RTCMC-32.768KHZ-B5GA-S3-T (0.45µA ~ 0.55µA) and DS1342U+T&R (0.6µA ~ 0.7µA) offer superior low-power performance. DS1337C# (0.6µA @ 1.3V ~ 1.8V) provides low current in reduced voltage ranges. Higher current alternatives (DS1308U-18+, DS1338Z-33+T&R, DS1339 variants, DS1340C-3#, DS1388Z-33+T&R, DS3231S#T&R) range 100µA ~ 200µA, suitable for applications where timekeeping current is not a primary constraint.
Frequently Asked Questions (FAQ)
Q: Can DS1337C# directly replace PCF2129AT/2,518 on the same PCB?
A: DS1337C# uses 16-SOIC packaging versus the PCF2129AT/2,518 20-SOIC package. Pin count and pinout differ, requiring PCB redesign. However, both devices provide I2C clock/calendar functionality with -40°C ~ 85°C operation and 1.8V ~ 5.5V supply compatibility, making them functionally equivalent for new board layouts.
Q: Which substitute offers the lowest power consumption?
A: AB-RTCMC-32.768KHZ-B5GA-S3-T draws 0.45µA ~ 0.55µA at 2V ~ 5V, the lowest among listed substitutes. DS1342U+T&R (0.6µA ~ 0.7µA @ 3V ~ 5V) and DS1337C# (0.6µA @ 1.3V ~ 1.8V) provide comparable ultra-low power operation. Selection depends on supply voltage requirements and application duty cycle.
Q: Are all substitutes compatible with 3.3V supply systems?
A: All listed substitutes support 3.3V operation within their specified supply ranges. However, DS1388Z-33+T&R operates 2.97V ~ 3.63V, requiring tight voltage regulation. For 1.8V systems, DS1337C#, DS1339U-2+, DS1342U+T&R, and AB-RTCMC-32.768KHZ-B5GA-S3-T are compatible. DS1340C-3# (2.7V minimum) and DS1339U-33+T&R (2.97V minimum) are not suitable for 1.8V applications.
Q: Does DS3231S#T&R provide equivalent functionality?
A: DS3231S#T&R provides I2C clock/calendar with alarm, leap year, square wave output, and TCXO/Crystal support, matching core PCF2129AT/2,518 features. However, operating temperature is 0°C ~ 70°C versus -40°C ~ 85°C, restricting use to commercial temperature ranges. This substitute is suitable for non-industrial applications.
Q: What is the difference between DS1339U-2+ and DS1339U-33+T&R?
A: Both use identical 8-TSSOP packaging and provide alarm, leap year, square wave output, and trickle-charger features. DS1339U-2+ operates 1.8V ~ 5.5V with 100µA timekeeping current at 2.2V. DS1339U-33+T&R operates 2.97V ~ 5.5V with 200µA timekeeping current at 5.5V. DS1339U-2+ is preferred for low-voltage and low-power applications; DS1339U-33+T&R suits higher voltage systems with less stringent power constraints.
Q: Can I use DS1388Z-33+T&R as a drop-in replacement?
A: DS1388Z-33+T&R uses 8-SOIC packaging, requiring PCB redesign from 20-SOIC. It provides additional features (EEPROM, supervisor, watchdog timer) and operates 2.97V ~ 3.63V, limiting compatibility to 3.3V nominal systems. It is functionally suitable but not a direct pin-compatible replacement.
Q: Which substitute best matches the PCF2129AT/2,518 feature set?
A: DS3231S#T&R most closely matches the PCF2129AT/2,518 by including TCXO/Crystal support alongside alarm, leap year, and square wave output. DS1388Z-33+T&R provides watchdog timer capability equivalent to the PCF2129AT/2,518. Both require packaging and voltage range verification for specific applications.
Q: What packaging options are available for space-constrained designs?
A: Compact 8-SOIC and 8-TSSOP packages are available from DS1338Z-33+T&R, DS1339U variants, DS1342U+T&R, and DS1388Z-33+T&R. AB-RTCMC-32.768KHZ-B5GA-S3-T offers a 10-SMD module form factor for integrated module-based designs. These alternatives reduce PCB footprint compared to the 20-SOIC original.
Q: Are all substitutes ROHS3 compliant?
A: Yes, all listed substitutes maintain ROHS3 compliance. However, moisture sensitivity levels vary. The PCF2129AT/2,518 has MSL 3 (168 hours), while all substitutes have MSL 1 (unlimited), providing superior moisture tolerance and extended shelf life.
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