PCF2129AT/1,512 Real Time Clock IC Equivalent & Substitute Parts

Part Overview

The PCF2129AT/1,512 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, manufactured by NXP USA Inc. This component operates via I2C 2-Wire Serial interface and is housed in a 20-SOIC package. The part is currently listed as obsolete, which necessitates identification of active substitute components that maintain functional and electrical compatibility for new designs or production continuity.

Key Parameters

Parameter	PCF2129AT/1,512
Manufacturer	NXP USA Inc.
Product Status	Obsolete
Package / Case	20-SOIC (0.295", 7.50mm Width)
Interface	I2C, 2-Wire Serial
Type	Clock/Calendar
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
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
Features	Alarm, Leap Year, Square Wave Output, TCXO/Crystal, Watchdog Timer
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	3 (168 Hours)

Substitute Part Grouping Explanation

Substitution of the PCF2129AT/1,512 is determined by the following critical parameters:

Primary Compatibility Criteria:

Interface type: I2C, 2-Wire Serial
Time and Date format support: HH:MM:SS (12/24 hr) and YY-MM-DD-dd
Operating temperature range: -40°C ~ 85°C minimum
Supply voltage overlap: Minimum 1.8V support required
RTC functionality: Clock/Calendar with Alarm capability

Secondary Considerations:

Package form factor (20-SOIC preferred for direct PCB compatibility)
Timekeeping current consumption
Feature set alignment (Leap Year, Square Wave Output)
Product status (Active preferred over Obsolete)

Substitute parts are grouped into two categories: direct package equivalents (20-SOIC) and functional alternatives with different package options (8-SOIC, 8-TSSOP, 16-SOIC).

Parameter Comparison

Part Number	Manufacturer	Package / Case	Interface	Voltage - Supply	Voltage - Battery	Current - Timekeeping (Max)	Operating Temp	Features	Product Status	RoHS Status
PCF2129AT/1,512	NXP USA Inc.	20-SOIC (0.295", 7.50mm)	I2C, 2-Wire Serial	1.8V ~ 4.2V	1.8V ~ 4.2V	1.5µA @ 3.3V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, TCXO/Crystal, Watchdog Timer	Obsolete	ROHS3 Compliant
PCF2129AT/2,518	NXP Semiconductors	20-SOIC (0.295", 7.50mm)	I2C, 2-Wire Serial	1.8V ~ 4.2V	1.8V ~ 4.2V	1.5µA @ 3.3V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, TCXO/Crystal, Watchdog Timer	Active	ROHS3 Compliant
DS1337C#	Analog Devices Inc./Maxim Integrated	16-SOIC (0.295", 7.50mm)	I2C, 2-Wire Serial	1.8V ~ 5.5V	Not specified	0.6µA @ 1.3V ~ 1.8V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output	Active	ROHS3 Compliant
DS1339U-33+T&R	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 3.7V	200µA @ 5.5V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Active	ROHS3 Compliant
DS1340Z-3+	Analog Devices Inc./Maxim Integrated	8-SOIC (0.154", 3.90mm)	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.3V ~ 3.7V	125µA @ 3.3V	-40°C ~ 85°C	Leap Year, Trickle-Charger	Active	ROHS3 Compliant
1338-31DCGI8	Renesas Electronics Corporation	8-SOIC (0.154", 3.90mm)	I2C, 2-Wire Serial	3.3V ~ 5.5V	1.3V ~ 3.7V	5µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Leap Year, NVSRAM, Square Wave Output	Active	ROHS3 Compliant
1339-31DVGI8	Renesas Electronics Corporation	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	3.3V ~ 5.5V	1.3V ~ 3.7V	200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Active	ROHS3 Compliant
DS1307Z+	Analog Devices Inc./Maxim Integrated	8-SOIC (0.154", 3.90mm)	I2C, 2-Wire Serial	4.5V ~ 5.5V	2V ~ 4.6V	200µA @ 5V	0°C ~ 70°C	Leap Year, NVSRAM, Square Wave Output	Active	ROHS3 Compliant
DS1339AU+T	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	1.71V ~ 5.5V	1.3V ~ 3.7V	200µA @ 1.71V ~ 5.5V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Active	ROHS3 Compliant
DS1340Z-18+	Analog Devices Inc./Maxim Integrated	8-SOIC (0.154", 3.90mm)	I2C, 2-Wire Serial	1.71V ~ 5.5V	1.3V ~ 3.7V	100µA @ 1.89V	-40°C ~ 85°C	Leap Year, Trickle-Charger	Active	ROHS3 Compliant
DS1339C-33#T&R	Analog Devices Inc./Maxim Integrated	16-SOIC (0.295", 7.50mm)	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 3.7V	200µA @ 5.5V	-40°C ~ 85°C	Alarm, Leap Year, Square Wave Output, Trickle-Charger	Active	ROHS3 Compliant

Engineering Selection Recommendations

Direct Replacement (Preferred): PCF2129AT/2,518 is the primary substitute for PCF2129AT/1,512. Both components share identical electrical specifications, package form factor (20-SOIC), and feature set. The primary distinction is product status: PCF2129AT/2,518 is Active, ensuring continued availability and supply chain stability. Both are ROHS3 compliant with equivalent moisture sensitivity levels.

Package-Compatible Alternatives (16-SOIC): DS1337C# and DS1339C-33#T&R maintain the same 16-SOIC package width (0.295", 7.50mm) as the original part, though with reduced pin count. Both support the required I2C interface, Clock/Calendar functionality, and -40°C ~ 85°C operating range. DS1337C# offers superior low-voltage performance (0.6µA timekeeping current at 1.3V ~ 1.8V), while DS1339C-33#T&R includes trickle-charger functionality. Both are Active products with ROHS3 compliance.

Compact Package Alternatives (8-SOIC / 8-TSSOP): For applications where board space is constrained, DS1340Z-3+, DS1340Z-18+, 1338-31DCGI8, DS1339AU+T, DS1339U-33+T&R, and 1339-31DVGI8 provide functional RTC capability in smaller packages. These alternatives require PCB redesign due to different pin configurations and package dimensions. DS1340Z-18+ and DS1340Z-3+ support the full -40°C ~ 85°C temperature range with low-voltage operation (1.71V minimum). 1338-31DCGI8 includes NVSRAM (56B) for additional data storage.

Voltage Supply Considerations: The original PCF2129AT/1,512 operates at 1.8V ~ 4.2V. Substitutes with higher minimum voltage requirements (DS1307Z+ at 4.5V, 1338-31DCGI8 and 1339-31DVGI8 at 3.3V) are suitable only for designs with compatible supply rails. DS1340Z-18+, DS1340Z-3+, and DS1339AU+T support the full low-voltage range (1.71V ~ 2.7V minimum), ensuring compatibility with battery-backed and ultra-low-power applications.

Compliance and Certification: All substitute parts listed are ROHS3 compliant and REACH unaffected, matching the original component's regulatory status. Moisture sensitivity levels vary (MSL 1 for most Analog Devices parts, MSL 3 for Renesas 1339-31DVGI8), which may affect storage and handling requirements.

Frequently Asked Questions (FAQ)

Q: Can PCF2129AT/2,518 be used as a direct drop-in replacement for PCF2129AT/1,512? A: Yes. PCF2129AT/2,518 is electrically and functionally identical to PCF2129AT/1,512, with the same 20-SOIC package, I2C interface, supply voltage range (1.8V ~ 4.2V), and feature set. The only difference is product status (Active vs. Obsolete) and packaging format (Digi-Reel vs. standard packaging).

Q: What are the key differences between 20-SOIC and 16-SOIC package alternatives? A: Both maintain the same 0.295" (7.50mm) width, but 16-SOIC has 16 pins versus 20 pins in the original package. This requires PCB redesign and pin reassignment. However, the I2C interface (SDA/SCL) remains compatible, and all listed 16-SOIC alternatives support the same Clock/Calendar functionality.

Q: Why do some substitutes have higher timekeeping current consumption? A: Timekeeping current varies by design and manufacturing process. DS1307Z+ and DS1339 variants consume 200µA at 5V, while the original PCF2129AT/1,512 consumes only 1.5µA at 3.3V. For battery-backed applications requiring ultra-low power, DS1340Z-18+ (100µA @ 1.89V) or DS1337C# (0.6µA @ 1.3V ~ 1.8V) are preferred.

Q: Are all substitute parts suitable for -40°C ~ 85°C industrial temperature range? A: Most substitutes support -40°C ~ 85°C. The exception is DS1307Z+, which operates only at 0°C ~ 70°C, making it unsuitable for industrial or extended temperature applications.

Q: What is the impact of different supply voltage ranges on substitution? A: The original part operates at 1.8V ~ 4.2V. Substitutes with higher minimum voltage (e.g., 1338-31DCGI8 at 3.3V minimum) cannot be used in designs requiring 1.8V operation. Conversely, substitutes with lower minimum voltage (e.g., DS1340Z-18+ at 1.71V) are compatible with all original supply rails.

Q: Do all substitutes support both 12-hour and 24-hour time formats? A: The original PCF2129AT/1,512 supports both 12/24-hour formats. DS1340Z-3+ and DS1340Z-18+ support 24-hour format only. For applications requiring 12-hour format capability, use PCF2129AT/2,518, DS1337C#, DS1339 variants, 1338-31DCGI8, or 1339-31DVGI8.

Q: What is the significance of NVSRAM in 1338-31DCGI8? A: NVSRAM (Non-Volatile Static RAM) provides 56 bytes of additional non-volatile memory for data storage beyond the RTC registers. This is useful for applications requiring persistent data logging or configuration storage. The original PCF2129AT/1,512 does not include this feature.

Q: How does moisture sensitivity level (MSL) affect component handling? A: MSL 3 (168 hours) requires storage in dry conditions and limits the time between package opening and soldering. MSL 1 (Unlimited) has no time restrictions. Most Analog Devices substitutes are MSL 1, while Renesas 1339-31DVGI8 is MSL 3, matching the original part's handling requirements.

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