PCF2129AT/1,518 Equivalent & Substitute Parts

Part Overview

The PCF2129AT/1,518 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, featuring I2C 2-Wire Serial interface in a 20-SOIC package. Manufactured by NXP USA Inc., this component provides timekeeping with alarm, leap year support, square wave output, and watchdog timer capabilities. The part is currently listed as obsolete, necessitating identification of active equivalent and substitute components that maintain functional and electrical compatibility for new designs and production continuity.

Key Parameters

Parameter	PCF2129AT/1,518
Manufacturer	NXP USA Inc.
Product Status	Obsolete
Package / Case	20-SOIC (0.295", 7.50mm Width)
Interface	I2C, 2-Wire Serial
Type	Clock/Calendar
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
RoHS Status	ROHS3 Compliant
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitution of the PCF2129AT/1,518 is determined by the following critical parameters:

Primary Compatibility Criteria:

Interface type: I2C, 2-Wire Serial
Functional type: Clock/Calendar RTC
Operating temperature range: -40°C ~ 85°C
Supply voltage compatibility: Overlap with 1.8V ~ 4.2V range
Time and date format support: HH:MM:SS (12/24 hr) and YY-MM-DD-dd

Secondary Considerations:

Package form factor (surface mount vs. through-hole affects PCB layout)
Current consumption during timekeeping operation
Feature set alignment (alarm, leap year, watchdog timer)
RoHS and regulatory compliance status

Substitute parts are grouped into two categories: direct package equivalents (20-SOIC surface mount) and functional alternatives with different package formats. Direct equivalents maintain identical pinout and package dimensions. Functional alternatives provide equivalent RTC capabilities but may require PCB redesign due to different package types (8-SOIC, 8-TSSOP, 8-DIP, 8-WCDFN).

Parameter Comparison

Part Number	Manufacturer	Package / Case	Interface	Voltage - Supply	Current - Timekeeping (Max)	Operating Temperature	Product Status	RoHS Status
PCF2129AT/1,518	NXP USA Inc.	20-SOIC (0.295", 7.50mm)	I2C, 2-Wire Serial	1.8V ~ 4.2V	1.5µA @ 3.3V	-40°C ~ 85°C	Obsolete	ROHS3 Compliant
PCF2129AT/2,518	NXP Semiconductors	20-SOIC (0.295", 7.50mm)	I2C, 2-Wire Serial	1.8V ~ 4.2V	1.5µA @ 3.3V	-40°C ~ 85°C	Active	ROHS3 Compliant
1338-31DCGI	Renesas Electronics Corporation	8-SOIC (0.154", 3.90mm)	I2C, 2-Wire Serial	3.3V ~ 5.5V	5µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
AB-RTCMC-32.768KHZ-AIGZ-S7-T	Abracon LLC	8-WCDFN	I2C, 2-Wire Serial	1V ~ 4.4V	0.4µA ~ 0.95µA @ 1V ~ 4.4V	-40°C ~ 85°C	Active	ROHS3 Compliant
BU9873FVT-GE2	Rohm Semiconductor	8-TSSOP (0.173", 4.40mm)	I2C, 2-Wire Serial	1.8V ~ 5.5V	1µA ~ 1.35µA @ 3V ~ 5.5V	-40°C ~ 85°C	Not For New Designs	ROHS3 Compliant
DS1307N+	Analog Devices Inc./Maxim Integrated	8-DIP (0.300", 7.62mm)	I2C, 2-Wire Serial	4.5V ~ 5.5V	200µA @ 5V	-40°C ~ 85°C	Active	ROHS3 Compliant
DS1308U-33+T	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	3V ~ 5.5V	125µA ~ 200µA @ 3V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
DS1338U-33+	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	3V ~ 5.5V	125µA ~ 200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
DS1338Z-3+	Analog Devices Inc./Maxim Integrated	8-SOIC (0.154", 3.90mm)	I2C, 2-Wire Serial	2.7V ~ 5.5V	200µA @ 3.3V	-40°C ~ 85°C	Active	ROHS3 Compliant
DS1339BU+T	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	1.71V ~ 5.5V	200µA @ 1.71V ~ 5.5V	-40°C ~ 85°C	Active	ROHS3 Compliant
DS1339U-3+T&R	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP (0.118", 3.00mm)	I2C, 2-Wire Serial	2.7V ~ 5.5V	150µA @ 3.3V	-40°C ~ 85°C	Active	ROHS3 Compliant

Engineering Selection Recommendations

Direct Package Equivalent (Recommended for Minimal Redesign):

PCF2129AT/2,518 is the primary substitute for PCF2129AT/1,518. Both components share identical electrical specifications, package format (20-SOIC), and functional features. The PCF2129AT/2,518 is currently in active production status with ROHS3 compliance, making it suitable for immediate replacement without PCB layout modifications.

Active Alternatives with Package Redesign Requirement:

For applications where package redesign is acceptable, the following active components provide equivalent RTC functionality:

AB-RTCMC-32.768KHZ-AIGZ-S7-T (Abracon LLC): Offers the lowest timekeeping current consumption (0.4µA ~ 0.95µA) and widest supply voltage range (1V ~ 4.4V), suitable for ultra-low-power applications. Requires PCB redesign due to 8-WCDFN package format.
DS1339BU+T and DS1339U-3+T&R (Analog Devices Inc./Maxim Integrated): Provide extended supply voltage range (1.71V ~ 5.5V and 2.7V ~ 5.5V respectively) with alarm and trickle-charger features. Available in 8-TSSOP/8-MSOP packages.
DS1338Z-3+ (Analog Devices Inc./Maxim Integrated): Offers 56B NVSRAM and square wave output in 8-SOIC package with supply range 2.7V ~ 5.5V.

Components Not Recommended for New Designs:

BU9873FVT-GE2 (Rohm Semiconductor) carries "Not For New Designs" status and should be avoided for new product development despite functional compatibility.

Compliance Verification:

All recommended substitutes maintain ROHS3 compliance and REACH unaffected status, consistent with the original PCF2129AT/1,518 regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can PCF2129AT/2,518 be used as a direct replacement for PCF2129AT/1,518?

A: Yes. PCF2129AT/2,518 is a direct functional and electrical equivalent with identical package, pinout, voltage specifications (1.8V ~ 4.2V), timekeeping current (1.5µA @ 3.3V), and feature set. The primary difference is product status: PCF2129AT/2,518 is active while PCF2129AT/1,518 is obsolete. No PCB modifications are required.

Q: What is the key difference between the 20-SOIC package PCF2129AT/2,518 and the 8-SOIC package alternatives?

A: The 20-SOIC package provides 20 pins with additional functionality and memory capacity compared to 8-pin variants. Direct package substitution requires identical pin count and spacing. The 8-SOIC alternatives (1338-31DCGI, DS1338Z-3+) require PCB redesign but provide equivalent RTC core functionality. Pin mapping and feature availability differ between packages.

Q: Which substitute offers the lowest power consumption?

A: AB-RTCMC-32.768KHZ-AIGZ-S7-T provides the lowest timekeeping current at 0.4µA ~ 0.95µA across its supply range (1V ~ 4.4V). This component is optimal for battery-powered applications requiring extended operational life. However, it uses an 8-WCDFN package requiring PCB redesign.

Q: Are all substitute parts RoHS compliant?

A: Yes. All listed substitute components maintain ROHS3 compliance and REACH unaffected status, matching the regulatory compliance of the original PCF2129AT/1,518.

Q: What supply voltage range should I verify when selecting a substitute?

A: The original PCF2129AT/1,518 operates at 1.8V ~ 4.2V. Substitutes must support this range or a compatible overlap. AB-RTCMC-32.768KHZ-AIGZ-S7-T (1V ~ 4.4V) and DS1339BU+T (1.71V ~ 5.5V) provide full compatibility. DS1307N+ (4.5V ~ 5.5V) is incompatible with the lower voltage requirement.

Q: Can I use DS1307N+ as a substitute?

A: DS1307N+ is not recommended as a direct substitute. Its supply voltage range (4.5V ~ 5.5V) does not overlap with the PCF2129AT/1,518 requirement (1.8V ~ 4.2V). Additionally, it uses an 8-DIP through-hole package incompatible with surface-mount PCB designs. Current consumption is significantly higher (200µA @ 5V vs. 1.5µA @ 3.3V).

Q: What is the significance of "Not For New Designs" status on BU9873FVT-GE2?

A: This designation indicates the manufacturer recommends against using this component in new product development. While functionally compatible, it may have limited availability or planned discontinuation. Active alternatives should be prioritized for new designs.

Q: Do all substitutes support both 12-hour and 24-hour time formats?

A: The PCF2129AT/1,518 and most listed substitutes support HH:MM:SS in both 12/24-hour formats. AB-RTCMC-32.768KHZ-AIGZ-S7-T specifies HH:MM:SS:hh (24-hour only). Verify time format requirements for your application before selection.

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