PCF2127AT/2Y Equivalent & Substitute Parts

Part Overview

The PCF2127AT/2Y is an NXP USA Inc. Real Time Clock (RTC) IC with integrated clock/calendar functionality, 512B memory, and I2C serial interface. This 20-SOIC package device operates across 1.8V to 4.2V supply range with ultra-low timekeeping current of 1.5µA at 3.3V. The part is currently Active in product status and ROHS3 compliant.

Substitute parts are necessary when the PCF2127AT/2Y becomes unavailable, when alternative packaging or performance characteristics better suit specific application requirements, or when design flexibility demands components with different feature sets while maintaining core RTC functionality.

Key Parameters

Parameter	PCF2127AT/2Y
Manufacturer	NXP USA Inc.
Package / Case	20-SOIC (0.295", 7.50mm Width)
Memory Size	512B
Interface	I2C, 2-Wire Serial
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, SRAM, TCXO/Crystal, Watchdog Timer
RoHS Status	ROHS3 Compliant
Product Status	Active

Substitute Part Grouping Explanation

Substitution logic for the PCF2127AT/2Y is based on the following critical parameters:

Interface Compatibility: All substitute parts must support I2C 2-Wire Serial protocol to maintain firmware and PCB layout compatibility.

Operating Voltage Range: Substitute parts must operate within or encompass the 1.8V to 4.2V supply range. Parts with wider voltage ranges (e.g., 1.71V ~ 5.5V) are acceptable as they cover the required operating window.

Package Compatibility: The 20-SOIC package is specific to the PCF2127AT/2Y. Substitutes with different packages (8-TSSOP, 8-MSOP, 8-SOIC, 16-SOIC, Module) require PCB redesign and are classified as functional alternatives rather than direct pin-compatible replacements.

Memory Size: The 512B memory is a defining characteristic. Substitutes with 512B, 64B, 56B, or 2B memory represent different functional classes. Smaller memory devices may not support equivalent SRAM capacity.

Timekeeping Current: The PCF2127AT/2Y draws 1.5µA at 3.3V. Substitutes with lower timekeeping current (0.29µA ~ 0.33µA, 0.6µA, 1.2µA) offer improved battery life. Higher current devices (4µA ~ 6µA, 70µA, 100µA, 125µA ~ 200µA, 130µA ~ 200µA) represent different power classes.

Temperature Range: All listed substitutes maintain the -40°C to 85°C operating range, ensuring thermal compatibility.

Feature Set: The PCF2127AT/2Y includes Alarm, Leap Year, Square Wave Output, SRAM, TCXO/Crystal, and Watchdog Timer. Substitutes may omit certain features (e.g., no Watchdog Timer, no TCXO/Crystal) or add features (e.g., Trickle Charge, Unique ID).

Parameter Comparison

Part Number	Manufacturer	Package	Memory	Interface	Supply Voltage	Battery Voltage	Timekeeping Current	Temp Range	Product Status
PCF2127AT/2Y	NXP USA Inc.	20-SOIC	512B	I2C, 2-Wire	1.8V ~ 4.2V	1.8V ~ 4.2V	1.5µA @ 3.3V	-40°C ~ 85°C	Active
AB-RTCMC-32.768KHZ-IBO5-S3-T	Abracon LLC	Module	512B	I2C, 2-Wire	1.5V ~ 3.6V	1.4V ~ 3.6V	0.29µA ~ 0.33µA @ 1.8V ~ 3V	-40°C ~ 85°C	Not For New Designs
DS1308U-33+T	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP	56B	I2C, 2-Wire	3V ~ 5.5V	1.3V ~ 5.5V	125µA ~ 200µA @ 3V ~ 5.5V	-40°C ~ 85°C	Active
DS1337U+T&R	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP	—	I2C, 2-Wire	1.8V ~ 5.5V	—	0.6µA @ 1.3V ~ 1.8V	-40°C ~ 85°C	Active
DS1338U-18+T&R	Analog Devices Inc./Maxim Integrated	8-TSSOP, 8-MSOP	56B	I2C, 2-Wire	1.71V ~ 5.5V	1.3V ~ 3.7V	100µA @ 1.89V	-40°C ~ 85°C	Active
DS3231M+	Analog Devices Inc./Maxim Integrated	16-SOIC	—	I2C, 2-Wire	2.3V ~ 5.5V	2.3V ~ 5.5V	130µA ~ 200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	Active
ISL1208IRT8Z-TK	Renesas Electronics Corporation	8-WDFN Exposed Pad	2B	I2C, 2-Wire	2.7V ~ 5.5V	1.8V ~ 5.5V	4µA ~ 6µA @ 3V ~ 5V	-40°C ~ 85°C	Obsolete
ISL1208IU8Z-TK	Renesas Electronics Corporation	8-TSSOP, 8-MSOP	2B	I2C, 2-Wire	2.7V ~ 5.5V	1.8V ~ 5.5V	4µA ~ 6µA @ 3V ~ 5V	-40°C ~ 85°C	Active
M41T11M6F	STMicroelectronics	8-SOIC	56B	I2C, 2-Wire	2V ~ 5.5V	2.5V ~ 4.6V	70µA @ 2V ~ 5.5V	-40°C ~ 85°C	Active
MCP79400-I/ST	Microchip Technology	8-TSSOP	64B	I2C, 2-Wire	1.8V ~ 5.5V	1.3V ~ 5.5V	1.2µA (Typ) @ 3.3V	-40°C ~ 85°C	Active
MCP79402-I/MS	Microchip Technology	8-TSSOP, 8-MSOP	64B	I2C, 2-Wire	1.8V ~ 5.5V	1.3V ~ 5.5V	1.2µA (Typ) @ 3.3V	-40°C ~ 85°C	Active

Engineering Selection Recommendations

Direct Pin-Compatible Replacement: No substitute part listed maintains the 20-SOIC package of the PCF2127AT/2Y. All alternatives require PCB redesign.

Functional Equivalents with Active Status: The following parts are currently Active and suitable for new designs:

DS1337U+T&R and DS1338U-18+T&R (Analog Devices Inc./Maxim Integrated) offer I2C compatibility and extended voltage ranges. DS1337U+T&R provides ultra-low timekeeping current (0.6µA) but lacks specified memory. DS1338U-18+T&R includes 56B memory and operates across 1.71V ~ 5.5V supply range.

ISL1208IU8Z-TK (Renesas Electronics Corporation) is Active with I2C interface, 2B memory, and 4µA ~ 6µA timekeeping current in 8-TSSOP package.

MCP79400-I/ST and MCP79402-I/MS (Microchip Technology) both provide 64B memory, 1.2µA typical timekeeping current at 3.3V, and 1.8V ~ 5.5V supply range. MCP79402-I/MS is available in 8-MSOP package.

M41T11M6F (STMicroelectronics) is Active with 56B memory, I2C interface, and 70µA timekeeping current in 8-SOIC package.

DS3231M+ (Analog Devices Inc./Maxim Integrated) is Active in 16-SOIC package with I2C interface but requires higher minimum supply voltage (2.3V) and higher timekeeping current (130µA ~ 200µA).

Parts Not Recommended for New Designs: AB-RTCMC-32.768KHZ-IBO5-S3-T (Abracon LLC) carries "Not For New Designs" status despite matching 512B memory and offering superior timekeeping current (0.29µA ~ 0.33µA). ISL1208IRT8Z-TK (Renesas Electronics Corporation) is Obsolete.

Compliance: All Active substitute parts maintain ROHS3 compliance and REACH Unaffected status, matching the PCF2127AT/2Y regulatory profile.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part in an 8-pin package as a direct replacement for the PCF2127AT/2Y in a 20-SOIC package?

A: No. The PCF2127AT/2Y uses a 20-SOIC package with specific pinout. Substitutes in 8-TSSOP, 8-MSOP, 8-SOIC, or 8-WDFN packages have different pin configurations and require PCB redesign. Package compatibility is not interchangeable.

Q: Which substitute offers the lowest timekeeping current?

A: The AB-RTCMC-32.768KHZ-IBO5-S3-T (Abracon LLC) draws 0.29µA ~ 0.33µA at 1.8V ~ 3V, significantly lower than the PCF2127AT/2Y at 1.5µA @ 3.3V. However, this part carries "Not For New Designs" status. Among Active parts, DS1337U+T&R offers 0.6µA @ 1.3V ~ 1.8V.

Q: What is the memory difference between the PCF2127AT/2Y and substitute parts?

A: The PCF2127AT/2Y provides 512B memory. Substitutes vary: AB-RTCMC-32.768KHZ-IBO5-S3-T matches at 512B; MCP79400-I/ST and MCP79402-I/MS provide 64B; DS1308U-33+T and DS1338U-18+T&R provide 56B; ISL1208IRT8Z-TK and ISL1208IU8Z-TK provide 2B; DS1337U+T&R and DS3231M+ specify no memory. Smaller memory devices limit SRAM capacity for application data storage.

Q: Are all substitute parts I2C compatible with the PCF2127AT/2Y?

A: Yes. All listed substitutes support I2C 2-Wire Serial interface, ensuring protocol compatibility. However, different memory sizes, feature sets, and register maps may require firmware modifications.

Q: Which substitute parts are suitable for battery-backed operation?

A: All substitutes support battery backup. The PCF2127AT/2Y operates on 1.8V ~ 4.2V battery supply. DS1337U+T&R does not specify battery voltage. AB-RTCMC-32.768KHZ-IBO5-S3-T operates on 1.4V ~ 3.6V battery supply. MCP79400-I/ST, MCP79402-I/MS, and DS1338U-18+T&R support 1.3V ~ 5.5V battery range, providing wider flexibility.

Q: Can I substitute the PCF2127AT/2Y with a part that has a higher supply voltage range?

A: Yes, if the substitute's supply voltage range encompasses the PCF2127AT/2Y's 1.8V ~ 4.2V window. For example, DS1338U-18+T&R (1.71V ~ 5.5V) and MCP79400-I/ST (1.8V ~ 5.5V) are acceptable. However, verify that the application's power supply design does not exceed the substitute's maximum voltage rating.

Q: What features does the PCF2127AT/2Y have that may not be present in all substitutes?

A: The PCF2127AT/2Y includes Alarm, Leap Year, Square Wave Output, SRAM, TCXO/Crystal, and Watchdog Timer. Not all substitutes include all features. For example, DS1337U+T&R and DS3231M+ omit SRAM and Watchdog Timer specifications. ISL1208IRT8Z-TK and ISL1208IU8Z-TK omit Square Wave Output and Watchdog Timer. Verify feature requirements before substitution.

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