PCA2125TS/1,118 Real Time Clock IC – Equivalent & Substitute Parts

Part Overview

The PCA2125TS/1,118 is a Real Time Clock (RTC) IC with Clock/Calendar functionality, manufactured by NXP USA Inc. in a 14-TSSOP surface mount package. This device provides SPI interface communication, alarm capability, leap year support, square wave output, and watchdog timer functionality across a wide supply voltage range of 1.6V to 5.5V. The product is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	Value
Manufacturer Part Number	PCA2125TS/1,118
Manufacturer	NXP USA Inc.
Product Category	Clock/Timing – RTC Clock/Calendar
Interface	SPI
Package Type	14-TSSOP (0.173", 4.40mm Width)
Voltage Supply Range	1.6V ~ 5.5V
Current – Timekeeping (Max)	1.8µA @ 2V ~ 5V
Operating Temperature	-40°C ~ 125°C
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Key Features	Alarm, Leap Year, Square Wave Output, Watchdog Timer
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the PCA2125TS/1,118 is determined by the following critical parameters:

Interface Compatibility: All substitute parts must support SPI communication protocol to maintain firmware and hardware interface compatibility.

Voltage Supply Range: The original part operates from 1.6V to 5.5V. Substitute parts must support overlapping or equivalent supply voltage ranges to function in the same circuit topology.

Package Type & Mounting: Surface mount packages are required. While package footprints may differ (14-TSSOP, 14-SOIC, 16-QFN, 10-MSOP), PCB layout redesign is acceptable for substitution.

Functional Features: Core RTC functionality including clock/calendar operation, alarm capability, and leap year support must be present. Square wave output and watchdog timer are desirable but not mandatory for basic RTC operation.

Operating Temperature Range: The original part supports -40°C to 125°C. Substitute parts with -40°C to 85°C range are acceptable for most industrial applications.

Compliance & Status: All substitute parts must maintain ROHS3 compliance and active product status to ensure long-term availability and regulatory compliance.

Parameter Comparison

Parameter	PCA2125TS/1,118	AB1815-T3	DS1391U-3+	DS3234SN#T&R	M41T93RMY6F	MCP795W12-I/SL	MCP79521T-I/MS
Manufacturer	NXP USA Inc.	Abracon LLC	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	STMicroelectronics	Microchip Technology	Microchip Technology
Interface	SPI	SPI	SPI	SPI	SPI	SPI	SPI
Package Type	14-TSSOP	16-VFQFN	10-TFSOP/MSOP	20-SOIC	18-SOX/SOIC	14-SOIC	10-TFSOP/MSOP
Voltage Supply Range	1.6V ~ 5.5V	1.7V ~ 3.6V	2.7V ~ 3.3V	2V ~ 5.5V	2.7V ~ 5.5V	1.8V ~ 3.6V	1.8V ~ 3.6V
Operating Temperature	-40°C ~ 125°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
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS:hh	HH:MM:SS:hh (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS:hh (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
Alarm Feature	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Leap Year Support	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Square Wave Output	Yes	No	Yes	Yes	Yes	Yes	Yes
Watchdog Timer	Yes	Yes	No	No	Yes	Yes	No
Memory Size	Not specified	256B	Not specified	256B	7B	64B	64B
Current – Timekeeping (Max)	1.8µA @ 2V ~ 5V	0.17µA ~ 0.22µA @ 1.8V ~ 3V	125µA @ 2.7V ~ 3.3V	120µA ~ 160µA @ 3.63V ~ 5.5V	10µA @ 5.5V	1µA @ 1.8V ~ 5.5V	1µA @ 1.8V ~ 3.6V
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active	Active	Active	Active	Active	Active

Engineering Selection Recommendations

Primary Substitutes for Direct Replacement:

MCP795W12-I/SL (Microchip Technology) is the closest functional equivalent. It maintains the 14-pin package footprint (14-SOIC vs. 14-TSSOP), SPI interface, and includes all core features: alarm, leap year, square wave output, watchdog timer, and SRAM. Supply voltage range is 1.8V to 3.6V, which covers most 3.3V and lower voltage applications. Product status is active with full ROHS3 compliance.

DS3234SN#T&R (Analog Devices Inc./Maxim Integrated) provides extended supply voltage range (2V to 5.5V) matching the original part's upper limit. It includes 256B SRAM, square wave output, and alarm functionality. The 20-SOIC package requires PCB layout modification. Current consumption is higher at 120µA to 160µA. Product status is active with ROHS3 compliance.

Alternative Substitutes for Specific Applications:

AB1815-T3 (Abracon LLC) offers the lowest timekeeping current consumption (0.17µA to 0.22µA) and includes 256B SRAM with trickle-charger functionality. Supply voltage is limited to 1.7V to 3.6V. The 16-VFQFN package requires PCB redesign. Product status is active with ROHS3 compliance.

M41T93RMY6F (STMicroelectronics) supports extended supply voltage (2.7V to 5.5V) and includes integrated crystal with 18-SOX package. Timekeeping current is 10µA at 5.5V. Product status is active with ROHS3 compliance.

MCP79521T-I/MS (Microchip Technology) provides low timekeeping current (1µA) and includes EEPROM with unique ID feature in 10-MSOP package. Supply voltage range is 1.8V to 3.6V. Product status is active with ROHS3 compliance.

DS1391U-3+ and DS1391U-3+T&R (Analog Devices Inc./Maxim Integrated) offer compact 10-TFSOP/MSOP packages with alarm and square wave output. Supply voltage is limited to 2.7V to 3.3V. Timekeeping current is 125µA. Product status is active with ROHS3 compliance.

All substitute parts maintain ROHS3 compliance and active product status, ensuring regulatory compliance and long-term availability for production and design support.

Frequently Asked Questions (FAQ)

Q: Can MCP795W12-I/SL directly replace PCA2125TS/1,118 without PCB modification?

A: MCP795W12-I/SL uses 14-SOIC package versus the original 14-TSSOP package. While both are 14-pin surface mount packages, the pin pitch and body dimensions differ. PCB footprint modification is required, though the pin count and SPI interface remain compatible.

Q: What is the key difference between AB1815-T3 and MCP795W12-I/SL?

A: AB1815-T3 offers significantly lower timekeeping current (0.17µA to 0.22µA) compared to MCP795W12-I/SL (1µA), making it superior for battery-backed applications. However, AB1815-T3 supply voltage is limited to 1.7V to 3.6V, while MCP795W12-I/SL supports 1.8V to 3.6V. AB1815-T3 uses 16-VFQFN package requiring greater PCB redesign effort.

Q: Why does DS3234SN#T&R have higher current consumption than the original part?

A: DS3234SN#T&R timekeeping current is specified as 120µA to 160µA at 3.63V to 5.5V, compared to the original 1.8µA at 2V to 5V. This reflects different measurement conditions and the inclusion of integrated TCXO/crystal oscillator, which contributes to higher current draw but improves frequency stability.

Q: Which substitute part is best for low-power battery-backed applications?

A: AB1815-T3 provides the lowest timekeeping current at 0.17µA to 0.22µA, making it optimal for battery-backed RTC applications. MCP79521T-I/MS and MCP795W12-I/SL also offer low current at 1µA, providing alternative options with different package configurations.

Q: Are all substitute parts compatible with 5V supply voltage?

A: No. Only DS3234SN#T&R and M41T93RMY6F support the full 5V supply range (2V to 5.5V and 2.7V to 5.5V respectively). Most other substitutes are limited to 3.6V maximum. Verify supply voltage requirements before selection.

Q: What is the impact of package change on design implementation?

A: Package changes require PCB footprint redesign and potential layout modifications. 14-pin packages (14-SOIC, 14-TSSOP) require minimal redesign. Smaller packages (10-MSOP, 16-QFN) require greater layout effort. Larger packages (18-SOX, 20-SOIC) may require additional board space. Firmware compatibility remains unchanged as all parts use SPI interface.

Q: Do all substitute parts support 12/24-hour time format?

A: Most substitute parts support 12/24-hour format. M41T93RMY6F and M41T93SQA6F support 24-hour format only. AB1815-T3 supports HH:MM:SS:hh format. Verify time format requirements against application specifications.

Q: Which substitute offers the best balance of compatibility and availability?

A: MCP795W12-I/SL provides optimal balance with 14-pin package (minimal PCB redesign), active product status, full feature set (alarm, leap year, square wave output, watchdog timer), and high inventory availability (1068 pcs). Supply voltage range 1.8V to 3.6V covers most 3.3V applications.

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