MCP79401T-I/ST Real Time Clock (RTC) IC Equivalent & Substitute Parts

Part Overview

The MCP79401T-I/ST is an active Real Time Clock (RTC) IC manufactured by Microchip Technology, designed for Clock/Calendar applications with I2C 2-Wire Serial interface. This device provides timekeeping functionality with 64 bytes of SRAM, alarm capability, leap year support, and square wave output in an 8-TSSOP surface mount package. The part operates across a wide supply voltage range of 1.8V to 5.5V with battery backup support from 1.3V to 5.5V, making it suitable for diverse embedded system applications. Substitute parts are identified based on matching functional categories, interface protocols, operating temperature ranges, and package compatibility within the Clock/Calendar RTC product family.

Key Parameters

Parameter	MCP79401T-I/ST
Manufacturer	Microchip Technology
Category	Clock/Timing
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Memory Size	64B
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Voltage - Supply	1.8V ~ 5.5V
Voltage - Supply, Battery	1.3V ~ 5.5V
Current - Timekeeping (Max)	1.2µA (Typ) @ 3.3V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	8-TSSOP (0.173", 4.40mm Width)
Features	Alarm, Leap Year, Square Wave Output, SRAM, Unique ID
Product Status	Active
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts for the MCP79401T-I/ST are selected based on the following critical parameters that determine functional compatibility:

Primary Substitution Criteria:

Category: Clock/Timing, Type: Clock/Calendar
Interface: I2C, 2-Wire Serial protocol
Operating Temperature Range: -40°C ~ 85°C
Mounting Type: Surface Mount
Product Status: Active
RoHS3 Compliance and MSL Level 1

Secondary Compatibility Factors:

Time Format: HH:MM:SS with 12/24 hour support
Date Format: YY-MM-DD-dd
Supply Voltage Overlap: Minimum 1.8V to 5.5V range or compatible subset
Battery Backup Support: 1.3V minimum threshold
Package Type: 8-pin surface mount variants (8-TSSOP, 8-SOIC, 8-MSOP, 8-WDFN)

Substitute parts are grouped into two categories based on package compatibility: 8-pin SOIC/MSOP variants and 8-pin TSSOP/WDFN variants. Parts with 16-pin packages are included where feature parity and interface compatibility are maintained.

Parameter Comparison

Part Number	Manufacturer	Interface	Voltage Supply	Battery Voltage	Time Format	Date Format	Operating Temp	Package	Features
MCP79401T-I/ST	Microchip Technology	I2C, 2-Wire Serial	1.8V ~ 5.5V	1.3V ~ 5.5V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-TSSOP	Alarm, Leap Year, Square Wave Output, SRAM, Unique ID
1338-31DCGI	Renesas Electronics Corporation	I2C, 2-Wire Serial	3.3V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-SOIC	Leap Year, NVSRAM, Square Wave Output
BQ32002DR	Texas Instruments	I2C, 2-Wire Serial	3V ~ 3.6V	1.4V ~ 3.6V	HH:MM:SS (24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-SOIC	Leap Year, Square Wave Output, Trickle-Charger
DS1307ZN+T&R	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	4.5V ~ 5.5V	2V ~ 4.6V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-SOIC	Leap Year, NVSRAM, Square Wave Output
DS1337S+	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	1.8V ~ 5.5V	Not Specified	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-SOIC	Alarm, Leap Year, Square Wave Output
DS1338C-3#	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	16-SOIC	Leap Year, NVSRAM, Square Wave Output
DS1338Z-18+	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	1.71V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-SOIC	Leap Year, NVSRAM, Square Wave Output
DS1339U-3+T&R	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-TSSOP, 8-MSOP	Alarm, Leap Year, Square Wave Output, Trickle-Charger
DS1339U-33+	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-TSSOP, 8-MSOP	Alarm, Leap Year, Square Wave Output, Trickle-Charger
DS1340Z-33+	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 5.5V	HH:MM:SS (24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-SOIC	Leap Year, Trickle-Charger
DS1341T+T&R	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	1.8V ~ 5.5V	Not Specified	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	-40°C ~ 85°C	8-WDFN Exposed Pad	Alarm, Leap Year, Square Wave Output

Engineering Selection Recommendations

Direct Package-Compatible Substitutes (8-TSSOP/MSOP):

DS1339U-3+T&R and DS1339U-33+ are the closest functional equivalents to MCP79401T-I/ST, offering identical package form factors (8-TSSOP, 8-MSOP), matching I2C interface, 12/24-hour time format, and operating temperature range. Both parts are Active status with ROHS3 compliance and MSL Level 1. The DS1339U series includes alarm functionality and trickle-charger features. Supply voltage ranges are 2.7V ~ 5.5V (DS1339U-3+T&R) and 2.97V ~ 5.5V (DS1339U-33+), which overlap the MCP79401T-I/ST range above 2.7V. Battery backup support is 1.3V ~ 3.7V for both variants.

DS1341T+T&R provides an alternative in 8-WDFN Exposed Pad package with matching 1.8V ~ 5.5V supply voltage range and full feature set including alarm and leap year support. This part is suitable for applications requiring compact form factor with thermal management capability.

8-SOIC Package Alternatives:

DS1338Z-18+ offers the widest supply voltage compatibility (1.71V ~ 5.5V) among 8-SOIC variants, with battery backup from 1.3V ~ 3.7V. This part maintains 12/24-hour time format, NVSRAM, and square wave output features. DS1337S+ provides 1.8V ~ 5.5V supply range with alarm capability but lacks specified battery voltage support.

DS1307ZN+T&R and 1338-31DCGI are suitable for applications operating above 3.3V, with DS1307ZN+T&R requiring minimum 4.5V supply and 1338-31DCGI requiring 3.3V minimum.

BQ32002DR is restricted to 3V ~ 3.6V supply range and 24-hour time format only, limiting its applicability to systems with fixed 3.3V supply and 24-hour timekeeping requirements.

16-SOIC Package Option:

DS1338C-3# provides expanded functionality in 16-SOIC package with 2.7V ~ 5.5V supply range and 1.3V ~ 3.7V battery backup. This part is suitable for applications requiring additional I/O or memory expansion within the same footprint class.

All substitute parts maintain Active product status, ROHS3 compliance, and MSL Level 1 rating, ensuring long-term availability and environmental compliance equivalent to the original part.

Frequently Asked Questions (FAQ)

Q: Can DS1339U-3+T&R directly replace MCP79401T-I/ST in existing PCB designs?

A: DS1339U-3+T&R shares the 8-TSSOP package footprint and I2C interface with MCP79401T-I/ST. Pin-to-pin compatibility must be verified against device datasheets, as TSSOP packages may have different pin assignments. Supply voltage range (2.7V ~ 5.5V) is compatible with systems operating above 2.7V. The part includes alarm and trickle-charger features not present in MCP79401T-I/ST.

Q: What is the key difference between 8-SOIC and 8-TSSOP packages for RTC substitution?

A: 8-SOIC (0.154", 3.90mm Width) and 8-TSSOP (0.173", 4.40mm Width) are distinct surface mount packages with different footprints and PCB land patterns. Direct substitution requires PCB redesign. 8-SOIC packages are more widely available in the substitute list. 8-TSSOP packages are limited to DS1339U series and DS1341T+T&R variants.

Q: Which substitute part has the lowest timekeeping current consumption?

A: DS1341T+T&R specifies 0.5µA ~ 0.6µA timekeeping current at 3V ~ 5V, which is lower than MCP79401T-I/ST at 1.2µA typical @ 3.3V. DS1337S+ specifies 0.6µA @ 1.3V ~ 1.8V. These parts are suitable for ultra-low-power battery-backed applications.

Q: Are all substitute parts RoHS3 compliant?

A: All listed substitute parts are ROHS3 compliant with MSL Level 1 (Unlimited moisture sensitivity), matching the environmental compliance profile of MCP79401T-I/ST.

Q: What supply voltage range is common across all substitute parts?

A: No single voltage range spans all substitutes. The overlapping range across most parts is 2.7V ~ 5.5V. For applications requiring 1.8V minimum supply, only MCP79401T-I/ST, DS1337S+, and DS1341T+T&R are suitable. For 3.3V fixed supply systems, all parts except BQ32002DR (3V ~ 3.6V) are compatible.

Q: Can BQ32002DR replace MCP79401T-I/ST in a 5V system?

A: No. BQ32002DR operates only at 3V ~ 3.6V supply range and cannot function in 5V systems. Additionally, BQ32002DR supports 24-hour time format only, whereas MCP79401T-I/ST supports both 12/24-hour formats.

Q: Which substitute parts include trickle-charger functionality?

A: DS1339U-3+T&R, DS1339U-33+, and DS1340Z-33+ include trickle-charger features for battery charging applications. MCP79401T-I/ST does not specify trickle-charger capability.

Q: Is memory size a critical factor in RTC substitution?

A: Memory size varies across substitutes (56B to 64B SRAM/NVSRAM). MCP79401T-I/ST provides 64B with unique ID feature. Substitutes with 56B memory are functionally compatible for standard timekeeping applications. NVSRAM variants (DS1307, DS1338, 1338-31DCGI) retain data during power loss, whereas standard SRAM does not.

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