BU9873FVT-GE2 Equivalent & Substitute Parts

Part Overview

The BU9873FVT-GE2 is a Real Time Clock (RTC) IC with Clock/Calendar functionality manufactured by Rohm Semiconductor. It features I2C/2-Wire Serial interface, alarm capability, and leap year support with a supply voltage range of 1.8V to 5.5V. The device is packaged in 8-TSSOP (0.173", 4.40mm Width) and carries a product status of Not For New Designs. Due to this obsolescence status and limited design flexibility, equivalent substitute parts with active product status are necessary for new applications and long-term availability assurance.

Key Parameters

Parameter	BU9873FVT-GE2
Manufacturer	Rohm Semiconductor
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Features	Alarm, Leap Year
Voltage - Supply	1.8V ~ 5.5V
Current - Timekeeping (Max)	1µA ~ 1.35µA @ 3V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package / Case	8-TSSOP (0.173", 4.40mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Product Status	Not For New Designs

Substitute Part Grouping Explanation

Substitution eligibility is determined by the following critical parameters:

Interface Compatibility: All substitute parts must support I2C/2-Wire Serial protocol to ensure software and hardware compatibility.

Functional Features: Alarm and Leap Year support are mandatory features present in the BU9873FVT-GE2. Substitute parts must include these capabilities.

Time and Date Format: All substitutes must support HH:MM:SS (12/24 hr) time format and YY-MM-DD-dd date format.

Supply Voltage Range: The BU9873FVT-GE2 operates from 1.8V to 5.5V. Substitute parts must have overlapping or compatible voltage ranges to function in the same power supply environment.

Operating Temperature: All substitutes must maintain -40°C to 85°C operating temperature range for thermal compatibility.

Compliance: RoHS3 compliance and REACH unaffected status are required for regulatory alignment.

Package Consideration: While the original part uses 8-TSSOP packaging, substitute parts may use alternative 8-pin or larger packages (8-SOIC, 16-SOIC, 10-SMD Module) provided PCB layout can accommodate the different footprint dimensions.

Parameter Comparison

Part Number	Manufacturer	Interface	Time Format	Date Format	Features	Voltage Supply	Timekeeping Current (Max)	Operating Temp	Package	Product Status
BU9873FVT-GE2	Rohm Semiconductor	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Alarm, Leap Year	1.8V ~ 5.5V	1µA ~ 1.35µA @ 3V ~ 5.5V	-40°C ~ 85°C	8-TSSOP	Not For New Designs
1338-31DCGI8	Renesas Electronics	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Leap Year, NVSRAM, Square Wave Output	3.3V ~ 5.5V	5µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
1339-31DCGI	Renesas Electronics	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave Output, Trickle-Charger	3.3V ~ 5.5V	200µA @ 3.63V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
AB-RTCMC-32.768KHZ-B5ZE-S3-T	Abracon LLC	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave Output	1.2V ~ 5.5V	0.5µA @ 2V ~ 5V	-40°C ~ 85°C	10-SMD Module	Active
DS1339C-33#T&R	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave Output, Trickle-Charger	2.97V ~ 5.5V	200µA @ 5.5V	-40°C ~ 85°C	16-SOIC	Active
DS1340Z-18+	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	HH:MM:SS (24 hr)	YY-MM-DD-dd	Leap Year, Trickle-Charger	1.71V ~ 5.5V	100µA @ 1.89V	-40°C ~ 85°C	8-SOIC	Active
DS1388Z-33+T&R	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	HH:MM:SS:hh (12/24 hr)	YY-MM-DD-dd	EEPROM, Leap Year, Supervisor, Trickle-Charger, Watchdog Timer	2.97V ~ 3.63V	150µA @ 2.97V ~ 3.63V	-40°C ~ 85°C	8-SOIC	Active
DS3232MZ+	Analog Devices Inc./Maxim Integrated	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Alarm, Leap Year, Square Wave Output, SRAM	2.3V ~ 4.5V	175µA @ 2.3V ~ 4.5V	-40°C ~ 85°C	8-SOIC	Active
ISL12058IBZ	Renesas Electronics	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Alarm, Leap Year	1.8V ~ 3.6V	0.65µA @ 1.8V	-40°C ~ 85°C	8-SOIC	Active
M41T11M6F	STMicroelectronics	I2C, 2-Wire Serial	HH:MM:SS (12/24 hr)	YY-MM-DD-dd	Leap Year, NVSRAM	2V ~ 5.5V	70µA @ 2V ~ 5.5V	-40°C ~ 85°C	8-SOIC	Active
M41T82SM6F	STMicroelectronics	I2C, 2-Wire Serial	HH:MM:SS:hh (24 hr)	YY-MM-DD-dd	Alarm, Leap Year, SRAM, Watchdog Timer	3V ~ 5.5V	10µA @ 5.5V	-40°C ~ 85°C	8-SOIC	Active

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility):

1339-31DCGI and 1338-31DCGI8 (Renesas Electronics) are the most direct substitutes. Both maintain I2C interface, alarm functionality, leap year support, and 12/24-hour time format. The 1339-31DCGI includes trickle-charger capability and is in active product status. The 1338-31DCGI8 adds NVSRAM and square wave output. Both use 8-SOIC packaging requiring PCB layout adjustment from the original 8-TSSOP.

ISL12058IBZ (Renesas Electronics) provides excellent low-power performance at 0.65µA timekeeping current and maintains the full feature set of alarm and leap year support. Supply voltage range is 1.8V to 3.6V, which is narrower than the original but covers the critical 1.8V lower bound. Active product status ensures long-term availability.

Alternative Substitutes (Feature-Enhanced):

DS1339C-33#T&R and DS1340Z-18+ (Analog Devices/Maxim Integrated) are active products with full I2C compatibility and leap year support. DS1339C-33#T&R includes alarm functionality and operates from 2.97V to 5.5V. DS1340Z-18+ supports 24-hour format only and operates from 1.71V to 5.5V, providing the widest low-voltage coverage. Both use 8-SOIC packaging.

DS3232MZ+ (Analog Devices/Maxim Integrated) includes integrated SRAM and alarm capability but operates within a narrower voltage range (2.3V to 4.5V). This part is suitable only for applications with fixed 3.3V or 5V supplies.

M41T82SM6F (STMicroelectronics) offers the lowest timekeeping current at 10µA and includes watchdog timer functionality. It supports 24-hour format only and requires 3V minimum supply voltage.

AB-RTCMC-32.768KHZ-B5ZE-S3-T (Abracon LLC) is a module-level solution with the lowest timekeeping current (0.5µA) and widest supply range (1.2V to 5.5V). The 10-SMD Module package requires significant PCB layout redesign but provides integrated oscillator and battery backup.

Voltage Range Considerations:

Applications requiring the full 1.8V to 5.5V range of the BU9873FVT-GE2 should prioritize ISL12058IBZ (1.8V to 3.6V), DS1340Z-18+ (1.71V to 5.5V), or AB-RTCMC-32.768KHZ-B5ZE-S3-T (1.2V to 5.5V). Applications with fixed 3.3V or 5V supplies have broader options across all listed substitutes.

All substitute parts maintain RoHS3 compliance and REACH unaffected status, ensuring regulatory alignment with the original BU9873FVT-GE2.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part with a different package type?

A: Yes, provided your PCB layout can accommodate the different footprint. The BU9873FVT-GE2 uses 8-TSSOP (0.173", 4.40mm width). Most substitutes use 8-SOIC (0.154", 3.90mm width), which is slightly narrower. The AB-RTCMC module uses a 10-SMD package requiring more significant redesign. Verify pin-to-pin compatibility and signal routing before layout changes.

Q: Which substitute has the lowest power consumption?

A: AB-RTCMC-32.768KHZ-B5ZE-S3-T offers the lowest timekeeping current at 0.5µA @ 2V to 5V. ISL12058IBZ provides 0.65µA @ 1.8V, and M41T82SM6F delivers 10µA @ 5.5V. Selection depends on your specific supply voltage and power budget requirements.

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

A: Most substitutes support both 12/24-hour formats. DS1340Z-18+ and M41T82SM6F support 24-hour format only. Verify your firmware can operate with 24-hour format if selecting these parts.

Q: What is the minimum supply voltage I should use?

A: The BU9873FVT-GE2 operates from 1.8V minimum. Substitutes vary: ISL12058IBZ (1.8V), DS1340Z-18+ (1.71V), and AB-RTCMC (1.2V) support low voltages. DS1388Z-33+T&R requires 2.97V minimum. Verify your power supply design matches the selected substitute's minimum voltage specification.

Q: Are all substitutes RoHS3 compliant?

A: Yes, all listed substitute parts are RoHS3 compliant and REACH unaffected, matching the regulatory status of the BU9873FVT-GE2.

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

A: AB-RTCMC-32.768KHZ-B5ZE-S3-T supports battery backup from 1.8V to 5.5V with the lowest timekeeping current (0.5µA). ISL12058IBZ also supports battery operation with 0.65µA consumption. DS1339C-33#T&R and 1339-31DCGI include trickle-charger functionality for supercapacitor charging.

Q: Can I directly replace the BU9873FVT-GE2 without firmware changes?

A: I2C protocol compatibility is maintained across all substitutes, but verify register mapping and command sequences in the datasheet of your selected substitute. Time and date format support (12/24-hour, YY-MM-DD-dd) is consistent across all options, minimizing firmware modifications.

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