ISL12028IB27Z Real Time Clock (RTC) IC Equivalent & Substitute Parts

Part Overview

The ISL12028IB27Z is a Real Time Clock (RTC) IC manufactured by Renesas Electronics Corporation, designed for Clock/Calendar applications with I2C, 2-Wire Serial interface. This device provides timekeeping functionality with alarm, leap year compensation, supervisor, and watchdog timer features in a 14-SOIC surface mount package.

The ISL12028IB27Z is classified as Obsolete. Due to its discontinued status, identifying functionally equivalent substitute parts is essential for system redesign, production continuation, and long-term component availability assurance. Substitute parts must maintain compatibility across critical electrical parameters, interface protocols, and mechanical form factors.

Key Parameters

Parameter	ISL12028IB27Z
Manufacturer	Renesas Electronics Corporation
Category	Clock/Timing
Type	Clock/Calendar
Interface	I2C, 2-Wire Serial
Package / Case	14-SOIC (0.154", 3.90mm Width)
Voltage - Supply	2.7V ~ 5.5V
Voltage - Supply, Battery	1.8V ~ 5.5V
Current - Timekeeping (Max)	10µA ~ 20µA @ 2.7V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Features	Alarm, Leap Year, Supervisor, Watchdog Timer
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitute parts for the ISL12028IB27Z are evaluated based on the following critical parameters that determine functional compatibility:

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

Voltage Supply Range: Substitute parts must operate within or encompass the ISL12028IB27Z supply voltage range of 2.7V ~ 5.5V for main supply and 1.8V ~ 5.5V for battery supply to maintain system power compatibility.

Time and Date Format: All substitutes must support HH:MM:SS (12/24 hr) time format and YY-MM-DD-dd date format to ensure firmware compatibility without modification.

Operating Temperature Range: Substitute parts must support the full -40°C ~ 85°C operating temperature range to maintain performance across all environmental conditions.

Package Mechanical Compatibility: While the ISL12028IB27Z uses a 14-SOIC package, substitute parts may use alternative SOIC, TSSOP, or module packages provided the pin count, pitch, and electrical interface remain compatible with the application PCB layout.

Feature Set: Core features including Alarm, Leap Year compensation, and timekeeping functionality must be present. Additional features such as SRAM, Square Wave Output, or Watchdog Timer enhance functionality but are not mandatory for substitution.

Compliance Standards: All substitute parts must maintain ROHS3 compliance and EAR99 export classification to meet regulatory and supply chain requirements.

Parameter Comparison

Parameter	ISL12028IB27Z	AB-RTCMC-32.768KHZ-B5ZE-S3-T	DS1338U-18+T&R	DS1338Z-18+	DS1338Z-33+	DS1340C-33#	DS3231MZ+TRL	DS3232MZ+	M41T83SMY6F	MCP79400T-I/SN	MCP79401T-I/MS
Manufacturer	Renesas	Abracon LLC	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	Analog Devices/Maxim	STMicroelectronics	Microchip Technology	Microchip Technology
Interface	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire	I2C, 2-Wire
Voltage - Supply (V)	2.7 ~ 5.5	1.2 ~ 5.5	1.71 ~ 5.5	1.71 ~ 5.5	3.0 ~ 5.5	2.97 ~ 5.5	2.3 ~ 5.5	2.3 ~ 4.5	3.0 ~ 5.5	1.8 ~ 5.5	1.8 ~ 5.5
Voltage - Battery (V)	1.8 ~ 5.5	1.8 ~ 5.5	1.3 ~ 3.7	1.3 ~ 3.7	1.3 ~ 3.7	1.3 ~ 5.5	2.3 ~ 5.5	2.3 ~ 4.5	2.0 ~ 5.5	1.3 ~ 5.5	1.3 ~ 5.5
Time Format	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS:hh (24 hr)	HH:MM:SS (12/24 hr)	HH:MM:SS (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	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd	YY-MM-DD-dd
Operating Temperature (°C)	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85	-40 ~ 85
Package / Case	14-SOIC (3.90mm)	10-SMD Module	8-TSSOP/MSOP (3.00mm)	8-SOIC (3.90mm)	8-SOIC (3.90mm)	16-SOIC (7.50mm)	8-SOIC (3.90mm)	8-SOIC (3.90mm)	18-SOX (7.5mm)	8-SOIC (3.90mm)	8-TSSOP/MSOP (3.00mm)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active	Active	Active

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility):

DS1338Z-18+ and DS1338Z-33+ from Analog Devices Inc./Maxim Integrated are the most direct substitutes. Both maintain I2C interface, support 12/24-hour time format with YY-MM-DD-dd date format, and operate across the -40°C ~ 85°C temperature range. The DS1338Z-18+ supports supply voltage from 1.71V ~ 5.5V, encompassing the ISL12028IB27Z range. Both are Active products with ROHS3 compliance and unlimited MSL rating, ensuring long-term availability and supply chain stability.

Secondary Substitutes (Package Consideration):

MCP79400T-I/SN and MCP79401T-I/MS from Microchip Technology provide extended supply voltage compatibility (1.8V ~ 5.5V main supply) and superior low-power timekeeping performance (1.2µA typical @ 3.3V). These parts include 64B SRAM and Unique ID features. MCP79400T-I/SN uses 8-SOIC packaging matching the ISL12028IB27Z footprint width (3.90mm), while MCP79401T-I/MS uses 8-TSSOP/MSOP (3.00mm width) requiring PCB layout modification.

Alternative Substitutes (Feature Enhancement):

DS3231MZ+TRL and DS3232MZ+ offer enhanced timekeeping accuracy and additional features. DS3231MZ+TRL includes integrated temperature-compensated crystal oscillator (TCXO) with alarm and square wave output. DS3232MZ+ adds 236B SRAM for extended data storage. Both maintain I2C interface and -40°C ~ 85°C operation but require firmware evaluation for feature utilization.

Module-Based Substitute:

AB-RTCMC-32.768KHZ-B5ZE-S3-T from Abracon LLC provides an integrated RTC module with 32.768 kHz crystal, reducing external component count. This 10-SMD module format requires different PCB integration approach but offers superior power efficiency (0.5µA @ 2V ~ 5V timekeeping current).

Voltage Supply Constraint:

DS1338Z-33+ and DS1340C-33# specify minimum supply voltage of 3.0V and 2.97V respectively, restricting use in systems requiring operation below 3.0V. These parts are suitable only for applications with 3.0V minimum supply voltage.

All recommended substitutes maintain ROHS3 compliance, EAR99 export classification, and Active product status, ensuring regulatory compliance and supply chain continuity.

Frequently Asked Questions (FAQ)

Q: Can DS1338Z-33+ directly replace ISL12028IB27Z in all applications?

A: DS1338Z-33+ is functionally compatible for I2C interface, time/date format, and operating temperature range. However, it specifies minimum supply voltage of 3.0V, while ISL12028IB27Z operates from 2.7V. Use DS1338Z-33+ only in systems with 3.0V or higher supply voltage. For systems requiring 2.7V operation, use DS1338Z-18+ instead.

Q: What is the primary difference between MCP79400T-I/SN and MCP79401T-I/MS?

A: Both parts are functionally identical with identical electrical specifications and feature sets. The primary difference is packaging: MCP79400T-I/SN uses 8-SOIC (0.154", 3.90mm width) matching ISL12028IB27Z footprint width, while MCP79401T-I/MS uses 8-TSSOP/MSOP (0.118", 3.00mm width) requiring PCB layout modification. Select based on available PCB footprint.

Q: Does DS1340C-33# support 12-hour time format like ISL12028IB27Z?

A: No. DS1340C-33# supports only 24-hour time format, while ISL12028IB27Z supports both 12-hour and 24-hour formats. If firmware requires 12-hour format capability, use DS1338Z-18+, DS1338Z-33+, DS3231MZ+TRL, DS3232MZ+, MCP79400T-I/SN, or MCP79401T-I/MS instead.

Q: What is the advantage of DS3231MZ+TRL over DS1338Z-18+?

A: DS3231MZ+TRL integrates a temperature-compensated crystal oscillator (TCXO), providing superior timekeeping accuracy without external crystal component. This reduces BOM complexity and improves frequency stability across temperature variations. DS1338Z-18+ requires external 32.768 kHz crystal. Select DS3231MZ+TRL for applications requiring high accuracy timekeeping; select DS1338Z-18+ for cost-optimized designs.

Q: Can AB-RTCMC-32.768KHZ-B5ZE-S3-T module replace ISL12028IB27Z?

A: AB-RTCMC-32.768KHZ-B5ZE-S3-T is functionally compatible for I2C interface and timekeeping operation. However, it uses 10-SMD module packaging instead of 14-SOIC DIP package, requiring different PCB integration approach and footprint design. This module is suitable for new designs but not for direct PCB replacement of ISL12028IB27Z.

Q: Which substitute offers the lowest power consumption during timekeeping?

A: AB-RTCMC-32.768KHZ-B5ZE-S3-T offers the lowest timekeeping current at 0.5µA @ 2V ~ 5V. MCP79400T-I/SN and MCP79401T-I/MS provide 1.2µA typical @ 3.3V. ISL12028IB27Z specifies 10µA ~ 20µA, making the Abracon module and Microchip parts significantly more power-efficient for battery-backed applications.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts maintain ROHS3 compliance and EAR99 export classification, matching ISL12028IB27Z regulatory status. All parts are suitable for applications requiring environmental and export compliance.

Q: What is the MSL (Moisture Sensitivity Level) rating for substitute parts?

A: All substitute parts specify MSL 1 (Unlimited shelf life), compared to ISL12028IB27Z MSL 2 (1 Year). This indicates substitute parts have superior moisture resistance and longer shelf life without special storage requirements.

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