ISL12028IBAZ Real Time Clock (RTC) IC Equivalent & Substitute Parts

Part Overview

The ISL12028IBAZ is a Real Time Clock (RTC) IC manufactured by Renesas Electronics Corporation, designed for clock/calendar applications with I2C 2-Wire Serial interface in a 14-SOIC package. This device provides timekeeping functionality with alarm, leap year, supervisor, and watchdog timer features across a 2.7V to 5.5V supply voltage range.

The ISL12028IBAZ is classified as Obsolete. Identifying equivalent and substitute parts is necessary to ensure design continuity, maintain supply chain reliability, and support long-term product availability for applications requiring RTC functionality with comparable electrical and mechanical specifications.

Key Parameters

Parameter	ISL12028IBAZ
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 ISL12028IBAZ are selected based on the following critical parameters that determine functional and mechanical compatibility:

Primary Substitution Criteria:

Interface: I2C, 2-Wire Serial (mandatory match)
Time Format: HH:MM:SS with 12/24 hour capability
Date Format: YY-MM-DD-dd
Operating Temperature: -40°C ~ 85°C
Voltage - Supply: Overlapping range with 2.7V ~ 5.5V
Voltage - Supply, Battery: Support for 1.8V ~ 5.5V range
Mounting Type: Surface Mount
RoHS Status: ROHS3 Compliant

Secondary Considerations:

Package form factor (SOIC, TSSOP, Module variants acceptable)
Feature set (Alarm, Leap Year as baseline requirements)
Product Status (Active preferred for new designs; Not For New Designs acceptable for legacy support)

Substitute parts are grouped into two categories: direct pin-compatible alternatives and functional equivalents with different package configurations. All listed substitutes maintain I2C interface compatibility and support the required voltage and temperature ranges.

Parameter Comparison

Parameter	ISL12028IBAZ	AB-RTCMC-32.768KHZ-B5ZE-S3-T	AB-RTCMC-32.768KHZ-EOZ9-S3-DBT	BQ32002D	BU9873F-GTE2	DS1308U-3+T	DS1337S+T&R	DS1338C-18#	DS1338U-18+	DS1339U-33+T&R	DS1340C-3#
Manufacturer	Renesas	Abracon LLC	Abracon LLC	Texas Instruments	Rohm Semiconductor	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim	Analog Devices Inc./Maxim
Interface	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial	I2C, 2-Wire Serial
Time Format	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 (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)
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
Voltage - Supply	2.7V ~ 5.5V	1.2V ~ 5.5V	1.4V ~ 5.5V	3V ~ 3.6V	1.8V ~ 5.5V	2.7V ~ 5.5V	1.8V ~ 5.5V	1.71V ~ 5.5V	1.71V ~ 5.5V	2.97V ~ 5.5V	2.7V ~ 5.5V
Voltage - Supply, Battery	1.8V ~ 5.5V	1.8V ~ 5.5V	1.4V ~ 5.5V	1.4V ~ 3.6V	Not specified	1.3V ~ 5.5V	Not specified	1.3V ~ 3.7V	1.3V ~ 3.7V	1.3V ~ 3.7V	1.3V ~ 3.7V
Operating Temperature	-40°C ~ 85°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	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	14-SOIC (0.154", 3.90mm)	10-SMD Module	10-SMD Module	8-SOIC (0.154", 3.90mm)	8-SOIC (0.173", 4.40mm)	8-TSSOP, 8-MSOP (0.118", 3.00mm)	8-SOIC (0.154", 3.90mm)	16-SOIC (0.295", 7.50mm)	8-TSSOP, 8-MSOP (0.118", 3.00mm)	8-TSSOP, 8-MSOP (0.118", 3.00mm)	16-SOIC (0.295", 7.50mm)
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	Not For New Designs	Active	Active	Active	Active	Active	Active

Engineering Selection Recommendations

Primary Substitutes (Active Status, Full Compatibility):

DS1337S+T&R and DS1338C-18# are recommended as primary substitutes. Both are manufactured by Analog Devices Inc./Maxim Integrated with Active product status, ensuring long-term availability and support. DS1337S+T&R provides an 8-SOIC package matching the ISL12028IBAZ footprint width (0.154", 3.90mm), while DS1338C-18# offers expanded functionality with 56B NVSRAM in a 16-SOIC package. Both support I2C interface, 12/24-hour time format, YY-MM-DD-dd date format, and -40°C to 85°C operating temperature range. Voltage supply ranges (1.8V ~ 5.5V for DS1337S+T&R; 1.71V ~ 5.5V for DS1338C-18#) encompass the ISL12028IBAZ specification.

Secondary Substitutes (Active Status, Module Form Factor):

AB-RTCMC-32.768KHZ-B5ZE-S3-T and AB-RTCMC-32.768KHZ-EOZ9-S3-DBT are manufactured by Abracon LLC with Active product status. These integrated RTC modules provide complete clock/calendar functionality in 10-SMD Module packages. The EOZ9 variant includes 8B EEPROM, SRAM, TCXO/Crystal, and trickle-charger features. Both support I2C interface and -40°C to 85°C operation. The B5ZE variant operates at 1.2V ~ 5.5V supply with 0.5µA timekeeping current, while the EOZ9 variant operates at 1.4V ~ 5.5V with 1.5µA ~ 2.2µA timekeeping current. These modules are suitable for applications where integrated solutions reduce component count.

Tertiary Substitutes (Active Status, Specialized Applications):

DS1339U-33+T&R and DS1340C-3# offer additional features for specific applications. DS1339U-33+T&R includes trickle-charger functionality in an 8-TSSOP package with 2.97V ~ 5.5V supply range. DS1340C-3# provides 24-hour time format in a 16-SOIC package with trickle-charger support and 2.7V ~ 5.5V supply range. Both maintain I2C compatibility and -40°C to 85°C operation.

Legacy Support (Not For New Designs):

BU9873F-GTE2 is classified as Not For New Designs but remains available with 1401 pcs inventory. This Rohm Semiconductor device supports I2C interface, 12/24-hour time format, and 1.8V ~ 5.5V supply range in an 8-SOIC package. Use only for legacy system maintenance or replacement scenarios.

Voltage-Constrained Applications:

BQ32002D from Texas Instruments operates within a narrower supply range (3V ~ 3.6V) and supports 24-hour time format only. This device is suitable only for applications with fixed 3.3V supply and no 12-hour format requirement.

All recommended substitutes maintain ROHS3 compliance and support the required -40°C to 85°C operating temperature range.

Frequently Asked Questions (FAQ)

Q: Can DS1337S+T&R directly replace ISL12028IBAZ in existing PCB layouts?

A: DS1337S+T&R shares the same 8-SOIC (0.154", 3.90mm Width) package footprint as ISL12028IBAZ. However, the ISL12028IBAZ is a 14-pin device while DS1337S+T&R is 8-pin. PCB layout modification is required. Pin-to-pin compatibility must be verified against device datasheets before implementation.

Q: What is the key difference between AB-RTCMC-32.768KHZ-B5ZE-S3-T and AB-RTCMC-32.768KHZ-EOZ9-S3-DBT?

A: Both are Abracon LLC integrated RTC modules with I2C interface and -40°C to 85°C operation. The B5ZE variant provides basic clock/calendar functionality with 0.5µA timekeeping current at 1.2V ~ 5.5V supply. The EOZ9 variant includes 8B EEPROM, SRAM, TCXO/Crystal, and trickle-charger with 1.5µA ~ 2.2µA timekeeping current at 1.4V ~ 5.5V supply. Select B5ZE for minimal power consumption; select EOZ9 for applications requiring onboard memory and crystal oscillator.

Q: Why is BQ32002D not recommended as a primary substitute?

A: BQ32002D operates within a narrower supply voltage range (3V ~ 3.6V) compared to ISL12028IBAZ (2.7V ~ 5.5V). Additionally, BQ32002D supports 24-hour time format only, while ISL12028IBAZ supports both 12/24-hour formats. Use BQ32002D only in applications with fixed 3.3V supply and no 12-hour format requirement.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts are RoHS3 compliant, matching the ISL12028IBAZ compliance status. All devices are suitable for applications requiring RoHS3 certification.

Q: What is the significance of Product Status (Active vs. Obsolete vs. Not For New Designs)?

A: Product Status indicates manufacturer support and availability. Active status ensures long-term supply, technical support, and design continuity. Obsolete status indicates discontinued manufacturing; substitution is necessary for new designs. Not For New Designs indicates limited support; use only for legacy system maintenance. For new designs, prioritize Active status substitutes.

Q: Can I use DS1338C-18# or DS1338U-18+ if my application requires 56B NVSRAM?

A: Yes. Both DS1338C-18# and DS1338U-18+ include 56B NVSRAM, providing non-volatile storage beyond basic timekeeping. DS1338C-18# uses 16-SOIC package; DS1338U-18+ uses 8-TSSOP/8-MSOP package. Both support I2C interface, 12/24-hour time format, and -40°C to 85°C operation. Select based on PCB layout constraints and package availability.

Q: What is the timekeeping current difference between substitutes, and why does it matter?

A: Timekeeping current determines battery backup power consumption. ISL12028IBAZ draws 10µA ~ 20µA. AB-RTCMC-32.768KHZ-B5ZE-S3-T draws 0.5µA (lowest), while BQ32002D draws 200µA (highest). Lower timekeeping current extends battery life during power loss. Select based on backup battery capacity and required backup duration.

Q: Are module-based substitutes (Abracon) compatible with discrete IC designs?

A: Abracon RTC modules (AB-RTCMC series) integrate clock/calendar, crystal oscillator, and supporting components into a single module. These are compatible with I2C-based designs but require different PCB footprints and layout considerations compared to discrete ICs. Module-based solutions reduce component count and design complexity but may increase unit cost. Evaluate based on design requirements and cost constraints.

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