Renesas ISL12028IB27Z

Overview

ISL12028IB27Z from Intersil is a low-power real-time clock/calendar IC with integrated 512×8-bit EEPROM, I²C interface, dual non-volatile alarms, CPU supervisor (POR, watchdog timer, low-voltage reset), and automatic battery backup switching. It operates from 2.7V to 5.5V main supply and retains timekeeping down to 1.8V on VBAT, features ±30ppm digital crystal compensation, and delivers 1Hz/4.096kHz/32.768kHz selectable frequency output via IRQ/FOUT pin - used in utility meters and industrial control systems requiring long-term time accuracy and data retention.

For engineers reviewing the ISL12028IB27Z datasheet, ISL12028IB27Z pinout, ISL12028IB27Z application, or ISL12028IB27Z equivalent, key selection criteria include VBAT trip point (2.63V), legacy power-control mode (BSW=1), SOIC-14 package compatibility, 400kHz I²C timing compliance, and EEPROM endurance (>2M cycles) for firmware configuration storage in field-deployed equipment.

Technical Context

The ISL12028IB27Z implements a fully autonomous RTC subsystem with separate volatile timekeeping registers (BCD-coded seconds, minutes, hours, date, month, year, day-of-week) and non-volatile alarm registers supporting repeat-mode interrupts. Its oscillator uses an external 32.768kHz crystal with on-chip 64-position digitally controlled trim capacitor and six discrete frequency adjustment settings for ±30ppm calibration across temperature.

CPU supervision includes three programmable watchdog timeout periods (225ms/750ms/1.75s), five selectable VRESET thresholds (2.63V/3.09V/4.38V/4.64V), and power-on reset with 100–400ms delay. The device supports I²C communication during battery backup only when explicitly enabled via register control - default behavior disables I²C in VBAT mode.

Key Specifications

Pinout & Package

ISL12028IB27Z is housed in a Pb-free, RoHS-compliant 14-lead SOIC package (JEDEC MS-012, package drawing M14.15), with 1.27mm lead pitch and 8.65mm × 3.9mm body dimensions. Thermal resistance θ_JA = 90°C/W enables stable operation under continuous 10µA timekeeping current.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock/calendar applications.

Compared with DS3231SN#T&R and PCF8563T, the ISL12028IB27Z uniquely balances integrated supervision, field-trimmable accuracy, and robust EEPROM in a single SOIC package - making it optimal for industrial metering and infrastructure equipment needing long-term reliability without external timing components.

Availability

ISL12028IB27Z is available at Aetrix Electronics and suitable for utility metering, HVAC control, and network infrastructure applications requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.

Supply support for ISL12028IB27Z includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Intersil (now part of Renesas Electronics) is a semiconductor company specializing in precision analog, power management, and timing solutions for industrial, communications, and computing markets.

The ISL12028 product line was designed for embedded systems requiring autonomous, battery-backed timekeeping with integrated supervision and non-volatile memory - targeting metering, infrastructure, and industrial control applications demanding high reliability and field configurability.

FAQ

What is the VBAT trip voltage setting for ISL12028IB27Z?

The ISL12028IB27Z has a fixed VBAT trip voltage of 2.63V, as specified in the Ordering Information table. This threshold triggers automatic switchover from VDD to VBAT supply when main power drops below this level. The device also incorporates 50mV hysteresis to prevent chattering during marginal supply conditions. This value is factory-programmed and cannot be modified in-circuit.

Does ISL12028IB27Z support I²C communication during battery backup mode?

Yes, ISL12028IB27Z supports I²C communication during battery backup, but only when explicitly enabled via the I²CEN bit in the control register. By default, the I²C interface is disabled in VBAT mode to minimize current draw. Enabling it allows host processors to read RTC registers or update alarms while running on backup power - critical for uninterrupted logging in utility meters.

How many EEPROM write cycles does ISL12028IB27Z guarantee?

The ISL12028IB27Z guarantees >2,000,000 write cycles per byte across its 512×8-bit EEPROM array. This endurance rating applies under standard operating conditions (TA = –40°C to +85°C, VDD = 2.7V–5.5V) and enables reliable storage of calibration data, firmware flags, and event counters in field-deployed equipment with infrequent but mission-critical writes.

What crystal specifications are required for ISL12028IB27Z?

ISL12028IB27Z requires a standard 32.768kHz tuning-fork quartz crystal with load capacitance of 12.5pF. No external capacitors or resistors are needed - all compensation components are integrated. The device's 64-position digital trim capacitor and six frequency offset settings allow fine-tuning to achieve ±30ppm accuracy across temperature, eliminating manual calibration labor.

Can ISL12028IB27Z generate multiple frequency outputs?

Yes, ISL12028IB27Z can generate three selectable frequency outputs - 1Hz, 4.096kHz, or 32.768kHz - on the IRQ/FOUT pin. The output mode is configured via software-controlled bits in the control/status register. All outputs are CMOS push-pull, requiring no external pull-up resistor, and maintain low jitter suitable for driving downstream logic or microcontroller clock inputs.