Renesas ISL12057IUZ-T

Overview

ISL12057IUZ-T from Renesas Electronics is a low-power I²C real-time clock/calendar IC with dual interrupt pins (IRQ1/FOUT and IRQ2), two programmable alarms, and four selectable frequency outputs (1Hz, 4096Hz, 8192Hz, 32.768kHz). It operates from 1.4V to 3.6V, consumes as low as 400nA in timekeeping mode, and maintains calendar accuracy through 2099 with automatic leap-year correction. It is used in utility meters, HVAC controllers, and network infrastructure equipment for precise timestamping and alarm-triggered event management.

For engineers reviewing the ISL12057IUZ-T datasheet, ISL12057IUZ-T pinout, ISL12057IUZ-T application, or ISL12057IUZ-T equivalent, this page delivers verified technical context, exact pin functions, confirmed I²C timing compliance (400kHz), validated alarm granularity (down to second-level match), and manufacturer-confirmed functional equivalence to Maxim DS1337 - all critical for RTC selection in battery-backed industrial and consumer systems.

Technical Context

The ISL12057IUZ-T implements a crystal-based RTC core using an external 32.768kHz oscillator with 6pF load capacitance, supporting BCD-encoded timekeeping registers (seconds, minutes, hours, day-of-week, date, month, year) and automatic century-bit toggle at year rollover. Its dual-alarm architecture allows independent configuration of Alarm1 (match down to seconds) and Alarm2 (match down to minutes), each with dedicated status flags (A1F/A2F) and interrupt routing via open-drain IRQ1/FOUT or IRQ2 pins.

Interrupt behavior is controlled by the INTCN bit and A1IE/A2IE enable bits in register 0Eh, enabling flexible routing: IRQ1/FOUT can serve as frequency output (32.768kHz/8192Hz/4096Hz/1Hz) or Alarm1/Alarm2 interrupt, while IRQ2 supports Alarm1 or Alarm2 assertion. The device defaults to 32.768kHz FOUT at power-up and enters low-power oscillator disable mode when EOSC=1.

Key Specifications

Pinout & Package

ISL12057IUZ-T is housed in an 8-lead MSOP package (M8.118, 3.0mm × 3.0mm × 1.0mm height, RoHS-compliant matte tin finish), optimized for space-constrained industrial PCBs and compatible with reflow profiles per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1337+T&R and PCF8563T/5,118, the ISL12057IUZ-T uniquely combines sub-1µA timekeeping current, dual configurable alarms, four frequency outputs, and guaranteed 1.4V operation - making it optimal for battery-critical, feature-rich industrial RTC deployments.

Availability

ISL12057IUZ-T is available at Aetrix Electronics and suitable for utility metering, HVAC control systems, and network infrastructure equipment requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for ISL12057IUZ-T 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

Renesas Electronics is a global semiconductor leader specializing in microcontrollers, analog, power, and timing solutions for industrial, automotive, and infrastructure markets.

The ISL12057 series was designed as a low-power, pin-compatible upgrade to legacy RTCs like the DS1337, targeting cost-sensitive, battery-backed applications demanding high calendar accuracy and flexible alarm architecture.

FAQ

What is the minimum VDD voltage that maintains timekeeping functionality in the ISL12057IUZ-T?

The ISL12057IUZ-T retains timekeeping functionality down to 1.4V, as specified in the DC Operating Characteristics table (VDDT = 1.4V min). Below 1.4V, the RTC stops incrementing; at 1.4V–1.8V, it operates in reduced-functionality timekeeping mode with typical current draw of 350–400nA. This enables multi-year operation from a single CR2032 coin cell.

How does the ISL12057IUZ-T handle leap years, and does it support year 2100?

The ISL12057IUZ-T implements full Gregorian calendar rules: years divisible by 4 are leap years, except years divisible by 100 unless also divisible by 400. Thus, 2000 is correctly treated as a leap year, while 2100 is correctly excluded. The device maintains calendar accuracy through 2099, and the MO register's century bit (bit 7) toggles at year 00 rollover to signal century transition.

Can the ISL12057IUZ-T generate a 1Hz output synchronized to the RTC second boundary?

Yes. When RS2=0 and RS1=0 in the Interrupt Control Register (0Eh), the ISL12057IUZ-T configures IRQ1/FOUT for 1Hz output synchronized to the RTC's internal second counter - meaning the rising edge occurs precisely at the start of each new second (e.g., 12:00:00.000), eliminating jitter or phase drift common in divider-based outputs.

Is the ISL12057IUZ-T pin-compatible with the Maxim DS1337, and what does that mean for PCB layout?

Yes - the ISL12057IUZ-T is fully pin-compatible and functionally equivalent to the Maxim DS1337 in both 8-lead SOIC and 8-lead MSOP packages. Pin assignments, register map, I²C slave address (0x68), and timing specifications match exactly. No PCB layout changes, footprint modifications, or schematic updates are required for drop-in replacement.

What is the maximum capacitive load the ISL12057IUZ-T SDA and SCL pins can drive while maintaining 400kHz I²C compliance?

The ISL12057IUZ-T specifies a maximum total bus capacitance (Cb) of 400pF for guaranteed 400kHz I²C operation, per the tR/tF timing parameters. With 400pF loading, the recommended external pull-up resistor is ~2kΩ to ~2.5kΩ. Exceeding 400pF may violate rise/fall time specs (tR/tF ≤300ns), risking communication errors at maximum speed.