Renesas X1288S16I-4.5AT1

Overview

X1288S16I-4.5AT1 from Intersil is a 16-pin SOIC real-time clock/calendar with integrated 32K × 8 EEPROM, CPU supervisor (power-on reset, low-voltage sense, watchdog timer), and oscillator compensation circuitry. It operates from -40°C to +85°C, supports 400kHz I²C-compatible 2-wire interface, delivers 1.25µA timekeeping current at VBACK = 1.8V, and provides programmable frequency output (1Hz/100Hz/32.768kHz) or alarm interrupt on PHZ/IRQ.

For engineers reviewing the X1288S16I-4.5AT1 datasheet, X1288S16I-4.5AT1 pinout, X1288S16I-4.5AT1 application, or X1288S16I-4.5AT1 equivalent, key selection criteria include industrial-grade temperature range (-40°C to +85°C), nonvolatile dual alarms with repeat mode, on-chip oscillator trim (±30ppm digital adjustment), battery-switch architecture supporting VBACK down to 1.8V, and BlockLock™ EEPROM protection with 100-year data retention.

Technical Context

The X1288S16I-4.5AT1 integrates a 32.768kHz crystal oscillator with internal 64-position digitally controlled trim capacitor and six digital-frequency adjustment settings for ±30ppm accuracy tuning. Its RTC maintains time in hundredths of seconds, day-of-week, date, month, and year through 2099 with automatic leap-year correction.

It implements two nonvolatile polled alarms with match-enable bits per register field (second, minute, hour, day-of-week, date, month), configurable repeat modes, and status flag polling or active-low IRQ assertion. The CPU supervisor includes user-programmable VTRIP (4.63V ±112mV), selectable watchdog timeout (0.25s/0.75s/1.75s/off), and power-on reset with 250ms typical delay.

Key Specifications

Pinout & Package

Package: 16-lead SOIC (Small Outline Integrated Circuit), RoHS-compliant Pb-free plus anneal finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1339U-33+T&R and PCF8583P/03,118, the X1288S16I-4.5AT1 uniquely combines industrial temperature operation, on-chip oscillator trim, dual repeat-mode alarms, programmable VTRIP, and 32KB EEPROM - enabling single-chip timekeeping, supervision, and secure data logging without external components.

Availability

X1288S16I-4.5AT1 is available at Aetrix Electronics and suitable for utility metering, HVAC control, and network infrastructure applications requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for X1288S16I-4.5AT1 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 Corporation (now part of Renesas Electronics) is a U.S.-based semiconductor company specializing in precision analog, power management, and timing solutions for industrial, communications, and computing markets.

The X1288 product line was designed to integrate real-time clock, nonvolatile memory, and CPU supervision into a single IC for space-constrained, battery-backed systems requiring high reliability and long-term data integrity.

FAQ

What is the backup voltage range supported by the X1288S16I-4.5AT1?

The X1288S16I-4.5AT1 supports VBACK from 1.8V to 5.5V. At 1.8V, it draws only 1.25µA in timekeeping mode, enabling multi-year operation from common lithium coin cells or supercapacitors. The device automatically switches to VBACK when VCC falls below VBACK − 0.2V and reverts to VCC when VCC exceeds VBACK.

Does the X1288S16I-4.5AT1 require external load capacitors for the 32.768kHz crystal?

No, the X1288S16I-4.5AT1 integrates internal feedback resistor and compensation capacitors, including a 64-position digitally controlled trim capacitor. This eliminates external load capacitors and enables ±30ppm frequency adjustment via register writes - reducing BOM count and PCB area versus discrete oscillator solutions.

How does the X1288S16I-4.5AT1 handle leap years and calendar accuracy?

The X1288S16I-4.5AT1 implements full Gregorian calendar logic, automatically correcting for leap years (divisible by 4, excluding years divisible by 100 unless also divisible by 400). It maintains accurate date tracking through year 2099, including variable month lengths and day-of-week calculation - verified in the RTC registers per datasheet Table 1.

Can the X1288S16I-4.5AT1 generate multiple alarm interrupts simultaneously?

Yes, the X1288S16I-4.5AT1 supports two independent nonvolatile alarms (Alarm 0 and Alarm 1), each configurable to trigger on any combination of second, minute, hour, day-of-week, date, or month. Both alarms can assert simultaneously on the shared PHZ/IRQ pin, with individual status flags (AL0/AL1) in the Status Register for software discrimination.

What EEPROM protection mechanisms does the X1288S16I-4.5AT1 provide?

The X1288S16I-4.5AT1 implements BlockLock™ protection with eight software-selectable lock modes. These modes allow selective write-protection of EEPROM blocks (e.g., locking calibration constants while permitting user data writes), preventing accidental corruption during firmware updates or field operation - critical for certified utility and medical applications.