Renesas X1226V8IZ

Overview

X1226V8IZ from Intersil is a 4K-bit (512 × 8) real-time clock/calendar IC with integrated 2-wire™ (I²C-compatible) interface, dual non-volatile alarms, on-chip oscillator compensation, and 512-byte EEPROM. It operates from 2.7–5.5V, draws 1.25µA typical operating current, and supports selectable frequency outputs (1Hz/4096Hz/32.768kHz) via the PHZ/IRQ pin. Used in utility meters and network infrastructure for accurate timekeeping with battery backup.

For engineers reviewing the X1226V8IZ datasheet, X1226V8IZ pinout, X1226V8IZ application, or X1226V8IZ equivalent, this page delivers verified technical context, validated pin functions, confirmed EEPROM block-lock protection modes, oscillator trim range (±30ppm digital + up to ±146ppm analog), and real-world alarm repeat behavior - all specific to the X1226V8IZ Pb-free TSSOP-8 variant.

Technical Context

The X1226V8IZ implements a fully autonomous RTC core synchronized to an external 32.768kHz crystal connected across X1/X2, with on-die oscillator compensation circuitry including a 64-position digitally controlled trim capacitor and six analog capacitance settings (3.25–18.75pF). Its dual alarm system supports match-based triggering on second/minute/hour/day-of-week/date/month with repeat mode enabled via the IM bit.

It uses a volatile status register (003Fh) with BAT, AL0/AL1, RWEL, WEL, and RTCF bits to manage power source detection, alarm flagging, and write-enable sequencing; nonvolatile alarm registers (0000h–000Fh) and control bits (0010h–0013h) reside in dedicated Clock/Control Register space accessible only after slave address 11011110b. The 512×8 EEPROM supports 64-byte page writes and eight BlockLock™ protection configurations.

Key Specifications

Pinout & Package

Package: 8-lead TSSOP (4.4mm width), RoHS-compliant Pb-free plus anneal finish, -40°C to +85°C operating temperature range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1337+T&R and PCF2129AT, the X1226V8IZ uniquely combines 512-byte EEPROM with hardware BlockLock™, dual alarms, and full on-die oscillator compensation - making it optimal for utility-grade metering and industrial logging where data integrity and long-term accuracy are non-negotiable.

Availability

X1226V8IZ is available at Aetrix Electronics and suitable for utility meters, HVAC controllers, and network infrastructure requiring stable component supply, extended temperature operation (-40°C to +85°C), and RoHS-compliant packaging.

Supply support for X1226V8IZ 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 X1226V8IZ belongs to Intersil's RTC family designed for high-accuracy, low-power timekeeping in metering, infrastructure, and embedded systems - emphasizing integrated compensation, nonvolatile alarms, and robust EEPROM security.

FAQ

What is the operating temperature range for the X1226V8IZ?

The X1226V8IZ is rated for -40°C to +85°C operation, matching its TSSOP-8 Pb-free package specification. This extended range ensures reliable RTC performance in outdoor utility meters, industrial HVAC units, and telecom base stations where ambient conditions vary widely. The on-chip oscillator compensation maintains timing accuracy across this full span without external calibration.

Does the X1226V8IZ require external load capacitors for the 32.768kHz crystal?

No, the X1226V8IZ integrates all oscillator compensation components, including a 64-position digitally controlled trim capacitor and six analog capacitance settings (3.25–18.75pF). This eliminates external load capacitors and reduces BOM count - confirmed in the FN8098 datasheet Section "Oscillator Compensation" and Figure 1. External crystal selection (e.g., Citizen CFS206-32.768KDZF) remains critical for baseline accuracy.

How does the X1226V8IZ handle leap year correction?

The X1226V8IZ implements automatic leap year correction through 2099, applying the Gregorian calendar rule: years divisible by 4 are leap years, except years divisible by 100 unless also divisible by 400. It correctly handles year 2000 as a leap year but does not correct for year 2100. This behavior is hard-coded in the calendar logic and requires no firmware intervention.

Can the X1226V8IZ operate solely from the VBACK supply?

Yes, the X1226V8IZ remains fully functional on VBACK alone when VCC is absent or below VBACK – 0.2V. In this mode, the RTC, alarms, and SRAM retain operation at reduced voltage (down to 1.8V), while EEPROM writes are disabled. The BAT bit in the Status Register (003Fh) indicates VBACK-only operation - enabling fail-safe timekeeping in battery-backed applications.

What happens to the RTC registers after a complete power failure affecting both VCC and VBACK?

After total power loss (both VCC and VBACK = 0V), the X1226V8IZ sets the RTCF bit in the Status Register (003Fh) to "1" and resets all RTC registers to default values (e.g., 00h for seconds, 01h for date). The clock halts until at least one byte is written to any RTC register, which clears RTCF and resumes counting. This prevents invalid time propagation post-failure.