Renesas X5043S8

Overview

X5043S8 from Intersil (now Renesas) is a CPU supervisor IC integrating power-on reset, watchdog timer, supply voltage supervision, and 4K-bit SPI EEPROM in a single 8-lead SOIC package. It features a 4.63V ±2.5% reset threshold, selectable watchdog timeout (200ms/600ms/1.4s), and 512 × 8-bit EEPROM with block lock protection - deployed in industrial process controllers to ensure deterministic boot and data integrity during brownout events.

For engineers reviewing the X5043S8 datasheet, X5043S8 pinout, X5043S8 application, or X5043S8 equivalent, this page delivers verified technical context, validated pin functions, confirmed timing behavior under VCC dropout, and real-world substitution guidance for legacy system maintenance and BOM rationalization.

Technical Context

The X5043S8 implements a dual-function reset architecture: power-on reset asserts RESET/RESET for ≥200ms after VCC exceeds 4.63V, while low-VCC detection reasserts it if VCC drops below 4.63V and holds until VCC recovers and stabilizes for 200ms. Its watchdog circuit monitors CS/WDI transitions and triggers reset if no high-to-low edge occurs within the selected timeout window.

EEPROM operation uses standard SPI protocol (3.3MHz max) with MSB-first framing, 16-byte page writes, and nonvolatile status register control of both watchdog interval (WD0/WD1 bits) and memory block lock (BL0/BL1 bits). The Direct Write™ cell ensures ≥1M write cycles and 100-year data retention.

Key Specifications

Pinout & Package

Package: 8-lead SOIC (Pb-free, RoHS compliant), 150 mil width, JEDEC MS-012AC.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar CPU supervisor with integrated EEPROM applications.

Compared with MAX6361KA29+T and STM802LSD-46F, the X5043S8 uniquely combines field-reprogrammable VTRIP, 4K EEPROM with block lock, and 3.3MHz SPI - making it the only drop-in replacement for legacy designs requiring both precision supervision and robust nonvolatile storage in one footprint.

Availability

X5043S8 is available at Aetrix Electronics and suitable for industrial process controllers, network infrastructure equipment, and desktop motherboard designs requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for X5043S8 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 (acquired by Renesas Electronics in 2017) is a semiconductor company specializing in power management, precision analog, and interface ICs for industrial, communications, and computing markets.

The X5043S8 belongs to Intersil's CPU Supervisor family, designed specifically to consolidate reset, watchdog, voltage monitoring, and EEPROM into a single chip for space-constrained embedded systems where reliability and data integrity are mission-critical.

FAQ

What is the exact reset threshold voltage for X5043S8?

The X5043S8 has a factory-programmed VTRIP of 4.63V ±2.5%, corresponding to the "-4.5A" suffix in its ordering code. This value is guaranteed over temperature and can be reprogrammed to custom thresholds (e.g., 4.60V) using the VP=15–18V programming sequence documented in the FN8126 datasheet. The X5043S8 maintains reset assertion down to VCC = 1V and releases only after VCC exceeds VTRIP for 200ms.

Does X5043S8 support both active-low and active-high reset outputs?

No - the X5043S8 provides only an active-low open-drain RESET/RESET output. Its companion part X5045S8Z-4.5A offers active-high reset. The X5043S8 requires an external pull-up resistor (typically 4.7kΩ to VCC) to generate a valid logic-high level when inactive. This design allows flexible interfacing with MCUs that accept either polarity, provided the host-side logic interprets the open-drain signal correctly.

How does the watchdog timer in X5043S8 get reset?

The X5043S8 watchdog timer is reset exclusively by a high-to-low transition on the CS/WDI pin. Unlike some supervisors that accept toggles or pulses, the X5043S8 requires a full logic-level transition from VCC to VSS (or near-ground) within the selected timeout period (200ms/600ms/1.4s). If CS remains continuously high or low beyond that interval, RESET/RESET activates. The timeout value is set nonvolatilely via WD0/WD1 bits in the status register and persists across power cycles.

Can X5043S8 EEPROM be written while the watchdog is enabled?

Yes - the X5043S8 EEPROM write operations (byte or page) function independently of watchdog state. However, during a write cycle, the CS/WDI pin must remain stable (not toggled), so the watchdog cannot be serviced mid-write. To avoid timeout, firmware must complete all EEPROM writes within the watchdog window or disable the watchdog (via WD0/WD1 = 11b) before initiating extended write sequences. The WREN command and WP pin state govern write permission, not watchdog status.

What package variants are available for X5043S8?

The X5043S8 is offered exclusively in 8-lead SOIC (Small Outline Integrated Circuit) package, Pb-free and RoHS compliant, with 150-mil body width. It is not available in PDIP, MSOP, or TSSOP variants - those are designated under different part numbers (e.g., X5043PZ-4.5A for PDIP, X5043M8Z-4.5A for MSOP). The "S8" in X5043S8 explicitly denotes the SOIC-8 package per Intersil's ordering nomenclature.