Renesas X4043S8I

Overview

X4043S8I from Intersil is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 4kbit serial EEPROM with Block Lock™ protection. It features active-low open-drain RESET output, 4.5–4.75V reset threshold (VTRIP), -40°C to +85°C operating temperature, and 400kHz I²C interface - used in industrial microcontroller systems requiring reliable brownout detection and nonvolatile configuration storage.

For engineers reviewing the X4043S8I datasheet, X4043S8I pinout, X4043S8I application, or X4043S8I equivalent, key selection considerations include its programmable VTRIP threshold, 200ms reset timeout, 16-byte page write EEPROM, watchdog timeout options (200ms/600ms/1.4s), and SOIC-8 package compatibility with legacy 8-pin supervisory designs.

Technical Context

The X4043S8I implements a dual-function reset architecture: power-on reset asserts RESET for ≥250ms after VCC stabilization, while low-VCC detection holds RESET active until VCC exceeds VTRIP (4.5–4.75V) for ≥200ms. Its watchdog timer monitors SDA/SCL activity and triggers reset if no valid I²C transaction occurs within the selected timeout interval.

EEPROM operation uses Intersil's Direct Write™ cell technology (1M write cycles, 100-year retention) with software-configurable block lock protection (BP2–BP0 bits) and hardware WP pin control. All memory and register writes require volatile WEL/RWEL latching prior to nonvolatile programming.

Key Specifications

Pinout & Package

Package: 8-lead SOIC (Pb-free, RoHS-compliant, JEDEC standard).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361KA29+T and STM8T142M2U6, the X4043S8I uniquely combines field-programmable VTRIP, 4kbit EEPROM with page-write efficiency, and I²C-compatible watchdog restart - making it optimal for industrial upgrades where pin-compatible replacement and EEPROM scalability matter.

Availability

X4043S8I is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, automotive body electronics, and smart metering applications requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for X4043S8I 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 interface ICs for industrial, aerospace, and communications markets.

The X4043S8I belongs to Intersil's CPU Supervisor family designed to consolidate reset, watchdog, voltage monitoring, and nonvolatile storage into a single 8-pin package - targeting space-constrained embedded systems needing high reliability and field-adjustable thresholds.

FAQ

What is the factory-default VTRIP setting for the X4043S8I?

The X4043S8I ships with a factory-default VTRIP threshold of 4.5V to 4.75V, optimized for use with 4.5–5.5V VCC supplies. This value is stored in nonvolatile memory and remains stable over temperature and time unless explicitly reprogrammed using the high-voltage WP pin sequence described in the FN8118 datasheet. The X4043S8I maintains this setting across power cycles without drift.

Does the X4043S8I support I²C clock stretching or multi-master arbitration?

No, the X4043S8I does not support I²C clock stretching or multi-master arbitration. It operates strictly as a standard-mode I²C slave device with fixed 400kHz maximum clock rate. The SCL input is purely synchronous - no internal clock hold capability - and the device does not monitor bus arbitration signals. Its I²C interface is designed for simple master-slave communication in resource-constrained embedded systems.

Can the watchdog timer on the X4043S8I be disabled after power-up?

Yes, the watchdog timer on the X4043S8I can be disabled after power-up by writing '11' to the WD1/WD0 bits in the nonvolatile control register (address 1FFh). This setting persists across power cycles. Disabling requires executing the three-step WEL/RWEL write sequence; once disabled, the watchdog will not assert RESET regardless of SDA/SCL activity, but power-on and low-VCC reset functions remain fully operational.

How does the X4043S8I handle EEPROM writes during brownout conditions?

The X4043S8I halts all EEPROM write operations when VCC falls below VTRIP. While RESET is asserted, the I²C interface is disabled and no new commands - including writes - are accepted. Any write in progress when VCC drops below threshold is allowed to complete, but new writes are blocked until VCC rises above VTRIP and stabilizes for 200ms. This prevents partial or corrupted EEPROM updates during unstable supply conditions.

Is the X4043S8I pin-compatible with the X4045S8IZ-4.5A?

Yes, the X4043S8I is pin-compatible with the X4045S8IZ-4.5A - both use identical 8-lead SOIC packaging and share identical pin functions (RESET, VSS, SDA, SCL, WP, VCC). The only functional difference is reset polarity: X4043S8I provides active-low RESET, while X4045S8IZ-4.5A provides active-high RESET. No PCB changes are required for substitution, but firmware must account for inverted reset logic signaling.