Renesas X4323S8I

Overview

X4323S8I from Xicor (now part of Renesas) is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 32Kbit serial EEPROM in a single 8-lead SOIC package. It features four selectable V_CC reset thresholds (2.63V/2.93V/3.08V/3.30V), 400kHz I²C-compatible 2-wire interface, and <20µA standby current with watchdog enabled - used in microcontroller-based embedded systems for reliable boot sequencing and brownout protection.

For engineers reviewing the X4323S8I datasheet, X4323S8I pinout, X4323S8I application, or X4323S8I equivalent, key selection criteria include programmable V_TRIP threshold adjustment, nonvolatile watchdog timeout configuration (200ms/600ms/1.4s), 64-byte page write capability, hardware write protection via WP pin, and operation across 2.7V–5.5V supply range.

Technical Context

The X4323S8I implements a dual-function reset architecture: power-on reset asserts RESET for ≥250ms after V_CC stabilization, while low-V_CC detection holds RESET active until V_CC exceeds V_TRIP for 200ms and remains above 1V. Its watchdog timer monitors SDA transitions during SCL HIGH to detect MCU lockup.

Reset assertion is open-drain (active-low), compatible with both NMOS and CMOS logic families. The integrated 32Kbit EEPROM supports byte and 64-byte page writes with self-timed 5ms typical write cycles, and includes block lock protection (1–8 pages, full array, or none) controlled by nonvolatile BP bits.

Key Specifications

Pinout & Package

Package: 8-lead JEDEC SOIC (SO-8), 150 mil width, surface-mount. Pin 1 marked by notch or dot; pin numbering follows standard counterclockwise layout.

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 X4323S8I uniquely integrates programmable voltage supervision, multi-interval watchdog, and high-speed EEPROM in one SOIC-8 package - reducing component count, board space, and qualification effort for safety-critical embedded systems.

Availability

X4323S8I is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, automotive body control modules, smart energy meters, and battery-backed data loggers requiring stable component supply and long-term lifecycle support.

Supply support for X4323S8I 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

Xicor was a fabless semiconductor company specializing in nonvolatile memory and power management ICs, acquired by Renesas Electronics in 2008. Known for innovation in EEPROM-integrated supervisors and programmable voltage references.

The X4323/5 product line was designed to consolidate reset, watchdog, voltage monitoring, and EEPROM functions into a single chip for microcontroller-based systems - targeting reliability-critical applications where board space, BOM count, and power efficiency are constrained.

FAQ

What is the default watchdog timeout setting for the X4323S8I?

The X4323S8I ships with watchdog disabled (WD1=1, WD0=1). This is the factory-default state and remains unchanged until explicitly configured via the Control Register. To enable watchdog functionality, the MCU must execute the three-step write sequence to set WD1/WD0 to 00 (1.4s), 01 (600ms), or 10 (200ms). The X4323S8I will not assert RESET due to watchdog timeout unless this configuration is performed and the WP pin is not actively blocking register writes.

Can the X4323S8I's reset threshold voltage be adjusted after soldering to the PCB?

Yes, the X4323S8I supports in-system V_TRIP reprogramming using a 12–15V pulse applied to the WP pin while holding V_CC at the desired threshold voltage. This procedure requires no special equipment beyond a programmable power supply and HV pulse generator, and can be performed post-assembly to fine-tune brownout response for specific board-level voltage droop characteristics. The X4323S8I retains the new V_TRIP value indefinitely in nonvolatile circuitry.

How does hardware write protection work on the X4323S8I?

Hardware write protection on the X4323S8I requires both the WP pin HIGH and the WPEN bit (bit 7 of Control Register) set to 1. When both conditions are met, all EEPROM writes and Control Register modifications are blocked - even if WEL is set. This protection is independent of software state and persists through power cycles. The X4323S8I cannot be reconfigured without first pulling WP LOW to disable hardware lock, making it ideal for securing bootloader regions or calibration data against runtime corruption.

What is the maximum EEPROM write endurance and data retention for the X4323S8I?

The X4323S8I EEPROM is rated for 100,000 write/erase cycles per memory location and guarantees data retention for 100 years at +25°C. These specifications are validated across the full operating temperature range (–40°C to +85°C), with retention degrading predictably at elevated temperatures (e.g., ~40 years at +85°C). The X4323S8I implements automatic wear leveling at the page level during 64-byte writes, extending effective endurance in applications with frequent small-data updates.

Does the X4323S8I support I²C bus arbitration or multi-master operation?

No, the X4323S8I operates exclusively as an I²C slave device and does not implement bus arbitration logic. It expects a single master to control SCL and initiate all transactions. While multiple X4323S8I devices can share the same bus using unique S0/S1 combinations (up to four per bus), simultaneous master-driven operations - such as clock stretching or arbitration - are not supported. The X4323S8I responds only to valid START/STOP sequences and acknowledges only correctly addressed commands.