Renesas X4325S8

Overview

X4325S8 from Xicor (now 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 provides active-low reset assertion down to V_CC = 1V, selectable watchdog timeout (200 ms / 600 ms / 1.4 s), and 400 kHz 2-wire interface - used in embedded microcontroller systems requiring reliable boot sequencing and nonvolatile configuration storage.

For engineers reviewing the X4325S8 datasheet, X4325S8 pinout, X4325S8 application, or X4325S8 equivalent, key selection criteria include its programmable V_TRIP threshold (adjustable via VP on WP pin), block-lock EEPROM protection (1–8 pages or full array), and dual reset output polarity support (X4325 variant provides active-HIGH RESET).

Technical Context

The X4325S8 implements a dedicated low-voltage detection circuit with four factory-standard V_TRIP thresholds (2.63V, 2.93V, 3.08V, 4.65V) and user-programmable trip point via nonvolatile programming sequence using 12–15V on WP. Its watchdog timer monitors SDA transitions during SCL HIGH and offers three fixed timeout intervals controlled by nonvolatile WD1/WD0 bits.

Reset generation combines power-on delay (250 ms), brownout recovery (200 ms hold after V_CC > V_TRIP), and watchdog fault response. The 32Kbit EEPROM operates in 64-byte page write mode with self-timed 5 ms typical write cycle and built-in write protection logic including WEL/RWEL latches, Block Protect bits (BP2–BP0), and hardware WPEN-enabled lock.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361KA29+T, X4325S8 delivers programmable V_TRIP, 4× faster I²C, and double EEPROM capacity - critical for adaptive brownout response and high-frequency parameter updates. Against STM8AF6266TCY, X4325S8 offers simpler qualification, deterministic reset timing, and zero MCU firmware dependency.

Availability

X4325S8 is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, automotive body control modules, smart energy meters, and battery-backed IoT gateways requiring stable component supply across extended product lifecycles.

Supply support for X4325S8 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 2002. Its legacy products remain widely deployed in industrial and automotive systems.

The X4325S8 belongs to Xicor's CPU Supervisor with EEPROM family, designed specifically to reduce board space and improve reliability in microcontroller-based systems by integrating reset, watchdog, voltage monitoring, and configuration storage into one IC.

FAQ

What is the reset output polarity of the X4325S8?

The X4325S8 provides an active-HIGH RESET output, distinct from the X4323 variant which outputs active-LOW. This matches the reset input requirements of most contemporary microcontrollers without needing external inversion circuitry. The RESET pin is open-drain and requires an external pull-up resistor to V_CC; it asserts during power-on (250 ms), brownout (V_CC < V_TRIP), or watchdog timeout. The X4325S8 datasheet confirms this behavior in the PIN FUNCTION table and PRINCIPLES OF OPERATION section.

How is the V_TRIP threshold adjusted on the X4325S8?

The V_TRIP threshold on the X4325S8 is adjusted using a nonvolatile programming sequence that applies 12–15V to the WP pin while holding V_CC at the desired trip voltage. This requires setting the WEL bit, then executing a specific two-byte write (A0h followed by 00h or 03h) with VP applied. The procedure is detailed in Figures 1–4 of the X4325S8 datasheet and allows precise customization beyond the four factory defaults (2.63V, 2.93V, 3.08V, 4.65V).

Does the X4325S8 support page writes to its EEPROM?

Yes, the X4325S8 supports 64-byte page write mode for its 32Kbit EEPROM. After sending the slave address and word address, the master may transmit up to 64 consecutive data bytes; the internal address counter auto-increments within the page. Each byte receives an ACK, and the internal write cycle begins only after the STOP condition. This reduces I²C transaction overhead versus byte-by-byte writes and is confirmed in the "Page Write" section of the X4325S8 datasheet (page 9).

What watchdog timeout periods are available on the X4325S8?

The X4325S8 offers three selectable watchdog timeout periods: 200 ms, 600 ms, and 1.4 s - configured via nonvolatile WD1 and WD0 bits in the control register (FFFFh). These intervals are fixed per configuration and persist across power cycles. The watchdog is disabled by default (WD1=1, WD0=1) and enabled by writing appropriate values. The timeout is reset by a falling edge on SDA while SCL is HIGH, as specified in the WATCHDOG TIMER section of the X4325S8 datasheet.

How does hardware write protection work on the X4325S8?

Hardware write protection on the X4325S8 activates when both the WP pin is driven HIGH and the WPEN bit in the control register is set to 1. When enabled, it blocks all writes to block-protected EEPROM regions and prevents modification of the block protect bits themselves. This provides robust immunity against corruption during power transients or software faults. The X4325S8 datasheet states this behavior is "hardware write protected" and distinguishes it from software-only protection using BP bits alone.