Renesas X4323S8I-2.7

Overview

X4323S8I-2.7 from Xicor (now Renesas) is a CPU supervisor IC integrating power-on reset control, selectable watchdog timer, supply voltage supervision, and 32 Kbit serial EEPROM in a single 8-pin SOIC package. It operates from 2.7V to 5.5V, asserts reset down to V_CC = 1V, supports 400 kHz I²C interface, and delivers <20 µA standby current with watchdog enabled - used in embedded microcontroller systems requiring reliable boot sequencing and nonvolatile configuration storage.

For engineers reviewing the X4323S8I-2.7 datasheet, X4323S8I-2.7 pinout, X4323S8I-2.7 application, or X4323S8I-2.7 equivalent, key selection criteria include its programmable V_TRIP threshold (factory-set at 2.7V), 64-byte page write EEPROM, three watchdog timeout options (200 ms / 600 ms / 1.4 s), Block Lock protection granularity, and open-drain active-low RESET output with 250 ms release delay.

Technical Context

The X4323S8I-2.7 implements a dual-function reset architecture: power-on reset generation with 250 ms timeout and low-V_CC detection using an adjustable comparator with hysteresis. Its watchdog timer monitors SDA transitions during SCL HIGH to detect MCU lockup, with timeout period set by nonvolatile WD1/WD0 bits in the control register.

EEPROM functionality uses a 4K × 8-bit array organized in 64-byte pages, supporting byte and page writes with self-timed 5 ms typical write cycles. Write protection combines volatile WEL/RWEL latches, nonvolatile BP2–BP0 block lock bits, and hardware WP pin + WPEN bit enabling full-array or page-level locking.

Key Specifications

Pinout & Package

Package: 8-pin JEDEC SOIC (SO-8), body size 3.9 mm × 4.9 mm, lead pitch 1.27 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361KA27+T and STM8T142M2U6, the X4323S8I-2.7 uniquely balances field-programmable voltage supervision, multi-option watchdog timing, and high-density EEPROM in a minimal 8-pin footprint - making it optimal for space-constrained, field-deployed equipment requiring post-manufacturing calibration and long-term reliability.

Availability

X4323S8I-2.7 is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, smart metering, and automotive body electronics requiring stable component supply, long-lifecycle support, and guaranteed traceability.

Supply support for X4323S8I-2.7 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. Its legacy products emphasize reliability, low-power operation, and system integration.

The X4323/5 product line was designed to consolidate reset, watchdog, voltage monitoring, and EEPROM functions into a single chip for microcontroller-based systems - reducing board area, bill-of-materials count, and qualification effort in safety-critical embedded applications.

FAQ

What is the factory-set reset threshold voltage for X4323S8I-2.7?

The X4323S8I-2.7 ships with a factory-programmed V_TRIP of 2.7V, meaning RESET/RESET asserts when V_CC falls below this level and remains active until V_CC rises above 2.7V and stabilizes for 250 ms. This threshold is stored in nonvolatile circuitry and remains stable over temperature and time unless explicitly reprogrammed using the VP pulse method described in the datasheet. The X4323S8I-2.7 supports reprogramming to custom values between ~1.7V and ~4.4V.

Can the watchdog timer on X4323S8I-2.7 be disabled after power-up?

Yes, the watchdog timer on X4323S8I-2.7 can be disabled after power-up by writing WD1=1 and WD0=1 to the control register (address FFFFh), which sets the timeout period to "disabled" per Table 1. This requires executing the three-step write sequence (02h → 06h → 03h) with proper WEL and RWEL latching. Once disabled, the X4323S8I-2.7 will not assert RESET/RESET due to watchdog timeout, though power-on and low-V_CC reset functions remain fully operational.

How does the X4323S8I-2.7 protect EEPROM writes during power loss?

The X4323S8I-2.7 protects EEPROM writes during power loss through multiple mechanisms: (1) RESET/RESET asserts below V_TRIP, halting all I²C communication; (2) in-progress writes complete before RESET activation; (3) WEL latch powers up LOW, blocking writes until explicitly enabled; and (4) Block Lock bits prevent accidental overwrites of critical sectors. These features ensure that partial or corrupted writes do not occur during brownout, making the X4323S8I-2.7 suitable for mission-critical data storage.

What is the maximum I²C clock frequency supported by X4323S8I-2.7?

The X4323S8I-2.7 supports standard-mode and fast-mode I²C operation up to 400 kHz, as confirmed in the Features section and Electrical Characteristics table. This allows efficient transfer of calibration data or configuration parameters without monopolizing the bus. The SDA and SCL pins meet I²C specification timing requirements including setup/hold times and rise/fall characteristics, and require external pull-up resistors sized per bus capacitance - a requirement consistent across all operating voltages from 2.7V to 5.5V.

Does X4323S8I-2.7 support page write operations, and what is the page size?

Yes, the X4323S8I-2.7 supports 64-byte page write operations, allowing up to 64 sequential bytes to be written in a single I²C transaction. This reduces protocol overhead significantly compared to byte writes and improves EEPROM update efficiency - especially valuable when storing multi-byte sensor calibration tables or firmware metadata. Page boundaries are aligned to 64-byte intervals (e.g., 0x0000–0x003F), and writes crossing a boundary automatically wrap within the same page, as documented in Figure 10 of the datasheet.