Renesas X4043S8I-4.5A

Overview

X4043S8I-4.5A from Intersil (now Renesas) is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 4kbit serial EEPROM in an 8-pin SOIC package. It features active-low RESET output, 4.5–4.75 V reset threshold, -40°C to +85°C operating range, and 400 kHz I²C interface - used in industrial microcontroller systems requiring reliable brownout protection and nonvolatile configuration storage.

For engineers reviewing the X4043S8I-4.5A datasheet, X4043S8I-4.5A pinout, X4043S8I-4.5A application, or X4043S8I-4.5A equivalent, key selection considerations include its programmable VTRIP threshold, Block Lock™ EEPROM protection, watchdog timeout configurability (200 ms / 600 ms / 1.4 s), low-power standby current (<1 µA with watchdog disabled), and compatibility with standard I²C bus timing.

Technical Context

The X4043S8I-4.5A implements a dual-function reset architecture: power-on reset asserts RESET for 250 ms after VCC stabilization, while low-VCC detection holds RESET active until VCC rises above 4.5 V and remains stable for 200 ms. Its watchdog timer monitors SDA/SCL activity using a state-machine-based transition detector, not clocked timing - restart requires full I²C START/STOP sequence.

EEPROM operation uses Intersil's Direct Write™ cell technology enabling 1,000,000 write cycles and 100-year data retention. Block Lock™ protection is controlled via nonvolatile BP2–BP0 bits, allowing selective locking of 16-byte to full-array segments, independent of WP pin state. The control register at address 1FFh (accessed via 1011 preamble) manages both watchdog and lock settings.

Key Specifications

Pinout & Package

Package: 8-lead SOIC (Pb-free, RoHS-compliant), JEDEC MS-012AC, body size 4.9 mm × 3.9 mm × 1.75 mm.

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 STM8AF6266TCY, the X4043S8I-4.5A delivers unique value through field-programmable VTRIP, 400 kHz I²C, and true standalone operation - enabling precise voltage-margin testing, faster configuration reads, and zero-firmware deployment in safety-critical embedded systems.

Availability

X4043S8I-4.5A is available at Aetrix Electronics and suitable for industrial automation, medical device, and automotive body electronics requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for X4043S8I-4.5A 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

Renesas Electronics Corporation (formerly Intersil) is a global semiconductor leader specializing in microcontrollers, analog, power, and mixed-signal solutions for industrial, automotive, and infrastructure markets.

The X4043S8I-4.5A belongs to Renesas' legacy CPU Supervisor family designed specifically for space-constrained embedded systems needing integrated reset, watchdog, and nonvolatile memory - eliminating discrete component count while maintaining MIL-STD-883 reliability benchmarks.

FAQ

What is the exact reset threshold voltage range for X4043S8I-4.5A?

The X4043S8I-4.5A has a factory-set VTRIP range of 4.5 V to 4.75 V, specified over the full -40°C to +85°C temperature range. This threshold is reprogrammable using a high-voltage (15–18 V) pulse applied to the WP pin during an I²C command sequence - allowing field adjustment for tighter system-level voltage margining. The X4043S8I-4.5A maintains RESET assertion validity down to VCC = 1 V, ensuring deterministic behavior during deep brownout conditions.

Does X4043S8I-4.5A support I²C clock stretching or multi-master arbitration?

No, the X4043S8I-4.5A does not support clock stretching or multi-master arbitration. It operates strictly as an I²C slave device with fixed 400 kHz maximum clock rate and standard START/STOP/ACK protocols. SDA and SCL inputs lack internal pull-ups, requiring external resistors; the device acknowledges only correctly addressed commands and ignores bus activity outside valid I²C framing. The X4043S8I-4.5A's watchdog timer monitors SDA/SCL transitions but does not participate in bus arbitration.

How is EEPROM write protection implemented in X4043S8I-4.5A?

X4043S8I-4.5A implements three-tiered EEPROM write protection: (1) hardware WP pin - HIGH disables all writes; (2) Block Lock™ bits (BP2–BP0) - nonvolatile settings lock 16-byte to full-array segments; (3) volatile WEL/RWEL latches - must be set before any control register or memory write. These layers operate independently: WP HIGH overrides all software locks, while BP bits remain effective even with WP LOW. The X4043S8I-4.5A's protection scheme prevents accidental overwrites during power transitions and firmware updates.

Can the watchdog timeout period of X4043S8I-4.5A be changed dynamically during system operation?

Yes, the watchdog timeout period of X4043S8I-4.5A can be changed dynamically via I²C writes to the nonvolatile control register (address 1FFh). The WD1/WD0 bits support four states: 200 ms, 600 ms, 1.4 s, or disabled. To modify the setting, the host MCU must first set WEL and RWEL latches using two preliminary I²C writes, then issue the final configuration byte - completing a 10 ms nonvolatile write cycle. The X4043S8I-4.5A retains the new timeout value across power cycles, enabling adaptive supervision strategies.

Is X4043S8I-4.5A pin-compatible with other members of the X4043/X4045 family?

Yes, X4043S8I-4.5A is pin-compatible with all 8-lead SOIC variants in the X4043/X4045 family, including X4043S8Z-4.5A (0°C to +70°C), X4045S8IZ-4.5A (active-high RESET), and X4043M8IZ-4.5A (MSOP package). Pin functions, electrical characteristics, and I²C protocol are identical across these variants - only temperature grade, RESET polarity, and package differ. The X4043S8I-4.5A shares identical PCB footprint and schematic symbol with X4043S8Z-4.5A, enabling drop-in replacement for extended temperature applications.