Renesas X4043S8I-2.7A

Overview

X4043S8I-2.7A from Intersil (now Renesas) is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 4kbit serial EEPROM in a single 8-pin SOIC package. It features active-low open-drain RESET output, selectable watchdog timeout (200 ms / 600 ms / 1.4 s), 2.7–5.5 V operation, 2.85–3.0 V reset threshold, and I²C-compatible 400 kHz 2-wire interface - used for microcontroller system reliability in industrial embedded controllers.

For engineers reviewing the X4043S8I-2.7A datasheet, X4043S8I-2.7A pinout, X4043S8I-2.7A application, or X4043S8I-2.7A equivalent, key selection considerations include its -40°C to +85°C temperature grade, factory-programmed 2.85–3.0 V VTRIP, Block Lock™ EEPROM protection, <1 µA standby current (watchdog OFF), and compatibility with standard I²C bus timing and pull-up requirements.

Technical Context

The X4043S8I-2.7A 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 2.85 V and remains stable for ≥200 ms. Its watchdog timer monitors SDA/SCL activity using a state-based transition detector - requiring valid I²C START/STOP sequences to reset, not just clock edges.

Internally, it combines a precision bandgap-based voltage reference for VTRIP sensing, a programmable nonvolatile control register (WD1/WD0, BP2/BP1/BP0), and a Direct Write™ EEPROM array with 1,000,000 write endurance and 100-year data retention. The device uses volatile WEL/RWEL latches to gate writes, ensuring inadvertent programming is blocked during brownout or power-up.

Key Specifications

Pinout & Package

Package: 8-pin SOIC (JEDEC MS-012AA), RoHS-compliant, Pb-free plus anneal finish, -40°C to +85°C operating range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6375US29D3+ and STM8T142M2U6, the X4043S8I-2.7A uniquely combines field-adjustable VTRIP, three watchdog timeout options, and 4 kbit Block Lock™ EEPROM in a single I²C slave - enabling higher system-level integration and long-term field calibration without hardware changes.

Availability

X4043S8I-2.7A is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, smart energy meters, and automotive body control modules requiring stable component supply across extended temperature and voltage ranges.

Supply support for X4043S8I-2.7A 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 Corporation, now part of Renesas Electronics, designs high-performance analog and mixed-signal ICs for industrial, communications, and computing applications.

The X4043/X4045 family was developed to consolidate power management, system supervision, and nonvolatile storage into one die - targeting space-constrained, reliability-critical embedded systems where discrete solutions increase failure risk and board cost.

FAQ

What is the reset output type and drive capability of the X4043S8I-2.7A?

The X4043S8I-2.7A features an active-low open-drain RESET output (Pin 3). It requires an external pull-up resistor to VCC and can sink up to 4 mA at VCC = 3.3 V. This design allows wired-OR connection with other reset sources and ensures compatibility with both 3.3 V and 5 V logic families when appropriately biased. The X4043S8I-2.7A RESET signal remains asserted until VCC exceeds 2.85 V and stabilizes for 200 ms.

Can the watchdog timeout period of the X4043S8I-2.7A be changed after soldering?

Yes, the watchdog timeout period of the X4043S8I-2.7A is configurable via nonvolatile WD1/WD0 bits in its control register. These bits can be rewritten in-system using the I²C interface and proper WEL/RWEL enable sequence - even after PCB assembly. Valid settings are 200 ms, 600 ms, 1.4 s, or disabled. The X4043S8I-2.7A retains the selected timeout across power cycles without external storage.

Does the X4043S8I-2.7A support standard I²C addressing and ACK protocols?

Yes, the X4043S8I-2.7A fully complies with standard I²C protocol: it responds to slave address 0xA0 (write) / 0xA1 (read) for EEPROM access and 0xB0 / 0xB1 for control register access. It issues ACK after valid address reception and data byte acceptance, supports repeated START, and handles clock stretching. The X4043S8I-2.7A also implements acknowledge polling to detect write completion without fixed delays.

How does the X4043S8I-2.7A protect EEPROM contents during power loss?

The X4043S8I-2.7A employs dual-layer EEPROM protection: (1) automatic hardware disable when VCC drops below VTRIP (2.85 V), halting all write operations mid-cycle, and (2) Block Lock™ software-configurable protection via BP2/BP1/BP0 bits. Additionally, the WP pin provides physical write inhibit. The X4043S8I-2.7A ensures no partial writes occur - if power fails during a 5 ms self-timed write, the EEPROM cell retains its pre-write state.

Is the VTRIP voltage of the X4043S8I-2.7A user-adjustable in the field?

Yes, the X4043S8I-2.7A supports in-field VTRIP reprogramming using a 15–18 V pulse applied to the WP pin during an I²C command sequence. This allows precise calibration to system-specific supply tolerances - for example, adjusting from the factory 2.85–3.0 V range to 2.92 V ±10 mV. The X4043S8I-2.7A retains the new threshold indefinitely and does not require external components or firmware changes to execute the procedure.