Renesas X4045M8

Overview

X4045M8 from Intersil is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 4kbit EEPROM in an 8-pin MSOP package. It features active-high RESET output, 4.5–4.75V reset threshold, 400kHz I²C interface, <1µA standby current (watchdog off), and Block Lock™ EEPROM protection. It is used in embedded microcontroller systems requiring reliable brownout detection and nonvolatile configuration storage.

For engineers reviewing the X4045M8 datasheet, X4045M8 pinout, X4045M8 application, or X4045M8 equivalent, key selection criteria include reset polarity (active-high), VTRIP tolerance (±125mV), EEPROM endurance (1M cycles), watchdog timeout options (200ms/600ms/1.4s), and MSOP-8 thermal performance in space-constrained industrial controllers.

Technical Context

The X4045M8 implements a dual-stage reset architecture: power-on reset asserts RESET for 250ms after VCC stabilization, while low-VCC detection holds RESET active until VCC exceeds VTRIP for 200ms. Its watchdog timer monitors SDA/SCL activity using a state machine that resets only on valid I²C start/stop sequences - not arbitrary pin toggling.

EEPROM operation uses Intersil's Direct Write™ cell technology with 16-byte page write mode and self-timed 5ms typical write cycle. Block Lock™ protection is controlled via nonvolatile BP2–BP0 bits, enabling selective locking of 16–128 byte segments or full array, independent of WP pin state.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (Pb-free, RoHS-compliant), 3.0mm × 3.0mm footprint, 0.65mm pitch, JEDEC MO-187 variant.

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 STM8AF5288TDY, the X4045M8 uniquely delivers field-programmable VTRIP, 1M-cycle EEPROM, and validated I²C watchdog restart - making it optimal for calibrated industrial sensors and medical devices where reset accuracy and data integrity are non-negotiable.

Availability

X4045M8 is available at Aetrix Electronics and suitable for industrial PLC I/O modules, medical infusion pump controllers, smart energy meters, automotive body control modules, and safety-critical embedded systems requiring stable component supply and long-term obsolescence management.

Supply support for X4045M8 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) is a U.S.-based semiconductor designer specializing in precision analog, power management, and interface ICs for industrial, aerospace, and medical markets.

The X4045M8 belongs to Intersil's CPU Supervisor family, engineered to consolidate reset, watchdog, voltage monitoring, and nonvolatile storage into a single die - reducing system BOM count and improving reliability in mission-critical embedded control applications.

FAQ

What is the reset polarity and output type of the X4045M8?

The X4045M8 provides an active-high open-drain RESET output on pin 3. This means the pin pulls low during normal operation and goes high-impedance when reset is asserted - requiring an external pull-up resistor to the host MCU's supply rail (typically 3.3V or 5V). The X4045M8 differs from the X4043 series by using active-high logic, simplifying interface design with MCUs lacking dedicated active-low reset inputs. This behavior is fixed and cannot be inverted in-circuit.

Can the reset threshold voltage (VTRIP) of the X4045M8 be modified after soldering?

Yes, the X4045M8 supports field reprogramming of its VTRIP voltage using a 15–18V pulse applied to the WP pin while issuing specific I²C commands. The procedure allows adjustment to ±10mV precision and is fully supported in-system without removing the X4045M8 from the PCB. This capability is unique to the X4045M8 among legacy supervisors and eliminates the need for multiple SKUs when fine-tuning reset points for different power supply tolerances.

How does the watchdog timer in the X4045M8 detect MCU failure?

The X4045M8 watchdog timer monitors SDA and SCL lines for valid I²C protocol transitions - specifically requiring a complete start condition (SDA high→low while SCL high), followed by clock pulses and a stop condition. It does not respond to arbitrary pin toggling. This design prevents false timeouts caused by bus noise or partial communication errors. The timeout period (200ms/600ms/1.4s) is set via nonvolatile WD1/WD0 bits and remains unchanged across power cycles unless explicitly rewritten.

What EEPROM protection mechanisms does the X4045M8 provide beyond the WP pin?

In addition to the hardware WP pin, the X4045M8 implements Block Lock™ protection via three nonvolatile BP2–BP0 bits, enabling eight distinct lock configurations - from protecting just the first 16 bytes (e.g., boot parameters) to locking the entire 512-byte array. These bits are written through the I²C interface using a secure three-step sequence involving WEL and RWEL latches. Unlike simple WP-based locking, Block Lock™ remains effective even when WP is grounded, providing defense-in-depth against firmware update errors.

Is the X4045M8 still in active production or has it been discontinued?

The X4045M8Z-4.5A variant is marked "No longer available" in the official Intersil (Renesas) ordering table, with X4045S8Z-4.5A (SOIC-8) listed as the recommended replacement. However, Aetrix Electronics maintains legacy inventory and offers extended lifecycle support for the X4045M8, including traceable lots, obsolescence forecasting, and cross-reference engineering assistance for migration to the SOIC-8 pin-compatible alternative while preserving identical electrical functionality and firmware interface.