Renesas X4045S8I-2.7A

Overview

X4045S8I-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-high RESET output, 2.7V–5.5V operation, 2.85V–3.0V reset threshold, -40°C to +85°C temperature range, and I²C-compatible 2-wire interface - used in embedded microcontroller systems requiring reliable brownout protection and nonvolatile configuration storage.

For engineers reviewing the X4045S8I-2.7A datasheet, X4045S8I-2.7A pinout, X4045S8I-2.7A application, or X4045S8I-2.7A equivalent, key selection considerations include its programmable VTRIP threshold, Block Lock™ EEPROM protection granularity, watchdog timeout options (200ms/600ms/1.4s), <1µA standby current with watchdog disabled, and compatibility with standard I²C bus timing at up to 400kHz.

Technical Context

The X4045S8I-2.7A implements a dedicated low-voltage detection circuit that asserts RESET when VCC falls below 2.85V and holds it active until VCC exceeds 3.0V for ≥200ms. Its watchdog timer monitors SDA/SCL activity using a state-machine-based transition detector - requiring valid I²C start/stop sequences to reset, not just clock edges.

Internally, the device combines three independent functional blocks: a precision bandgap-based VTRIP comparator with factory-trimmed hysteresis, a self-timed EEPROM write engine supporting 16-byte page writes with 5ms typical cycle time, and a nonvolatile control register (at 1FFh) storing WD1/WD0 and BP2/BP1/BP0 bits - all accessible via the same 2-wire interface without address conflicts.

Key Specifications

Pinout & Package

Package: 8-pin SOIC (JEDEC MS-012, 150 mil width), RoHS-compliant Pb-free plus anneal finish.

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 STM8T142M2U6, the X4045S8I-2.7A uniquely balances field-programmable VTRIP, large 4kbit I²C EEPROM, and hardware-based watchdog restart - enabling flexible brownout tuning, external host configuration management, and glitch-immune supervision without MCU intervention.

Availability

X4045S8I-2.7A 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 temperature and long product lifecycles.

Supply support for X4045S8I-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, automotive, and communications applications - emphasizing reliability, precision, and long-term supply stability.

The X4045S8I-2.7A belongs to Intersil's CPU Supervisor family, engineered specifically for microcontroller-based systems needing coordinated power sequencing, fault detection, and nonvolatile parameter storage - targeting applications where firmware robustness and data integrity are mission-critical.

FAQ

What is the reset output polarity and drive capability of the X4045S8I-2.7A?

The X4045S8I-2.7A provides an active-high open-drain RESET output on Pin 3. It requires an external pull-up resistor (typically 4.7kΩ to VCC) and can sink up to 4mA while asserting reset. This configuration ensures compatibility with most microcontrollers' active-high reset inputs and allows multiple devices to share a common reset rail via wired-OR connection. The X4045S8I-2.7A does not offer push-pull or active-low variants in this specific ordering suffix.

Can the VTRIP threshold of the X4045S8I-2.7A be reprogrammed in-system, and what voltage is required?

Yes, the VTRIP threshold of the X4045S8I-2.7A can be reprogrammed in-system using a high-voltage pulse applied to the WP pin. A 15–18V programming voltage (VP) must be supplied to WP while issuing a specific I²C command sequence (Slave Address A0h, Byte Address 01h, Data 00h). The X4045S8I-2.7A supports both upward and downward VTRIP adjustment, with final accuracy verified by ramping VCC and measuring actual reset assertion voltage.

How does the watchdog timer in the X4045S8I-2.7A differ from standard I²C clock-based watchdogs?

The X4045S8I-2.7A watchdog timer uses a state-transition detector on SDA and SCL rather than counting clock edges - it requires a complete I²C transaction (START → SCL LOW → SCL HIGH → STOP) to reset. This prevents false timeouts caused by noise-induced clock pulses or partial bus activity. The X4045S8I-2.7A watchdog timeout is selectable among 200ms, 600ms, and 1.4s via nonvolatile WD1/WD0 bits, and defaults to disabled after power-up.

What EEPROM protection mechanisms are implemented in the X4045S8I-2.7A?

The X4045S8I-2.7A implements three-tiered EEPROM protection: (1) hardware WP pin - HIGH disables all writes; (2) power-on/power-down detection - blocks writes during VCC transitions; (3) Block Lock™ software protection - eight configurable zones (0 to 128 bytes, upper 1/4, full array, etc.) controlled by nonvolatile BP2/BP1/BP0 bits. These protections operate independently and concurrently, ensuring robust defense against accidental or malicious overwrites of critical configuration data stored in the X4045S8I-2.7A.

Is the X4045S8I-2.7A compatible with standard I²C buses operating at 100kHz and 400kHz?

Yes, the X4045S8I-2.7A fully complies with standard I²C Fast-mode specifications up to 400kHz. Its SDA and SCL inputs include built-in noise filtering and meet I²C timing requirements for setup, hold, and pulse widths across the full -40°C to +85°C temperature range. The X4045S8I-2.7A supports standard I²C addressing (1010xxx0 for memory, 1011xxx0 for control register), ACK polling during write cycles, and multi-master arbitration - making it interoperable with any I²C host controller without protocol translation.