Renesas X4043PI-2.7

Overview

X4043PI-2.7 from Intersil (now Renesas) is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 4kbit EEPROM in a single 8-pin PDIP package. It features active-low RESET output, 2.7–5.5V operation, 2.55–2.7V reset threshold, and 400kHz I²C interface - used in microcontroller-based embedded systems requiring reliable brownout protection and nonvolatile configuration storage.

For engineers reviewing the X4043PI-2.7 datasheet, X4043PI-2.7 pinout, X4043PI-2.7 application, or X4043PI-2.7 equivalent, key selection considerations include its programmable VTRIP threshold, Block Lock™ EEPROM protection, watchdog timeout options (200ms/600ms/1.4s), <1µA standby current with watchdog disabled, and compatibility with legacy through-hole PCB layouts using PDIP-8.

Technical Context

The X4043PI-2.7 implements a dual-function reset architecture: power-on reset asserts RESET for ≥250ms after VCC stabilization, while low-VCC detection holds RESET active until VCC rises above 2.55–2.7V and remains stable for 200ms. Its watchdog timer monitors SDA/SCL activity and triggers reset if no valid I²C transaction occurs within the selected timeout period.

Internally, it integrates a 512 × 8-bit EEPROM array with Direct Write™ cells (1M write cycles, 100-year retention), accessed via standard 2-wire I²C protocol (slave address 0xA0 for writes, 0xA1 for reads). The control register at 0x1FF enables nonvolatile configuration of watchdog timing and block lock protection bits (BP2–BP0), set only after volatile WEL/RWEL latching sequence.

Key Specifications

Pinout & Package

Package: 8-pin PDIP (Plastic Dual In-line Package), through-hole mount, RoHS-compliant (Pb-free plus anneal).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361LKA27+T and STM8T142M2U6, the X4043PI-2.7 uniquely delivers field-adjustable VTRIP, full 4kbit EEPROM with Block Lock™, and PDIP-8 compatibility - making it optimal for legacy industrial designs needing upgradeable brownout precision and robust nonvolatile storage without MCU integration.

Availability

X4043PI-2.7 is available at Aetrix Electronics and suitable for industrial control panels, medical instrumentation, smart metering, and automotive body electronics requiring stable component supply and long-lifecycle support.

Supply support for X4043PI-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

Intersil Corporation, now part of Renesas Electronics, designs high-performance analog and mixed-signal ICs for power management, precision sensing, and system supervision.

The X4043/X4045 family was developed to consolidate reset, watchdog, voltage monitoring, and EEPROM into one die - reducing bill-of-materials cost and PCB area in microcontroller-based systems where reliability and configurability are critical.

FAQ

What is the factory-default watchdog timeout setting for the X4043PI-2.7?

The X4043PI-2.7 ships with watchdog disabled (WD1=1, WD0=1) as the factory default. This prevents unintended resets during initial system bring-up. To enable watchdog functionality, the user must first set WEL and RWEL bits via the I²C interface, then write the desired timeout value (00=1.4s, 01=600ms, 10=200ms) to the control register at address 0x1FF. The X4043PI-2.7 retains this setting across power cycles due to nonvolatile storage of WD1/WD0 bits.

Can the X4043PI-2.7's reset threshold voltage be reprogrammed in-circuit?

Yes, the X4043PI-2.7 supports in-system VTRIP reprogramming using a 15–18V pulse applied to the WP pin while issuing specific I²C commands (slave address 0xA0, byte address 0x01, data 0x00). This allows field adjustment of the reset threshold between 2.55V and 2.7V without removing the device. The X4043PI-2.7 requires VCC to be set to the target threshold voltage during programming, and the procedure does not affect EEPROM contents or control register settings.

Does the X4043PI-2.7 support I²C clock stretching or multi-master arbitration?

No, the X4043PI-2.7 does not support I²C clock stretching or multi-master arbitration. It operates strictly as a slave device with fixed timing parameters: SCL frequency up to 400kHz, setup/hold times compliant with Fast-mode I²C specifications, and no internal clock hold capability. The X4043PI-2.7 relies on the master controller to manage bus arbitration and timing; any attempt to stretch SCL will result in communication failure or timeout.

What happens to the X4043PI-2.7's RESET output during a brownout event?

During a brownout event where VCC falls below the programmed VTRIP (2.55–2.7V), the X4043PI-2.7 immediately asserts its active-low RESET output and holds it asserted until VCC rises above VTRIP and remains stable for ≥200ms. The X4043PI-2.7 guarantees RESET remains valid down to VCC = 1V, ensuring clean reset signaling even during deep undervoltage conditions. This behavior is independent of watchdog status or EEPROM activity.

Is the X4043PI-2.7 pin-compatible with other members of the X4043/X4045 family?

Yes, the X4043PI-2.7 is pin-compatible with all X4043 and X4045 variants in the same 8-pin PDIP package, including X4043PIZ-2.7, X4043PIZ-2.7A, and X4043PIZ-4.5A. All share identical pinout (NC/NC/RESET/VSS/SDA/SCL/WP/VCC), electrical characteristics, and functional architecture. The X4043PI-2.7 differs only in factory-programmed VTRIP range (2.55–2.7V) and temperature grade (0°C to 70°C), allowing direct substitution where those parameters meet design requirements.