Renesas X5643P

Overview

X5643P from Intersil is a CPU supervisor IC integrating power-on reset control, selectable watchdog timer, low-voltage detection with reprogrammable 4.5V reset threshold, and 64Kbit SPI EEPROM - all in a single 8-lead PDIP package. It asserts active-low RESET down to VCC = 1V, supports 2MHz SPI (modes 0,0 & 1,1), delivers <1µA standby current with watchdog disabled, and enables block-lock protection for 0–100% of EEPROM memory.

For engineers reviewing the X5643P datasheet, X5643P pinout, X5643P application, or X5643P equivalent, this device serves as a system-level reliability enhancer in microcontroller-based embedded systems requiring brownout immunity, fail-safe restart logic, nonvolatile configuration storage, and in-circuit programmable voltage threshold tuning.

Technical Context

The X5643P implements a dual-function CS/WDI pin that serves both chip select and watchdog input, with HIGH-to-LOW transitions restarting the timer. Its reset logic combines power-on reset (active to 1V, 200ms timeout) and low-VCC supervision using an internal comparator with 20mV hysteresis and user-reprogrammable trip point.

EEPROM operation uses Intersil's Direct Write™ cell architecture (100k write cycles, 100-year retention) and supports 32-byte page writes with self-timed 5ms typical write cycles. The status register includes volatile WIP and FLAG bits plus nonvolatile WD0/WD1 (watchdog timeout selection), BL0/BL1 (block lock), and WPEN (in-circuit ROM mode enable).

Key Specifications

Pinout & Package

Package: 8-lead Plastic Dual In-Line Package (PDIP), 0.300" wide body, 0.100" lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6900 and STM802L, the X5643P uniquely combines field-programmable reset voltage, 64Kbit EEPROM with block lock, and ultra-low-power watchdog - enabling single-chip system supervision without design compromises on flexibility or reliability.

Availability

X5643P is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, automotive body control modules, smart energy meters, and battery-backed embedded systems requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for X5643P 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 analog, and interface applications.

The X5643P belongs to Intersil's CPU Supervisor family, engineered to consolidate reset, watchdog, voltage monitoring, and nonvolatile storage into one die - targeting cost-sensitive, space-constrained embedded systems where system-level reliability is non-negotiable.

FAQ

What is the default reset threshold voltage for the X5643P?

The X5643P is specified as the 4.5V variant (X5643-4.5A), with a standard reset threshold of 4.5V (min 4.5V, typ 4.63V, max 4.75V). This value is factory-set but can be reprogrammed to any voltage between 1.7V and 5.0V using the VTRIP programming sequence with VP pulses on SCK and SI pins.

How does the X5643P distinguish between a watchdog timeout and a low-voltage reset?

The X5643P uses a volatile FLAG bit in its status register to indicate reset source: it is set automatically on watchdog timeout and cleared on power-on or low-VCC reset. Host firmware reads this bit via RDSR instruction after reset to execute appropriate recovery - e.g., full reboot vs. parameter reload - without external logic.

Can the X5643P's EEPROM be written while the watchdog timer is enabled?

Yes - the X5643P allows concurrent EEPROM writes and watchdog operation. During a write cycle, the WIP bit becomes '1' and remains so until completion; the watchdog timer continues counting independently. However, CS/WDI must still be toggled within the selected timeout period to prevent reset assertion.

What package options are available for the X5643P?

The X5643P is offered in 8-lead PDIP (plastic dual in-line package) per the FN8135 datasheet. While the X5643/X5645 family also includes a 14-lead SOIC variant, the 'P' suffix specifically denotes the PDIP version - confirmed by ordering information and pin configuration diagrams in the datasheet.

Does the X5643P support SPI mode 0,1 or 1,0?

No - the X5643P supports only SPI modes 0,0 (CPOL=0, CPHA=0) and 1,1 (CPOL=1, CPHA=1), as explicitly stated in the FEATURES section. Attempting mode 0,1 or 1,0 will result in incorrect data sampling due to mismatched clock polarity and phase timing relative to SI/SO edges.