Renesas X4165P

Overview

X4165P from Xicor (now Renesas) is a CPU supervisor IC integrating power-on reset control, watchdog timer, supply voltage supervision, and 16 Kbit serial EEPROM in a single 8-pin SOIC package. It features selectable watchdog timeout (200 ms / 600 ms / 1.4 s), four factory-standard V_TRIP thresholds (2.63 V / 2.93 V / 3.08 V / 4.38 V), and 400 kHz I²C-compatible 2-wire interface - used in embedded microcontroller systems for reliable boot sequencing and brownout protection.

For engineers reviewing the X4165P datasheet, X4165P pinout, X4165P application, or X4165P equivalent, key selection considerations include its dual-reset output polarity (active-HIGH RESET), programmable V_TRIP calibration capability, block-lock EEPROM protection granularity (64–512 bytes), and watchdog restart via SDA edge detection during SCL HIGH - all critical for safety-critical industrial controllers and legacy MCU platforms requiring deterministic reset behavior.

Technical Context

The X4165P implements a dedicated low-voltage detection comparator with hysteresis and a 250 ms reset timeout after V_CC recovery, ensuring stable processor initialization. Its watchdog timer uses SDA transition detection (HIGH→LOW while SCL=HIGH) as the refresh trigger, independent of clock source integrity.

EEPROM operation follows standard I²C protocol with byte- and 64-byte page-write modes, self-timed 5 ms typical write cycles, and hardware write protection enforced by WP pin + WPEN bit. The control register (address FFFFh) stores nonvolatile WD1/WD0 and BP2/BP1/BP0 bits, accessible only after volatile WEL/RWEL enable sequence.

Key Specifications

Pinout & Package

Package: 8-lead SOIC (JEDEC MS-012), 150 mil width, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with X4165P, MAX6361KA29+T offers lower cost but sacrifices V_TRIP calibration and memory size, while STM8AF6266TCX eliminates external components at the expense of design flexibility and qualification effort - making X4165P optimal for field-proven, hardware-determined reset architectures.

Availability

X4165P is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, automotive body control modules, and legacy industrial HMI panels requiring stable component supply and long-lifecycle support.

Supply support for X4165P 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

Xicor Inc. was a fabless semiconductor company specializing in nonvolatile memory and power management ICs, acquired by Intersil in 2001 and later integrated into Renesas Electronics.

The X4165P belongs to Xicor's CPU Supervisor + EEPROM family, designed specifically for embedded systems needing guaranteed boot integrity, brownout resilience, and secure parameter storage without MCU intervention.

FAQ

What is the reset output polarity of the X4165P?

The X4165P features an active-HIGH RESET output (pin 3), which differs from the active-LOW RESET/RESET output of the X4163P variant. This allows direct interfacing with microcontrollers requiring high-asserted reset signals, such as certain 8051 and PIC families, without external inverters or level-shifting circuitry. The X4165P datasheet confirms RESET remains asserted for 250 ms after V_CC stabilization and during watchdog timeout events.

Can the V_TRIP threshold of the X4165P be adjusted in-circuit?

Yes, the X4165P supports in-system V_TRIP calibration using a 12–15 V programming pulse applied to the WP pin while holding V_CC at the desired trip voltage. This nonvolatile adjustment enables precision tuning to ±50 mV without external components, verified by executing the "Set V_TRIP Level Sequence" defined in the X4165P datasheet. The procedure requires three I²C writes and completes within 10 ms.

How does the X4165P watchdog timer get refreshed?

The X4165P watchdog timer is refreshed by a HIGH-to-LOW transition on the SDA pin while SCL is held HIGH - matching the I²C start condition. This edge-sensitive mechanism ensures robustness against bus noise and avoids false timeouts during normal I²C communication. The timeout period (200 ms / 600 ms / 1.4 s) is set via nonvolatile WD1/WD0 bits and persists across power cycles.

What EEPROM protection mechanisms does the X4165P provide?

The X4165P implements three-tiered EEPROM write protection: (1) Software-enabled via WEL/RWEL latches, (2) Hardware-enforced via WP pin + WPEN bit (blocking all writes when both HIGH), and (3) Block Lock configurable through BP2/BP1/BP0 bits to protect 64–512 bytes or full array. These features prevent accidental overwrites of critical firmware parameters stored in the X4165P's 16 Kbit memory.

Is the X4165P pin-compatible with other devices in the X4163/5 family?

Yes, the X4165P shares identical 8-pin SOIC and TSSOP footprints and pin functions with X4163P and X4164P variants. The only functional difference is reset polarity: X4165P outputs active-HIGH RESET, while X4163P outputs active-LOW RESET/RESET. All share the same I²C address scheme, V_TRIP programming method, and EEPROM command set - enabling direct substitution where reset polarity matches system requirements.