Renesas X4163S8

Overview

X4163S8 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 an 8-lead SOIC package. It provides selectable watchdog timeout (200 ms/600 ms/1.4 s), low-V_CC reset assertion down to 1 V, and 400 kHz 2-wire interface - used in microcontroller-based embedded systems for reliable boot sequencing and data retention.

For engineers reviewing the X4163S8 datasheet, X4163S8 pinout, X4163S8 application, or X4163S8 equivalent, key selection concerns include reset threshold programmability, EEPROM page-write capability, watchdog independence from firmware, active-low/high reset output behavior, and hardware write protection via WP pin and BP bits.

Technical Context

The X4163S8 implements a dual-mode reset architecture: power-on reset with 250 ms delay and brownout detection with 200 ms hysteresis, both asserting RESET/RESET until V_CC stabilizes above V_TRIP. Its watchdog timer monitors SDA transitions during SCL HIGH and supports three nonvolatile timeout settings (200 ms, 600 ms, 1.4 s) or disable mode.

EEPROM functionality includes 2K × 8-bit organization, 64-byte page write mode, self-timed 5 ms typical write cycle, and multi-level write protection: power-up/down circuitry, volatile WEL/RWEL latches, nonvolatile block lock (BP2–BP0), and hardware WP/WPEN control - all accessible via standard I²C protocol at 400 kHz.

Key Specifications

Pinout & Package

Package: 8-lead JEDEC SOIC (3.9 mm × 4.9 mm, 1.27 mm pitch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361KA29+T and STM8AF6266TCY, the X4163S8 uniquely combines field-programmable reset threshold, hardware watchdog with multiple timeouts, and 16 Kbit EEPROM in a single 8-pin SOIC - reducing BOM count and eliminating firmware dependencies for critical safety functions.

Availability

X4163S8 is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic devices, automotive body control modules, smart energy meters, and battery-powered IoT edge nodes requiring stable component supply and long-term obsolescence support.

Supply support for X4163S8 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 Renesas Electronics in 2008.

The X4163/5 product line was designed to consolidate reset supervision, watchdog protection, and serial EEPROM into a single chip for space-constrained microcontroller systems - targeting cost-sensitive, reliability-critical embedded applications.

FAQ

What is the function of the WP pin on the X4163S8?

The WP (Write Protect) pin on the X4163S8 enables hardware-level write protection when used with the nonvolatile WPEN bit. When both WP and WPEN are HIGH, writes to protected memory blocks and the control register are blocked. Additionally, applying 12–15 V to WP (with V_CC at desired V_TRIP) initiates programmable reset threshold adjustment - a unique feature not found in most supervisors. This dual-role design simplifies board layout and enhances system security.

How does the X4163S8 watchdog timer operate independently of firmware?

The X4163S8 watchdog timer monitors SDA transitions while SCL is HIGH - a hardware-level detection of I²C bus activity that requires no firmware interaction. If no falling edge occurs on SDA within the selected timeout (200 ms/600 ms/1.4 s), RESET/RESET is asserted. Because this logic resides entirely within the X4163S8, it remains functional even if the MCU freezes, executes invalid instructions, or loses clock signal - ensuring fail-safe recovery without software dependency.

Can the reset threshold voltage of the X4163S8 be changed after soldering to the PCB?

Yes, the V_TRIP threshold of the X4163S8 can be reprogrammed post-assembly using a controlled voltage pulse on the WP pin. With V_CC set to the desired trip point (e.g., 3.0 V), applying 12–15 V to WP for <100 µs initiates nonvolatile threshold programming. This field-adjustable capability allows fine-tuning for board-specific supply tolerances or aging effects - eliminating the need for multiple BOM variants or external resistor dividers typically required with fixed-threshold supervisors.

What EEPROM write protection mechanisms does the X4163S8 provide?

The X4163S8 implements five-tiered EEPROM write protection: (1) Power-up/down circuitry inhibits writes during supply transients; (2) Volatile WEL latch must be set before any write; (3) Nonvolatile BP2–BP0 bits lock memory blocks (full array, first 8 pages, etc.); (4) Hardware WP/WPEN combination disables all writes when enabled; (5) RESET/RESET assertion terminates in-progress writes and blocks new access. These layers ensure robust data integrity in harsh environments where voltage glitches or EMI could corrupt stored parameters.

Is the X4163S8 pin-compatible with other members of the X4163/5 family?

Yes, the X4163S8 shares identical pinout and electrical characteristics with all X4163/5 variants including X4165S8, differing only in RESET/RESET output polarity (active LOW vs. active HIGH). Both use the same 8-lead SOIC package, I²C addressing scheme, control register map, and programming sequences. This allows direct substitution in existing designs when output polarity matches system requirements - simplifying inventory management and enabling design reuse across product families.