Renesas X40420S14I-CT1

Overview

X40420S14I-CT1 from Xicor is a dual-voltage supervisor IC with integrated CPU reset controller, watchdog timer, battery backup switch, and 4kbit EEPROM. It monitors V_CC (V_TRIP1 = 4.6V ±1%) and V_2MON (V_TRIP2 = 2.9V ±1.7%), asserts active-HIGH RESET during brownout, delivers up to 50mA from V_CC to V_OUT, and supports I²C-compatible 400kHz serial interface - used in industrial process controllers for reliable power-fail detection and SRAM backup.

For engineers reviewing the X40420S14I-CT1 datasheet, X40420S14I-CT1 pinout, X40420S14I-CT1 application, or X40420S14I-CT1 equivalent, key selection criteria include its dual-threshold voltage monitoring accuracy, programmable watchdog timeout (25ms/200ms/1.4s), battery switchover hysteresis (±30mV), EEPROM block-lock protection, and 14-pin SOIC/TSSOP package compatibility.

Technical Context

The X40420S14I-CT1 implements two independent voltage comparators driving separate fail outputs (LOWLINE and V2FAIL), with factory-set trip points and optional reprogramming via high-voltage sequence on WDO. Its reset logic generates an active-HIGH open-drain RESET signal with user-selectable power-on delay (50/200/400/800ms) and manual reset debouncing.

Internally, it integrates a 4kbit (512 × 8) EEPROM with page-write capability (16-byte pages), Block Lock™ protection, and Direct Write™ cells rated for 100,000 write cycles and 100-year data retention. The battery switch uses a 5Ω (V_CC-to-V_OUT) and 80Ω (V_BATT-to-V_OUT) MOSFET pair with 60mV hysteresis to prevent oscillation during switchover.

Key Specifications

Pinout & Package

Package: 14-pin SOIC (Small Outline Integrated Circuit), RoHS-compliant, body width 3.9mm, lead pitch 1.27mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-voltage supervisor with EEPROM applications.

Compared with MAX6820EPA+ and TPS3823MPW, the X40420S14I-CT1 uniquely integrates dual-threshold monitoring, battery-backed V_OUT, and 4kbit EEPROM in one 14-pin SOIC - reducing component count by ≥4 parts and eliminating interconnect reliability risks in mission-critical systems.

Availability

X40420S14I-CT1 is available at Aetrix Electronics and suitable for industrial process controllers, network routers, medical diagnostic instruments, and automated test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for X40420S14I-CT1 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 X40420/X40421 product line was designed to consolidate power-on reset, watchdog, voltage supervision, and EEPROM into a single chip - targeting cost-sensitive, space-constrained embedded systems needing high reliability under variable supply conditions.

FAQ

What is the factory-default power-on reset timeout for X40420S14I-CT1?

The X40420S14I-CT1 ships with t_PURST = 200ms as the default power-on reset delay, controlled by PUP1/PUP0 bits (01 binary) in the nonvolatile control register. This value can be changed to 50ms, 400ms, or 800ms via I²C write to the control register at address 1FFh after enabling WEL and RWEL latches. The setting persists across power cycles and does not require reprogramming unless modified.

Does X40420S14I-CT1 support I²C standard-mode or fast-mode timing?

X40420S14I-CT1 supports I²C fast-mode operation up to 400kHz, as specified in its electrical characteristics. It meets standard-mode (100kHz) and fast-mode (400kHz) timing requirements for SCL low/high periods, setup/hold times, and pulse widths. The device uses open-drain SDA/SCL with internal weak pull-ups and requires external pull-up resistors (typically 2.2kΩ–4.7kΩ) to ensure proper bus rise time and noise immunity in mixed-voltage systems.

How does the battery switchover hysteresis work in X40420S14I-CT1?

X40420S14I-CT1 implements 60mV hysteresis around the V_BATT switchover point: V_OUT connects to V_BATT when V_CC falls below V_BATT – 0.03V, and reconnects to V_CC only when V_CC rises above V_BATT + 0.03V. This prevents oscillation during marginal supply conditions. The BATT-ON pin reflects this state with CMOS logic levels, enabling external transistor control for higher-current loads during normal operation.

Can the V_TRIP2 threshold of X40420S14I-CT1 be programmed below 1.6V?

Yes, the X40420S14I-CT1 allows V_TRIP2 programming down to 0.9V using the documented high-voltage sequence applied to the WDO pin. This requires applying the target voltage to V2MON, then issuing a START condition followed by slave address A0h, byte address 09h, and data byte 00h while holding V_p on WDO. The procedure is validated in the datasheet and does not affect EEPROM contents or other nonvolatile settings.

What happens to the EEPROM during a V_CC brownout event on X40420S14I-CT1?

During V_CC brownout below V_TRIP1, the X40420S14I-CT1 asserts RESET and disables all I²C communication - preventing accidental EEPROM writes. Built-in power-up/power-down protection circuitry blocks write commands when V_CC is outside 2.7V–5.5V, and the WEL latch powers up cleared. No EEPROM data is altered during brownout, and the 100-year retention specification remains valid as long as the device is operated within rated conditions before and after the event.