STMicroelectronics STWD100NXWY3F

Overview

STWD100NXWY3F from STMicroelectronics is a single-supply, automotive-qualified watchdog timer IC with fixed timeout options (3.4 ms, 6.3 ms, 102 ms, or 1.6 s), 13 µA typical supply current, and –40 to 125 °C operating range. It features WDI input for periodic reset, EN pin for chip enable/disable, and configurable open-drain or push-pull WDO output - used in telecom power supervision and industrial control systems to recover locked microcontrollers.

For engineers reviewing the STWD100NXWY3F datasheet, STWD100NXWY3F pinout, STWD100NXWY3F application, or STWD100NXWY3F equivalent, key selection criteria include timeout period matching, EN pin logic behavior, WDO output configuration (open-drain vs. push-pull), temperature grade compliance, and SOT23-5 package compatibility with existing PCB footprints.

Technical Context

The STWD100NXWY3F implements a self-contained watchdog timer with internal oscillator-based timing, independent of system clock sources. Its timeout period is factory-fixed to 1.6 s (as indicated by 'Y' in the order code), and it resets only upon valid WDI toggle, EN pulse ≥1 µs, or WDO transition - not via VCC ramp alone.

Operation requires no external components: EN has an internal 32–100 kΩ pull-down resistor, enabling watchdog functionality when left floating; WDO asserts low after timeout and sustains for ≥140 ms (t_PW = 140–280 ms) regardless of subsequent WDI activity on this variant.

Key Specifications

Pinout & Package

SOT23-5 package: 5-pin, surface-mount, 2.9 mm × 2.8 mm × 1.3 mm body, ECOPACK®-compliant, lead-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar watchdog timer applications.

Compared with MAX6375US29+T and TPS3823-33DBVR, STWD100NXWY3F uniquely combines AEC-Q100 qualification, 1.6 s timeout, EN pin controllability, and ultra-low 13 µA current - making it optimal for automotive and industrial systems requiring precise, robust, and power-efficient watchdog supervision.

Availability

STWD100NXWY3F is available at Aetrix Electronics and suitable for telecom power supervision, industrial PLC control, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STWD100NXWY3F 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The STWD100 product line delivers highly reliable, low-power watchdog timers specifically engineered for mission-critical embedded systems where deterministic hardware-level fault recovery is mandatory.

FAQ

What is the factory-configured timeout period for STWD100NXWY3F?

The 'Y' in the order code STWD100NXWY3F indicates a factory-set timeout period of 1.6 seconds. This value is laser-trimmed during manufacturing and cannot be altered in-circuit. It is verified per Table 4 of the datasheet (DocID14134 Rev 11), with min/typ/max values of 1.12 s / 1.6 s / 2.24 s at VCC = 2.7–5.5 V and TA = –40 to 125 °C.

Can STWD100NXWY3F be used with a 3.3 V microcontroller's bidirectional reset pin?

Yes - STWD100NXWY3F supports interfacing with bidirectional reset I/O using a 4.7 kΩ series resistor between WDO and the MCU pin, as shown in Figure 5 of the datasheet. This prevents signal contention when both devices drive the line. The WDO output must be configured as open-drain (not push-pull) for safe bidirectional operation.

Does STWD100NXWY3F require an external pull-up resistor on WDO?

Only if configured for open-drain output. The datasheet specifies a 10 kΩ pull-up to any supply ≤6 V is sufficient in most cases. For push-pull operation, no external pull-up is needed - WDO actively drives high and low. Configuration is determined by internal metal option during wafer fabrication and is fixed per part number.

Is the EN pin of STWD100NXWY3F compatible with 1.8 V logic levels?

No - the EN pin threshold is referenced to VCC: VIH = 0.7×VCC and VIL = 0.3×VCC (Table 4). With VCC = 3.3 V, VIH ≈ 2.31 V minimum; with VCC = 2.7 V, VIH ≈ 1.89 V. A 1.8 V logic high may not reliably enable the device and is outside guaranteed operating conditions per the datasheet.