STMicroelectronics STWD100YNWWY3F

Overview

STWD100YNWWY3F from STMicroelectronics is an automotive-qualified watchdog timer IC that monitors microcontroller operation via WDI input and asserts active-low WDO output on timeout, with selectable 3.4 ms, 6.3 ms, 102 ms, or 1.6 s timeout periods, 13 µA typical supply current, and –40 to 125 °C operating range for use in engine control units and ADAS power management.

For engineers reviewing the STWD100YNWWY3F datasheet, STWD100YNWWY3F pinout, STWD100YNWWY3F application, or STWD100YNWWY3F equivalent, key selection criteria include timeout period selection, EN pin enable/disable control, open-drain vs. push-pull WDO configuration, and AEC-Q100 qualification for automotive systems requiring fail-safe reset supervision.

Technical Context

The STWD100YNWWY3F implements a self-contained watchdog timer with independent internal timing circuitry, triggered by WDI transitions (low-to-high on all versions; high-to-low also supported on Y-series), and resettable via EN pin pulses ≥1 µs. It features dual-mode WDO output-configurable as open-drain (requiring external pull-up) or push-pull-with minimum 10 µs assertion width after timeout.

Its EN pin integrates an internal 32–100 kΩ pull-down resistor and enables functional disable of watchdog behavior when held low; device powers up enabled if EN floats. Startup occurs at VSTART = 1.9–2.7 V, and it operates across 2.7–5.5 V supply with guaranteed timing over –40 to 125 °C.

Key Specifications

Pinout & Package

SOT23-5 package: 2.9 mm × 1.3 mm × 1.0 mm body, surface-mount, lead-free, RoHS-compliant, ECOPACK®2 rated.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3823-33DBVR and MAX6373KA29+T, the STWD100YNWWY3F uniquely combines AEC-Q100 qualification, four factory-set timeouts, EN pin disable, and 2.7–5.5 V operation - making it the only drop-in solution for automotive systems requiring both flexibility and functional safety compliance.

Availability

STWD100YNWWY3F is available at Aetrix Electronics and suitable for engine control units, ADAS domain controllers, and body control modules requiring stable component supply, long-term automotive lifecycle support, and traceable AEC-Q100 qualified parts.

Supply support for STWD100YNWWY3F 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 automotive, industrial, and consumer markets.

The STWD100 product line delivers automotive-grade watchdog timers optimized for functional safety-critical subsystems where deterministic hardware reset supervision is mandated by ISO 26262.

FAQ

What is the function of the EN pin on the STWD100YNWWY3F?

The EN pin enables or disables the watchdog timer function. It features an internal 32–100 kΩ pull-down resistor; leaving it floating enables the device, while pulling it low disables watchdog operation entirely. A ≥1 µs high pulse on EN resets the internal timer, providing hardware-initiated recovery without toggling WDI.

Can the WDO output drive a microcontroller reset pin directly?

Yes - when configured as push-pull, WDO drives actively high/low and interfaces directly with standard MCU reset inputs. In open-drain mode, a 10 kΩ external pull-up to any supply ≤6 V is required. For bidirectional reset pins, a 4.7 kΩ series resistor isolates WDO from contention, as specified in ST's application guidance.

How does the STWD100YNWWY3F handle power-up sequencing?

At power-up, the internal timer starts counting once VCC exceeds the startup threshold (1.9–2.7 V). If WDI is not toggled before the selected timeout expires, WDO asserts low. The device requires no external initialization and begins supervision autonomously after VCC stabilization - critical for fail-safe boot in automotive systems.

Is the STWD100YNWWY3F pin-compatible with other STWD100 variants?

Yes - all STWD100 variants (including STWD100NWWY3F, STWD100YNXWY3F, etc.) share identical SOT23-5 pinout, electrical characteristics, and functional behavior. Only timeout period and qualification grade differ; no PCB redesign is needed when selecting alternate versions for timing or automotive compliance needs.