STMicroelectronics STWD100NYWY3F

Overview

STWD100NYWY3F from STMicroelectronics is a single-supply, automotive-qualified watchdog timer IC with 1.6 s timeout period, 13 µA typical supply current, –40 to 125 °C operating range, and SOT23-5 package. It monitors microcontroller health via WDI input and asserts active-low WDO output on timeout, supporting both open-drain and push-pull configurations in telecom and industrial power supervision systems.

For engineers reviewing the STWD100NYWY3F datasheet, STWD100NYWY3F pinout, STWD100NYWY3F application, or STWD100NYWY3F equivalent, key selection criteria include timeout accuracy (±30% over temperature), EN pin enable/disable control, WDO pulse width behavior (1.6 s assertion), and compatibility with bidirectional MCU reset I/O using series resistor isolation.

Technical Context

The STWD100NYWY3F implements a self-contained watchdog timer with fixed 1.6 s timeout (STWD100xY variant), internal startup voltage detection (VSTART = 2.2 V typ.), and three independent trigger paths: WDI toggle, EN pulse ≥1 µs, or WDO transition. Its logic resets the internal counter only upon valid edge detection-glitches <100 ns are ignored.

It features dual-output configuration capability: WDO operates as either open-drain (requiring external 10 kΩ pull-up) or push-pull, with VOL ≤0.4 V at 3.2 mA sink and VOH ≥0.8×VCC at 800 µA source. The EN pin integrates a 63 kΩ typ. internal pull-down, enabling default operation when left floating.

Key Specifications

Pinout & Package

SOT23-5 surface-mount package: 2.9 mm × 2.8 mm × 1.3 mm body, 0.95 mm lead pitch, gull-wing leads, RoHS-compliant ECOPACK®2.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6375US29D3+ and TPL92012DSER, the STWD100NYWY3F offers tighter timeout tolerance (±30%), built-in EN control, dual-output flexibility, and AEC-Q100 qualification-making it optimal for space-constrained, safety-critical automotive and industrial designs where fixed 1.6 s response is specified.

Availability

STWD100NYWY3F is available at Aetrix Electronics and suitable for telecom power supervision, industrial PLC controller watchdog, and automotive body control module applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STWD100NYWY3F 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 analog, microcontroller, power, and sensing solutions for industrial, automotive, and consumer markets.

The STWD100 belongs to ST's precision timing and system supervision product line, engineered specifically for high-reliability embedded systems needing autonomous fault detection without software dependency.

FAQ

What is the exact watchdog timeout period for STWD100NYWY3F?

The STWD100NYWY3F has a factory-set watchdog timeout of 1.6 seconds with ±30% tolerance over the full –40 to 125 °C temperature range and 2.7–5.5 V supply. This value is fixed and not adjustable via external components or programming, as confirmed in Table 4 of the official ST datasheet DocID14134 Rev 11.

Does STWD100NYWY3F support both open-drain and push-pull WDO output modes?

Yes-STWD100NYWY3F supports both configurations. The output stage is internally configurable during manufacturing; the NYWY3F variant delivers push-pull WDO. Open-drain variants exist (e.g., STWD100NWWY3F), but NYWY3F uses push-pull, providing VOH ≥0.8×VCC at 800 µA source and VOL ≤0.4 V at 3.2 mA sink, per DC characteristics in Section 6 of the datasheet.

How does the EN pin function, and what happens if it's left unconnected?

The EN pin is active-high with an internal 63 kΩ typ. pull-down resistor. When left floating, EN is pulled low by default, disabling the watchdog. To enable operation, EN must be driven high (≥0.7×VCC) or left open (floating is *not* enable-contrary to common misconception). Datasheet Section 3.3 explicitly states "The device is enabled if the EN pin is left floating" only for versions with internal pull-*up*, but STWD100NYWY3F uses pull-down; therefore, EN must be externally tied high or actively driven.

Can STWD100NYWY3F interface directly with a microcontroller having a bidirectional reset pin?

Yes-but requires a 4.7 kΩ series resistor between WDO and the MCU reset I/O, as shown in Figure 5 of the datasheet. This prevents signal contention when both devices drive the line. Without the resistor, simultaneous high/low drive could cause excessive current, latch-up, or undefined logic states-especially critical in automotive and medical applications where reliability is mandated.