STMicroelectronics STWD100YNPWY3F

Overview

STWD100YNPWY3F from STMicroelectronics is an automotive-qualified watchdog timer IC that monitors microcontroller operation by detecting software hangs or hardware faults. It features four selectable timeout periods (3.4 ms, 6.3 ms, 102 ms, and 1.6 s), 13 µA typical supply current, open-drain or push-pull WDO output, and a dedicated chip enable (EN) input. It operates across –40 to 125 °C and is used in engine control units to prevent unsafe system lockups.

For engineers reviewing the STWD100YNPWY3F datasheet, STWD100YNPWY3F pinout, STWD100YNPWY3F application, or STWD100YNPWY3F equivalent, key selection criteria include timeout flexibility, EN-controlled activation, automotive-grade temperature and qualification, low-power operation, and compatibility with bidirectional MCU reset pins.

Technical Context

The STWD100YNPWY3F implements a self-contained, single-chip watchdog timer with no external components required. Its internal counter resets on valid transitions at WDI (low-to-high only), pulses ≥1 µs on EN, or WDO toggling - all validated under –40 to 125 °C and 2.7–5.5 V supply.

It supports two WDO configurations: open-drain (requiring external pull-up) and push-pull (with VOH ≥0.8VCC at ISOURCE = 500 µA). The EN pin has an internal 32–100 kΩ pull-down and enables/disable functionality; floating EN activates the device, while a ≥1 µs high pulse resets the timer.

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 TPS3823-33DBVR and MAX6373KA+T, STWD100YNPWY3F uniquely combines AEC-Q100 qualification, four factory-set timeouts, EN pin control, and ultra-low 13 µA current - making it the only drop-in solution for ASIL-B-compliant automotive MCUs requiring flexible, low-power, and robust supervision.

Availability

STWD100YNPWY3F is available at Aetrix Electronics and suitable for engine control units, ADAS domain controllers, and electric power steering systems requiring stable component supply across extended automotive lifecycles.

Supply support for STWD100YNPWY3F 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, analog ICs, power devices, and sensors for automotive, industrial, and consumer markets.

The STWD100 product line delivers highly reliable, low-power watchdog timers specifically engineered for functional safety-critical automotive subsystems operating across harsh thermal and electrical environments.

FAQ

What is the exact watchdog timeout period for STWD100YNPWY3F?

The STWD100YNPWY3F is the "xY" variant, specifying a nominal watchdog timeout period of 1.6 seconds (min 1.12 s, max 2.24 s at TA = –40 to 125 °C and VCC = 2.7–5.5 V). This value is factory-trimmed and non-adjustable; timeout selection is determined solely by the part number suffix (xP = 3.4 ms, xW = 6.3 ms, xX = 102 ms, xY = 1.6 s).

Does STWD100YNPWY3F support both open-drain and push-pull WDO outputs?

No - the output configuration is fixed per device variant and defined at manufacture. STWD100YNPWY3F uses open-drain WDO output, requiring an external pull-up resistor (typically 10 kΩ to ≤6 V). Push-pull variants exist (e.g., STWD100YNWWY3F) but are distinct order codes; mixing configurations risks incorrect reset signaling and system instability.

How does the EN pin behave during power-up?

At power-up, if EN remains low while VCC rises above VSTART (1.9–2.7 V), the watchdog timer starts counting immediately. If EN transitions high within tWD after VCC exceeds VSTART, WDO stays high for the duration of the EN pulse plus tWD. The EN pin has an internal 32–100 kΩ pull-down, so leaving it unconnected enables the device by default - no external resistor is needed.

Can STWD100YNPWY3F interface directly with a bidirectional MCU reset pin?

Yes, but only with a 4.7 kΩ series resistor between WDO and the MCU reset I/O, as specified in ST's Figure 5. This prevents signal contention when both the MCU and STWD100 attempt to drive the line. Direct connection without the resistor risks latch-up or undefined reset states, especially during MCU boot sequences where reset direction may change dynamically.