STMicroelectronics STM6321LWY6F

Overview

STM6321LWY6F from STMicroelectronics is a 5-pin precision voltage supervisor IC with integrated watchdog timer and manual reset input, designed for microprocessor power monitoring in industrial embedded systems. It monitors VCC at 3.3 V (±2.5%), asserts active-low open-drain RST for ≥1.4 ms upon fault, features 1.6 s watchdog timeout, and operates from –40 to +85 °C with 3 µA typical supply current.

For engineers reviewing the STM6321LWY6F datasheet, STM6321LWY6F pinout, STM6321LWY6F application, or STM6321LWY6F equivalent, key selection criteria include reset threshold accuracy, open-drain RST drive capability, MR input internal pull-up (52 kΩ), watchdog disable behavior (floating WDI), and guaranteed RST assertion down to VCC = 1.0 V.

Technical Context

The STM6321LWY6F implements a precision bandgap reference and comparator to monitor VCC against a fixed 3.3 V threshold (±2.5% over temperature). Its watchdog timer triggers reset if WDI remains static for ≥1.6 s (typ.), and resets on any WDI edge-enabling MCU health supervision without dedicated clock resources.

Reset assertion is guaranteed down to VCC = 1.0 V, and the open-drain RST output requires an external pull-up (e.g., 10 kΩ) to any supply ≤6 V. The MR input includes a 52 kΩ internal pull-up, supporting direct switch-to-ground connection without external components.

Key Specifications

Pinout & Package

STM6321LWY6F is housed in a standard 5-pin SOT23-5 package (JEDEC MO-178AB), with 1.3 mm × 2.9 mm footprint, 0.95 mm height, and gull-wing leads for surface-mount assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage supervisor with watchdog applications.

Compared with MAX6321US33D3+ and TPS3808G33DBVR, STM6321LWY6F uniquely combines open-drain RST, integrated MR pull-up, and ultra-low 3 µA supply current - making it optimal for cost-sensitive, multi-rail industrial designs requiring flexible reset signaling and long-term reliability.

Availability

STM6321LWY6F is available at Aetrix Electronics and suitable for industrial PLCs, smart energy meters, motor drive control boards, and medical diagnostic sensor hubs requiring stable component supply across extended product lifecycles.

Supply support for STM6321LWY6F 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, delivering automotive, industrial, and power management solutions with emphasis on reliability and longevity.

STM632x belongs to ST's precision supervisor IC product line, engineered specifically for robust power monitoring and watchdog supervision in harsh industrial environments where voltage stability and deterministic reset behavior are mission-critical.

FAQ

Can STM6321LWY6F be used with a 1.8 V microcontroller reset input?

Yes - its open-drain RST output is compatible with 1.8 V logic when pulled up to 1.8 V via an external resistor (e.g., 10 kΩ). The device guarantees RST assertion down to VCC = 1.0 V, and the output sink capability (≥2 mA at VCC = 1.8 V) ensures solid low-level drive into 1.8 V reset inputs without level shifters.

How is the watchdog function disabled on STM6321LWY6F?

The watchdog is disabled by leaving the WDI pin unconnected (floating). In this state, internal leakage (<10 µA) and capacitance (<200 pF) keep the timer serviced automatically. No external pull-up or pull-down is required - unlike alternatives that mandate tied-high or tied-low configurations to disable watchdog functionality.

What is the maximum allowable pull-up resistor value for the open-drain RST output?

The maximum recommended pull-up resistor is 100 kΩ when interfacing to CMOS inputs with ≤1 µA leakage, per Figure 11 in the datasheet. For standard 3.3 V MCU reset inputs (e.g., STM32), a 10 kΩ resistor ensures fast rise time (<100 ns) and noise immunity while maintaining <330 µA static current - balancing speed, power, and robustness.

Does STM6321LWY6F support reset pulse extension beyond 1.4 ms?

No - the reset pulse width is fixed at 1.4 ms (typ.) and cannot be adjusted externally. This value is trimmed during manufacturing and remains stable over temperature (±10% variation). For longer pulses, external monostable circuits or MCU firmware-based extension are required; the IC itself provides no programmable or adjustable timeout.