STMicroelectronics STM6821LWY6F

Overview

STM6821LWY6F from STMicroelectronics is a 5-pin precision voltage supervisor IC with integrated watchdog timer and manual reset input, designed for microprocessor reset management in embedded systems. It monitors VCC at 3.3 V (±2.5%), asserts active-low push-pull RST for ≥1.4 ms, features 1.6 s watchdog timeout, and guarantees reset assertion down to VCC = 1.0 V - used in industrial microcontroller power-up sequencing and fault recovery.

For engineers reviewing the STM6821LWY6F datasheet, STM6821LWY6F pinout, STM6821LWY6F application, or STM6821LWY6F equivalent, this page delivers verified technical context, exact pin functions, real-world use cases, and validated alternative parts - all grounded in ST's production datasheet DocID11110 Rev 14.

Technical Context

The STM6821LWY6F implements a precision bandgap reference and comparator to monitor VCC against a fixed 3.3 V threshold (±2.5% over –40 to +85 °C), with reset assertion guaranteed down to VCC = 1.0 V. Its internal watchdog timer triggers reset if WDI remains static for ≥1.6 s (typ.), and clears on any WDI edge (≥50 ns pulse width supported).

It provides one active-low push-pull RST output and one active-high push-pull RST output, both asserted synchronously during VCC brownout, MR low, or watchdog timeout. The MR input includes a 52 kΩ internal pull-up and supports direct switch-to-ground connection without external debounce.

Key Specifications

Pinout & Package

STM6821LWY6F is housed in a standard 5-pin SOT23-5 package (JEDEC MO-178AB), with 1.3 mm pitch, 2.9 mm × 1.6 mm body, and exposed pad not present. Pin 1 is marked by a dot or bevelled corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with STM6821LWY6F, STM6822LWY6F sacrifices the active-high RST output and push-pull drive for reduced cost and simpler reset topology, while TPS3808G125DBVR trades manual reset and dual outputs for tighter threshold tolerance - making STM6821LWY6F uniquely suited for industrial designs needing both reset polarities and field-serviceable reset capability.

Availability

STM6821LWY6F is available at Aetrix Electronics and suitable for industrial PLCs, medical infusion pumps, smart energy meters, and automotive body control modules requiring stable component supply across extended product lifecycles.

Supply support for STM6821LWY6F 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 silicon solutions for automotive, industrial, and embedded markets since 1987.

The STM6xxx family was engineered specifically for robust microprocessor supervision in harsh industrial environments - emphasizing guaranteed low-VCC operation, integrated watchdog, and minimal external components.

FAQ

Can STM6821LWY6F monitor a 5 V supply?

No - STM6821LWY6F is factory-trimmed for 3.3 V ±2.5% threshold detection. It cannot reliably supervise 5 V rails. For 5 V systems, ST offers STM6321 or STM6824 variants with 5 V thresholds, or consider discrete resistor-divider solutions with adjustable supervisors like TPS3808G50.

Is the watchdog timer enabled by default?

Yes - the watchdog is active upon power-up. It triggers reset if WDI remains static (high or low) for ≥1.6 s. To disable it, leave WDI floating or connect it to a tristate buffer output; leakage must stay below 10 µA and load capacitance under 200 pF.

What is the maximum capacitive load on the RST output?

The RST push-pull output drives up to 20 mA (absolute max), supporting typical MCU reset inputs with ≤50 pF load. For longer traces or multiple loads, verify rise/fall times remain within MCU's reset timing spec - ST characterizes performance up to 100 pF with <100 ns delay variation.

Does MR require external debouncing?

No - the MR input includes hysteresis and is compatible with mechanical switches directly connected to ground. ST confirms no external RC network is needed; however, in noisy environments (e.g., motor drives), a 0.1 µF capacitor from MR to GND improves immunity without affecting response time.