Nexperia USA Inc. STM6821MWY6F

Overview

STM6821MWY6F from STMicroelectronics is a 5-pin precision voltage supervisor IC with integrated watchdog timer and manual reset input, designed for microprocessor reset management in industrial 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 power-sensitive MCU boot sequencing and fault recovery circuits.

For engineers reviewing the STM6821MWY6F datasheet, STM6821MWY6F pinout, STM6821MWY6F application, or STM6821MWY6F equivalent, key selection criteria include its guaranteed 1.0 V reset hold, 3 µA typical supply current, SOT23-5 package compatibility, and dual reset output configuration (RST and RST) enabling flexible interface with bidirectional MCU reset pins.

Technical Context

The STM6821MWY6F 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).

It provides two independent reset outputs: active-low push-pull RST and active-high push-pull RST - both asserted simultaneously during VCC undervoltage, MR low, or watchdog timeout. The MR input includes a 52 kΩ internal pull-up, supporting direct switch-to-ground connection without external components.

Key Specifications

Pinout & Package

STM6821MWY6F is housed in a standard 5-pin SOT23-5 package (JEDEC MO-178AA), with 1.27 mm pitch, 2.9 mm × 1.6 mm body, and exposed pad not connected internally.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM6821MWY6F, STM6822MWY6F sacrifices RST output and push-pull drive for open-drain flexibility, while TPS3808G33DBVR trades dual outputs and ultra-low ICC for adjustable watchdog timing and broader vendor support - neither matches the combined precision threshold, dual-RST, and sub-µA operation of the STM6821MWY6F.

Availability

STM6821MWY6F is available at Aetrix Electronics and suitable for industrial PLC controllers, smart metering units, medical sensor hubs, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM6821MWY6F 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, specializing in microcontrollers, power management, analog, and sensing solutions for industrial, automotive, and consumer markets.

The STM6xxx series is ST's dedicated family of precision voltage supervisors targeting robust, low-power microprocessor reset management - engineered specifically for deterministic fault recovery in harsh industrial and safety-critical embedded environments.

FAQ

What is the exact reset threshold voltage and tolerance for STM6821MWY6F?

The STM6821MWY6F has a nominal VCC reset threshold of 3.3 V with a tolerance of ±2.5% over the full operating temperature range (–40 to +85 °C), as specified in Table 6 of the official datasheet (DocID11110 Rev 14). This value is factory-trimmed and does not require external calibration.

Can the watchdog function be disabled, and how?

Yes, the watchdog function can be disabled by leaving the WDI pin unconnected (floating) or connecting it to a tristate buffer output. In either case, the internal watchdog timer is serviced automatically within the 1.6 s timeout period, preventing unintended reset assertion - no software or external hardware changes are needed.

Does STM6821MWY6F support interfacing with MCUs that have bidirectional reset pins?

Yes, it supports bidirectional MCU reset pins via its dual RST/RST outputs. To prevent contention, ST recommends inserting a 4.7 kΩ series resistor between the RST output and the MCU reset I/O, as shown in Figure 14 of the datasheet - this limits current during simultaneous drive and maintains signal integrity.

What is the maximum allowable load capacitance on the WDI pin when disabled?

When WDI is left unconnected or tristated, the maximum allowable load capacitance is 200 pF, and the maximum allowable leakage current is 10 µA, per Section 2.4 of the datasheet. Exceeding these values may prevent reliable automatic watchdog servicing and cause spurious resets.