STMicroelectronics STM6822LWY6F

STM6822LWY6F Microprocessor Supervisor Product Summary

The STM6822LWY6F, designed by STMicroelectronics, is a single-channel supervisor IC with integrated watchdog timer and push-button reset input, assembled in a compact SOT23-5 package. Targeted at applications requiring robust system monitoring and manual or automatic reset functionality, the STM6822LWY6F supervises microprocessor supply voltage rails, ensuring system reliability by providing precise undervoltage detection and reset signaling. The device operates over a wide temperature range of –40°C to +85°C and supports various supply voltage thresholds (5V, 3.3V, 3V, or 2.5V), granting flexibility for contemporary and legacy designs.

Main Features of STM6822LWY6F

The STM6822LWY6F offers a precise suite of features intended to address the needs of embedded and industrial systems:

Precision VCC monitoring for 5V, 3.3V, 3.0V, or 2.5V power supply rails.

Open drain, active-low reset output (RST), ideal for interfacing with a range of microcontrollers and logic devices; requires an external pull-up resistor to the system supply.

Multiple reset pulse widths: 1.4 ms, 200 ms, or 240 ms (typical), supporting various timing needs.

Watchdog timer with a typical 1.6 s timeout, ensuring proper system operation and detecting microprocessor faults.

Manual reset input (MR), allowing assertion of system reset via a push-button or external logic.

Reliable reset assertion guaranteed down to VCC = 1.0V, ensuring correct system behavior during supply transients.

Industry-standard operating temperature range (–40°C to +85°C) and RoHS-compliant, lead-free construction.

Minimal supply current (typically 3 µA), suiting battery-powered and low-power applications.

STM6822LWY6F Block Diagram and Pinout Description

The STM6822LWY6F is housed in a 5-pin SOT23-5 package, whose small footprint is conducive to dense PCB layouts. The pinout enables straightforward integration:

VCC: Power supply input, monitored by the internal precision reference and comparator.

GND: Ground reference.

RST (open drain): Active low reset output, can be wired to various system voltages through a suitable pull-up resistor.

MR: Manual reset input, with internal pull-up for direct push-button or logic drive.

WDI: Watchdog input; expects periodic toggling from the supervised microcontroller to prevent unwanted resets.

On the block level, the STM6822LWY6F combines a window comparator (for voltage detection), a watchdog timer logic block, and a manual reset monitoring circuit. The reset output is driven based on threshold crossings, watchdog timeouts, or manual reset activations, enabling comprehensive system oversight.

STM6822LWY6F Operating Principles

The STM6822LWY6F monitors the supply voltage (VCC) through a high-precision internal reference. When VCC falls below the predefined voltage threshold, the open-drain RST output is asserted low, compelling the microprocessor to enter a reset state. This is particularly vital during power-up, brownout, or power-down events, preventing unpredictable system behavior.

On power-up, the device holds RST low for the selected reset timeout period (t_rec) after VCC surpasses the threshold, ensuring stable initialization. The open-drain output configuration allows flexible pull-up to different logic levels and easy integration with multiple supply rails.

A key addition is the watchdog timer feature. The monitored microcontroller or processor must regularly toggle the WDI pin; failure to do so within the 1.6 s window triggers a reset pulse, catching firmware lockup or code runaways. This function enhances overall system resilience against software faults.

The manual reset input (MR) allows an external push-button or logic signal to force a system reset, adding an essential layer of serviceability and end-user control. An internal pull-up resistor on MR allows for direct wiring to ground via switch or logic, while immunity to noise can be enhanced using an external capacitor.

Design and Application Guidelines for STM6822LWY6F

Integrating the STM6822LWY6F into a system involves several design choices:

The open-drain RST output must be tied via a pull-up resistor to the appropriate system voltage (up to 6 V); a common value is 10 kΩ, balancing output current sink capability and rise time.

When connecting to microprocessor reset lines that are bidirectional, it is recommended to use a series resistor (typically 4.7 kΩ) between the supervisor and processor to prevent unwanted contention.

For the watchdog function, the WDI input should be periodically toggled by the processor. If the watchdog is intentionally disabled, WDI can be left unconnected or tied to a tristated output, provided the line’s leakage and capacitance constraints are met.

The manual reset input MR can be connected to a momentary switch for user-initiated resets. If deployed in a noisy or long-line environment, a 0.1 µF capacitor from MR to ground provides additional robustness.

If valid reset signaling is required down to VCC = 0 V (such as power-loss detection), certain additional resistors may be employed for push-pull output versions, but this does not apply to the open-drain output of the STM6822LWY6F.

Standard Operating Characteristics of STM6822LWY6F

Key electrical and timing parameters to consider include:

Minimal supply current: Typically 3 µA, benefiting low-power operations.

Reset output delay responds predictably across the full operating temperature range.

Reset threshold voltage and watchdog timeout maintain tight tolerances under temperature variation, supporting reliable system startup and runtime behavior.

Output driving characteristics: The RST pin’s voltage-low and voltage-high behaviors versus sinking and sourcing current are well-characterized.

These parameters are essential for engineers tasked with detailed system timing analysis and power budget calculations.

STM6822LWY6F Absolute Maximum Ratings and Reliability Information

The STM6822LWY6F supports standard industrial qualification:

Absolute maximum ratings ensure the device can safely withstand stresses such as brief overvoltage or soldering reflow (peak up to 260°C, within thermal budget).

The part operates across the full –40°C to +85°C range without derating.

RoHS compliance guarantees use in green designs.

It is imperative that applications do not exceed the listed absolute maximums in voltage, temperature, or input/output pin conditions to preserve long-term reliability.

STM6822LWY6F DC and AC Electrical Specifications

The DC and AC characteristics determine the suitability for specific applications:

VCC operating ranges are determined by the device option (for STM6822LWY6F, typically 4.5–5.5V or 2.7–3.6V, depending on suffix).

Reset threshold accuracy, reset and watchdog timing, input/output logic levels, and leakage currents are all tightly specified.

The device guarantees operation down to 1.0 V VCC and is electrically characterized for all logic transitions, propagation delays, and watchdog behaviors.

These values support precise interface compatibility and enable deterministic MCU/system startup and recovery.

STM6822LWY6F Package Details and Mechanical Drawings

The SOT23-5 package of the STM6822LWY6F is optimized for compactness without sacrificing reliability:

Small outline and low profile allow efficient use in crowded PCB layouts.

Mechanically, the package supports standard automated assembly and is compliant with ECOPACK® environmental guidelines.

Detailed outline and carrier tape dimensions are available for manufacturing process design.

Alternative or Substitute Models for STM6822LWY6F

For designs requiring alternatives or considering dual-sourcing, related devices within the STM632x/STM682x supervisor family should be evaluated:

STM6321, STM6322: Offer similar voltage supervision and watchdog functions, with variations in output type (open drain/push-pull) and configuration.

STM6821, STM6823, STM6824, STM6825: Provide further combinations of output signal polarity and configuration. Selection depends on desired reset output and watchdog feature set.

When migrating between models, it is essential to verify pinout, operating voltage range, reset timeout periods, and watchdog timer settings to ensure compatibility. Designers may also consider other industry-standard SOT23-5 supervisors for suitable electrical and feature matches, evaluating parameters like reset output structure, watchdog timer availability, and manual reset integration.

Conclusion

The STM6822LWY6F from STMicroelectronics brings together precise voltage supervision, a configurable watchdog function, and manual reset capability in a compact SOT23-5 package. Its design addresses the need for reliable system startup, fail-safe operation, and recovery from software or power anomalies in embedded and industrial applications. With low supply current, enhanced flexibility, and robust qualification, it stands as a compelling solution for product selection engineers and procurement personnel seeking to safeguard microprocessor-based systems. When integrating the STM6822LWY6F, careful review of system timing, voltage compatibility, and board-level layout ensures a resilient and maintainable application design. For drop-in replacements or functionally similar supervisors, the broader STMicroelectronics STM632x/STM682x family provides an array of alternatives compatible with diverse system architectures.