STMicroelectronics STM6321SWY6F

Overview

STM6321SWY6F 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 open-drain RST for ≥1.4 ms, features 1.6 s watchdog timeout, and operates down to VCC = 1.0 V - used in industrial microcontroller power-up sequencing and fault recovery circuits.

For engineers reviewing the STM6321SWY6F datasheet, STM6321SWY6F pinout, STM6321SWY6F application, or STM6321SWY6F equivalent, key selection criteria include reset threshold accuracy, open-drain RST drive capability, watchdog timeout tolerance, MR input pull-up value, and SOT23-5 thermal performance across –40 to +85 °C.

Technical Context

The STM6321SWY6F implements a precision bandgap reference and comparator to detect VCC undervoltage conditions below 3.3 V ±2.5%. Its watchdog timer resets on WDI inactivity exceeding 1.6 s (typ.), cleared by any edge transition - supporting fail-safe MCU supervision without external timing components.

It provides an active-low open-drain RST output requiring external pull-up, plus an MR input with internal 52 kΩ pull-up enabling direct push-button connection. Reset assertion is guaranteed valid down to VCC = 1.0 V, and supply current remains ≤12 µA (typ.) at VCC < 3.6 V.

Key Specifications

Pinout & Package

STM6321SWY6F is housed in a standard 5-pin SOT23-5 package (JEDEC MO-178AB), with 1.3 mm height, 2.9 mm × 1.6 mm footprint, and lead-free RoHS-compliant construction.

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, STM6321SWY6F uniquely combines open-drain RST, integrated MR pull-up, and watchdog timer in one SOT23-5 package - reducing bill-of-materials and enabling compact, self-contained reset architecture.

Availability

STM6321SWY6F is available at Aetrix Electronics and suitable for industrial PLC controllers, medical sensor nodes, automotive body control modules, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM6321SWY6F 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 applications with emphasis on reliability and longevity.

STM632x belongs to ST's precision supervisor product line, engineered specifically for robust microprocessor reset management in harsh environments where voltage stability, watchdog safety, and minimal external components are critical.

FAQ

What is the exact reset threshold voltage and tolerance for STM6321SWY6F?

The STM6321SWY6F has a nominal reset threshold of 3.3 V with ±2.5% tolerance over temperature (–40 to +85 °C) and supply voltage (1.0 to 5.5 V). This is verified per Table 6 of DocID11110 Rev 14, where VTH is specified as 3.218 V (min) to 3.382 V (max) at TA = 25 °C and VCC = 3.3 V.

Can the watchdog function be disabled, and how?

Yes - the watchdog function is disabled when the WDI pin is left floating or driven by a tristate buffer. Per Section 1.1.4 and 2.4 of the datasheet, floating WDI causes the internal counter to generate a low-high-low pulse within the timeout period, preventing reset assertion. Maximum leakage (<10 µA) and capacitance (<200 pF) must be observed.

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

A 10 kΩ pull-up resistor to the target reset rail (up to 6 V) is recommended, as confirmed in Section 2.2 and Figure 11. This value ensures logic-low recognition under worst-case sink current (20 mA max) while minimizing power draw and noise susceptibility in typical industrial layouts.

Does STM6321SWY6F support operation below 3.3 V supply, and down to what level?

Yes - the device operates from VCC = 1.0 V to 5.5 V (Table 5), and guarantees valid RST assertion down to VCC = 1.0 V across full temperature range. This is explicitly stated in Section 2.1 and validated in Figure 15, enabling use in brownout recovery and backup power scenarios.