STMicroelectronics STM6321TWY6F

Overview

STM6321TWY6F 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 PLCs, IoT edge nodes, and battery-backed MCU systems.

For engineers reviewing the STM6321TWY6F datasheet, STM6321TWY6F pinout, STM6321TWY6F application, or STM6321TWY6F equivalent, key selection criteria include reset threshold accuracy, open-drain RST drive capability, MR input pull-up value, watchdog disable behavior, and guaranteed operation below 1.2 V supply.

Technical Context

The STM6321TWY6F implements a precision bandgap reference and comparator to monitor VCC against a fixed 3.3 V threshold (±2.5% over –40°C to +85°C). Its reset logic asserts RST low when VCC drops below threshold, on MR low assertion, or after 1.6 s WDI inactivity - with trec = 1.4 ms (typ.) reset pulse width.

It uses an open-drain RST output requiring external pull-up (up to 6 V), supports manual reset via internal 52 kΩ MR pull-up, and allows watchdog disable by floating WDI - all within 3 µA (typ.) quiescent current and full industrial temperature range.

Key Specifications

Pinout & Package

STM6321TWY6F is housed in a standard SOT23-5 surface-mount package (2.9 mm × 1.6 mm, 0.95 mm height), optimized for space-constrained PCB layouts in portable and industrial electronics.

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, STM6321TWY6F uniquely combines open-drain RST, integrated MR pull-up, and functional watchdog in a single SOT23-5 package - making it optimal for cost-sensitive, space-constrained designs requiring both manual and autonomous reset assurance.

Availability

STM6321TWY6F is available at Aetrix Electronics and suitable for industrial PLCs, smart energy meters, wireless sensor nodes, and medical handheld devices requiring stable component supply across extended product lifecycles.

Supply support for STM6321TWY6F 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 consumer markets since 1987.

STM6321TWY6F belongs to the STM6xxx supervisor family, engineered specifically for robust, low-power microprocessor reset management in harsh industrial and battery-operated environments.

FAQ

What is the exact reset threshold voltage for STM6321TWY6F?

The STM6321TWY6F has a nominal VCC reset threshold of 3.3 V with ±2.5% tolerance over –40°C to +85°C. This corresponds to 3.218 V (min) to 3.383 V (max) at 25°C, verified per Table 6 of DocID11110 Rev 14. The threshold remains stable across temperature with ±0.03%/°C drift.

Can the watchdog timer be disabled, and how?

Yes - the watchdog function is disabled when the WDI pin is left unconnected (floating) or driven by a tristate buffer. In this state, internal leakage (<10 µA) and load capacitance (<200 pF) must remain within limits. No configuration register or external signal is required; it is a hardware-level disable.

Is an external pull-up resistor required for the RST output?

Yes - because STM6321TWY6F features an active-low open-drain RST output, a pull-up resistor to any supply ≤6 V is mandatory. A 10 kΩ resistor is recommended for most applications; values from 4.7 kΩ to 100 kΩ are acceptable depending on bus capacitance and rise-time requirements.

Does STM6321TWY6F support bidirectional MCU reset pins?

Yes - when interfacing with microprocessors having bidirectional reset I/O (e.g., some STM32 and NXP Kinetis devices), a 4.7 kΩ series resistor between RST and the MCU pin prevents contention. This matches the recommendation in Figure 14 of the datasheet and avoids simultaneous drive conflicts.