STMicroelectronics STM809LWX6F

Overview

STM809LWX6F from STMicroelectronics is a precision low-power active-low reset supervisor IC for 3 V and 5 V microprocessor systems, featuring a 4.63 V ±3% reset threshold (25 °C), 140 ms minimum reset pulse width, 6 µA typical supply current, and guaranteed RST assertion down to VCC = 1.0 V. It monitors VCC in industrial-grade embedded controllers, power management units, and battery-backed systems where reliable power-on and brownout reset is critical.

For engineers reviewing the STM809LWX6F datasheet, STM809LWX6F pinout, STM809LWX6F application, or STM809LWX6F equivalent, key selection criteria include reset threshold accuracy over temperature (±0.25 V across –40 °C to 85 °C), SOT23-3 package compatibility, push-pull RST output drive capability (3.2 mA sink at VRST min), and immunity to sub-20 µs/100 mV VCC transients without false triggering.

Technical Context

The STM809LWX6F implements a precision voltage comparator with internal hysteresis and a monostable timer to generate a clean, debounced reset pulse. Its reset assertion is triggered when VCC falls below the 4.63 V nominal threshold, and the RST output remains low for ≥140 ms after VCC rises above threshold - ensuring MCU core and peripherals stabilize before release.

No manual reset input (MR) is present; this is a dedicated active-low reset device with fixed threshold and no external adjustment. The push-pull RST output drives directly into MCU reset pins without pull-up resistors and remains valid down to VCC = 1.0 V, enabling robust operation during gradual power decay.

Key Specifications

Pinout & Package

SOT23-3 package: ultra-compact 3-pin surface-mount outline (2.8 mm × 2.1 mm × 1.0 mm), lead-free ECOPACK® compliant, optimized for high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar reset supervisor applications.

Compared with MAX809LUR+T and TPS3809K33DBVR, the STM809LWX6F uniquely combines precise 4.63 V detection, guaranteed 1.0 V operation, and push-pull RST in SOT23-3 - making it optimal for legacy 5 V MCU designs requiring minimal BOM change and maximum reliability under marginal supply conditions.

Availability

STM809LWX6F is available at Aetrix Electronics and suitable for industrial automation, smart metering, and medical handheld devices requiring stable component supply and long-term lifecycle support.

Supply support for STM809LWX6F 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, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The STM809 series belongs to ST's precision reset supervisor product line, engineered specifically for deterministic power-on and brownout reset in resource-constrained embedded systems with strict reliability and footprint requirements.

FAQ

What is the exact reset threshold voltage of STM809LWX6F at 25 °C?

The STM809LWX6F has a nominal reset threshold of 4.63 V at 25 °C, with a guaranteed range of 4.56 V to 4.70 V per datasheet Table 5. This value is factory-trimmed and specified under standard test conditions (VCC = 5 V, TA = 25 °C), and shifts by ±0.25 V maximum across the full –40 °C to +85 °C operating range.

Does STM809LWX6F support manual reset functionality?

No, STM809LWX6F does not include a manual reset (MR) input. It is a dedicated active-low reset supervisor with only VCC monitoring. Manual reset capability is available only in the STM811 and STM812 variants (SOT143-4 package), which feature a fourth MR pin with internal 20 kΩ pull-up.

Can STM809LWX6F drive an ARM Cortex-M0+ reset pin directly?

Yes - its push-pull RST output sinks up to 3.2 mA at VRST(min) and sources current when deasserted, eliminating the need for an external pull-up resistor. It meets standard CMOS reset input requirements (VIH ≥ 0.7×VDD, VIL ≤ 0.3×VDD) for Cortex-M0+ MCUs operating at 3.3 V or 5 V, provided VCC remains ≥1.0 V during assertion.

Is STM809LWX6F RoHS and REACH compliant?

Yes, STM809LWX6F is supplied in an ECOPACK®-compliant SOT23-3 package, meeting RoHS Directive 2011/65/EU and REACH Regulation (EC) No. 1907/2006. The "F" suffix in the part number explicitly denotes lead-free, halogen-free, and green packaging per ST's environmental specifications.