STMicroelectronics STM805LM6F

Overview

STM805LM6F from STMicroelectronics is a 5 V microprocessor supervisory IC with battery switchover, active-high reset output (RST), watchdog timer (1.6 s typ), and power-fail comparator (PFI/PFO). It monitors VCC for out-of-tolerance conditions, asserts reset down to VCC = 1.0 V, and provides non-volatile SRAM backup via VOUT switching between VCC and VBAT. Used in industrial embedded systems requiring reliable power monitoring and data retention during brownouts.

For engineers reviewing the STM805LM6F datasheet, STM805LM6F pinout, STM805LM6F application, or STM805LM6F equivalent, key selection criteria include guaranteed RST assertion at low VCC, automatic battery switchover behavior, watchdog timeout accuracy, and push-pull reset output drive capability in SO8 package.

Technical Context

The STM805LM6F implements a precision voltage reference and comparator to monitor VCC against a fixed reset threshold (VRST ≈ 4.63 V), triggering RST assertion when VCC falls below VRST or after manual reset (MR) or watchdog timeout. Its internal P-channel MOSFET switch enables seamless VOUT switchover from VCC to VBAT when VCC drops below the lesser of VBAT and VRST, supporting external LPSRAM backup without external circuitry.

It features dual reset outputs (RST active-high, no RST active-low), a 1.6 s typical watchdog timer cleared by WDI edge transitions, and a push-pull PFO output that asserts low on power-fail detection (VPFI = 2.4 V nominal). All I/Os are TTL/CMOS-compatible with internal pull-ups on MR and defined logic states in battery-backup mode.

Key Specifications

Pinout & Package

STM805LM6F is housed in an 8-pin SO8 (Small Outline) package per JEDEC MS-012, with 1.27 mm pitch and surface-mount footprint. Pin 1 is marked with a dot or bevelled corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervision applications.

Compared with MAX809SEUR+T and TPS3823MPW, STM805LM6F uniquely integrates battery switchover, dual reset outputs, and power-fail signaling in one SO8 device - eliminating four external components typically needed for equivalent functionality in industrial data retention designs.

Availability

STM805LM6F is available at Aetrix Electronics and suitable for industrial PLC controllers, medical data loggers, smart energy meters, and automotive telematics units requiring stable component supply with long-term lifecycle support.

Supply support for STM805LM6F 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 STM805LM6F belongs to ST's legacy supervisor product line targeting robust, low-power microprocessor monitoring in harsh environments - optimized for reliability over extended temperature ranges and minimal external component count.

FAQ

What is the reset threshold voltage and tolerance for STM805LM6F?

The STM805LM6F has a nominal reset threshold of 4.63 V with ±2.5% tolerance over temperature (–40 °C to +85 °C), ensuring RST assertion begins before critical MCU operation fails. This value is factory-trimmed and specified in Table 7 of DocID10522 Rev 11, with guaranteed assertion down to VCC = 1.0 V regardless of VBAT status.

Does STM805LM6F support both VCC and VBAT powering of external LPSRAM simultaneously?

No. STM805LM6F uses a single-pole, double-throw (SPDT) internal P-channel MOSFET switch to connect VOUT exclusively to either VCC or VBAT - never both. When VCC ≥ VSO (min(VBAT, VRST)), VOUT is sourced from VCC; when VCC falls below VSO, VOUT switches to VBAT with <100 Ω on-resistance, preventing backfeed or contention.

Can the watchdog timer be disabled, and how?

Yes. The watchdog timer is disabled when the WDI pin is left floating or tri-stated, provided leakage current stays below 10 µA and load capacitance remains under 200 pF. Driving WDI continuously high or low will cause periodic resets every ~1.8 s (tWD + trec), so disconnection - not static logic - is the intended disable method.

Is STM805LM6F RoHS compliant and lead-free?

Yes. STM805LM6F is fully RoHS compliant and manufactured with lead-free terminations per Directive 2011/65/EU. The "M6F" suffix in the part number denotes RoHS-compliant, halogen-free, and green packaging - confirmed in Table 9 (Ordering Information) and Section 8 (Revision History) of the official datasheet.