STMicroelectronics STM708M6F

Overview

STM708M6F from STMicroelectronics is an industrial-grade 5 V microprocessor supervisory IC with dual active-low reset outputs (RST and RST), precision V_CC monitoring at 4.25–4.50 V, 200 ms reset timeout (t_rec), power-fail comparator (PFI/PFO), and manual reset input (MR). It ensures reliable system initialization and fault recovery in embedded controllers, PLCs, and industrial power supplies.

For engineers reviewing the STM708M6F datasheet, STM708M6F pinout, STM708M6F application, or STM708M6F equivalent, key selection criteria include its guaranteed RST assertion down to V_CC = 1.0 V, push-pull output drive capability, TSSOP8 package footprint, and absence of watchdog functionality-distinguishing it from STM705/706/813L variants.

Technical Context

The STM708M6F implements a dual-comparator architecture: one for V_CC supervision (4.25–4.50 V threshold) and another for independent power-fail detection (VPFI ≈ 1.25 V). It asserts both RST and RST simultaneously on V_CC undervoltage or MR low, with t_rec = 200 ms (typ) ensuring stable MCU release after power stabilization.

No watchdog timer is integrated-unlike STM705/706/813L-making it suitable for systems where external supervision or software-based watchdogs are preferred. Its PFO output provides early warning of supply decay via externally scaled PFI voltage, supporting fail-safe shutdown sequencing in 5 V rail systems.

Key Specifications

Pinout & Package

STM708M6F is housed in an 8-pin TSSOP package (3 mm × 3 mm body, 0.65 mm pitch), optimized for space-constrained industrial PCBs. Pin assignments are validated per ST's DocID10520 Rev 11 (Figures 6 and Table 3).

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM706M6F, STM708M6F trades watchdog capability for simpler layout and reduced BOM count; versus MAX809SEUR+T, it delivers dual-reset polarity, power-fail warning, and manual reset-all in the same TSSOP8 footprint-without sacrificing industrial temperature range or low-current operation.

Availability

STM708M6F is available at Aetrix Electronics and suitable for industrial PLCs, smart energy meters, factory automation controllers, and medical diagnostic equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM708M6F 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 specializing in microcontrollers, power management, and analog ICs, with strong focus on industrial, automotive, and embedded markets.

The STM70x series is designed specifically for robust, low-power microprocessor supervision in harsh industrial environments-emphasizing precision threshold accuracy, guaranteed low-voltage reset assertion, and flexible reset signaling.

FAQ

What is the function of the NC pin on STM708M6F?

Pin 3 is designated NC (No Connect) and is internally unconnected. It must remain un-routed and un-soldered on the PCB. Connecting or loading this pin may cause unpredictable behavior or damage due to internal floating node exposure. ST confirms no internal circuitry links to this terminal in any revision of the device.

Can STM708M6F be used with a 3.3 V microcontroller?

No-STM708M6F is specified only for 5 V operation (4.5–5.5 V V_CC). Its reset thresholds, output drive levels, and internal references are calibrated for 5 V systems. Using it with 3.3 V logic risks incorrect reset assertion, insufficient noise margin, and potential damage if V_CC falls outside absolute maximum ratings. For 3.3 V systems, consider STM32Fxx-integrated reset or dedicated 3.3 V supervisors like STM809.

How does the power-fail comparator interact with the main reset function?

The PFI/PFO comparator operates independently of the V_CC reset circuit: VPFI ≈ 1.25 V is fixed and unrelated to V_RST. When PFI drops below VPFI, PFO goes low-but this does not trigger RST unless externally wired (e.g., PFO → MR). This decoupling allows staged response: PFO can initiate graceful shutdown (e.g., saving state), while RST enforces hard reset only when V_CC itself fails.

Is there a recommended external capacitor for MR debounce?

No external capacitor is required. The MR input features an internal 40 kΩ pull-up and is designed for direct switch-to-ground connection with inherent noise immunity. ST explicitly states that external debounce circuitry is unnecessary-only a 0.1 µF capacitor to ground is advised *only* in exceptionally noisy environments or with >10 cm cable runs. Adding capacitance unnecessarily increases MR response latency and may violate t_rec-based timing margins.