STMicroelectronics STM708AM6F

Overview

STM708AM6F from STMicroelectronics is a 5 V precision voltage supervisor IC with dual reset outputs (active-low RST and active-high RST), power-fail comparator (PFI/PFO), manual reset input (MR), and no watchdog timer. It asserts reset down to VCC = 1.0 V, features 4.25–4.50 V reset threshold, 200 ms typical reset timeout (trec), and operates from –40 °C to 85 °C in industrial applications such as microcontroller-based embedded control systems.

For engineers reviewing the STM708AM6F datasheet, STM708AM6F pinout, STM708AM6F application, or STM708AM6F equivalent, key selection considerations include its dual-reset output polarity, absence of watchdog functionality (distinguishing it from STM705/706), PFI threshold of 1.25 V ±1%, guaranteed reset assertion at low VCC, and TSSOP8 package compatibility with space-constrained PCB layouts.

Technical Context

The STM708 is a dedicated supervisor IC without integrated watchdog logic-unlike STM705/706/813L-making it suitable for systems where external watchdog management is preferred or unnecessary. Its dual reset outputs (RST and RST) provide flexible interface options for MCUs requiring either active-low or active-high reset signaling.

It employs a precision bandgap reference and comparator to monitor VCC against a fixed 4.25–4.50 V threshold, with reset assertion guaranteed down to VCC = 1.0 V. The power-fail comparator uses an independent 1.25 V reference (VPFI), enabling early warning of supply decay before VCC crosses the main reset threshold.

Key Specifications

Pinout & Package

STM708AM6F is housed in an 8-pin TSSOP package (3 mm × 3 mm body, 0.65 mm pitch), optimized for high-density PCB layouts. Pin assignments are validated per STMicroelectronics DocID10520 Rev 11 (Figures 5–6 and Table 3).

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM706M6F, STM708AM6F removes watchdog overhead for deterministic reset-only operation; versus MAX809SEUR+T, it adds critical PFI/PFO and dual-reset flexibility essential for robust system-level power management.

Availability

STM708AM6F is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, automotive body control modules, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM708AM6F 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/mixed-signal ICs, with strong focus on industrial, automotive, and IoT applications.

The STM70x series is designed specifically for reliable microprocessor supervision in mission-critical embedded systems, emphasizing precision voltage monitoring, low-power operation, and robust reset timing under varying supply conditions.

FAQ

What is the function of the NC pin on STM708AM6F?

Pin 3 is a no-connect (NC) terminal with no internal bond wire or circuit connection. It must remain unconnected on the PCB - neither routed nor terminated - to avoid unintended coupling or mechanical stress on the die. This pin exists solely for package symmetry and manufacturing compatibility with other members of the STM70x family.

Can STM708AM6F be used with a 3.3 V microcontroller?

STM708AM6F is specified for 5 V operation only (VCC = 4.5–5.5 V) and its reset thresholds and output drive levels are calibrated for that rail. While RST/RST outputs may interface with 3.3 V-tolerant MCU inputs, the device itself cannot be powered from 3.3 V. For 3.3 V systems, ST recommends the STM3405 or similar 3.3 V supervisors.

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

The PFI/PFO comparator operates independently of the VCC monitor - it uses a separate 1.25 V reference and triggers PFO low when PFI falls below VPFI. This allows early warning of supply decay (e.g., via resistor divider on unregulated input) up to tens of milliseconds before VCC crosses the 4.25–4.50 V reset threshold, enabling graceful shutdown or data save operations.

Is external capacitor required on the MR pin for noise immunity?

A 0.1 µF capacitor from MR to GND is recommended only in electrically noisy environments or when MR is driven via long cables. The pin includes an internal pull-up, and for typical PCB layouts with short traces, no external capacitor is needed - the built-in trec timer inherently debounces switch bounce without additional components.