STMicroelectronics STM705M6F

Overview

STM705M6F from STMicroelectronics is a 5 V precision voltage supervisor IC with active-low RST, active-high RST, manual reset (MR), watchdog timer (WDI/WDO), and power-fail comparator (PFI/PFO). It asserts reset for VCC < 4.625 V (typ), provides 200 ms reset timeout (trec), delivers 1.6 s watchdog timeout, draws 40 µA supply current, and operates from –40 °C to 85 °C - used in industrial microcontroller power-up sequencing and brownout protection.

For engineers reviewing the STM705M6F datasheet, STM705M6F pinout, STM705M6F application, or STM705M6F equivalent, key selection criteria include reset threshold accuracy (±1.5% over temperature), guaranteed RST assertion down to VCC = 1.0 V, push-pull RST/RST outputs, MR debounced by internal pull-up, and compatibility with 5 V MCU reset interfaces requiring dual-polarity reset signaling.

Technical Context

The STM705M6F integrates a precision bandgap reference, dual comparators (VCC monitor and PFI threshold), trec timer, and watchdog state machine. Its reset logic combines VCC monitoring, MR edge detection, and WDO feedback path capability - enabling self-resetting behavior when WDO is tied to MR.

It features independent VPFI = 1.25 V (±1%) comparator with 1.5 µs propagation delay, RST output valid down to VCC = 1.0 V, and push-pull drivers capable of sinking 20 mA (RST) and sourcing 10 mA (RST) at VCC = 5 V - supporting direct interface to TTL/CMOS inputs without external buffers.

Key Specifications

Pinout & Package

STM705M6F is housed in an 8-pin TSSOP package (3 mm × 3 mm, 0.65 mm pitch), RoHS-compliant, with exposed pad not connected. Pin layout matches JEDEC MO-153, suitable for high-density PCB layouts and reflow assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692AESA+ and TPS3808G33DBVR, STM705M6F uniquely delivers 5 V operation with dual-polarity reset, integrated watchdog, and independent power-fail comparator - making it the only option among the three that satisfies full-featured industrial supervision without external components.

Availability

STM705M6F is available at Aetrix Electronics and suitable for industrial control systems, medical diagnostics equipment, automotive body electronics, and smart metering applications requiring stable component supply and long-term manufacturability.

Supply support for STM705M6F 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 microcontrollers, power management ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The STM70x series was developed specifically for robust, low-cost microprocessor supervision in space-constrained industrial and automotive applications - emphasizing precision threshold stability, guaranteed low-VCC reset behavior, and integrated fault-detection functions.

FAQ

Can STM705M6F be used with 3.3 V microcontrollers?

Yes - its RST and RST outputs are compatible with 3.3 V logic inputs when VCC = 5 V, as RST sinks 20 mA and RST sources 10 mA with VOL ≤ 0.4 V and VOH ≥ 4.5 V. However, the device itself requires 5 V supply and does not operate below 4.5 V, so it cannot supervise 3.3 V rails directly.

What happens if WDI is left unconnected?

Leaving WDI floating disables the watchdog function entirely, as the internal timer requires defined logic transitions to clear. No reset will occur due to watchdog timeout, and WDO remains high. This is a documented configuration for systems not requiring runtime firmware supervision.

How is the power-fail warning threshold set?

VPFI is fixed at 1.25 V (±1%). An external resistor divider from the monitored supply (e.g., unregulated input) to PFI sets the trip point - for example, a 100 kΩ/12.5 kΩ divider yields 1.25 V at PFI when input is 11.25 V, triggering PFO low ~10 ms before VCC drops below 4.5 V.

Does STM705M6F require external capacitors?

No external timing or bypass capacitors are required. The 200 ms trec is internally generated; VCC decoupling (0.1 µF ceramic) is recommended per standard practice but not mandated by the IC's operation. MR debouncing is handled internally via pull-up and logic filtering.