STMicroelectronics STM706SM6E

Overview

STM706SM6E from STMicroelectronics is a precision 3 V supply voltage supervisor IC with active-low reset output, integrated watchdog timer (1.6 s timeout), power-fail comparator (VPFI = 1.25 V), and manual reset input. It guarantees RST assertion down to VCC = 1.0 V and operates from –40 °C to +85 °C in industrial environments. Used for reliable power-on reset and fault recovery in microcontroller-based embedded systems.

For engineers reviewing the STM706SM6E datasheet, STM706SM6E pinout, STM706SM6E application, or STM706SM6E equivalent, key selection criteria include reset threshold tolerance (±2.5% for T-grade), trec = 200 ms typical, low 40 µA quiescent current, push-pull RST/RST outputs, and compatibility with bi-directional MCU reset pins via series resistor.

Technical Context

The STM706SM6E implements a dual-comparator architecture: one monitors VCC against a precision bandgap reference (VRST = 3.00–3.15 V) to assert RST during undervoltage, while a second compares PFI against a separate 1.25 V reference to generate early power-fail warning via PFO. Its internal 200 ms reset timeout timer ensures clean MCU initialization after power-up or MR assertion.

It integrates a 1.6 s watchdog timer that clears on any WDI edge (≥50 ns pulse width), with WDO asserted only when timeout occurs - not automatically tied to RST unless externally connected to MR. All outputs (RST, WDO, PFO) are push-pull, enabling direct interface to TTL/CMOS logic without external pull-ups.

Key Specifications

Pinout & Package

STM706SM6E is housed in an 8-pin SOIC (SO8) package with 150 mil body width, RoHS-compliant lead-free finish, and standard JEDEC MS-012AC footprint. Pin pitch is 1.27 mm; package dimensions are 4.9 × 3.9 × 1.75 mm (L × W × H).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361KA29+T and TPS3808G33DBVR, STM706SM6E uniquely integrates three critical supervisory functions - precision VCC reset, predictive power-fail detection, and configurable watchdog - in a single SO8 package without external components, reducing board area and qualification effort for industrial and medical designs.

Availability

STM706SM6E is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, smart energy meters, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM706SM6E 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 family was developed specifically for robust microprocessor supervision in harsh industrial and medical environments, emphasizing guaranteed reset behavior over wide voltage and temperature ranges without software dependency.

FAQ

What is the exact reset threshold voltage for STM706SM6E?

The STM706SM6E is the 'T' grade variant, with a guaranteed reset threshold (VRST) of 3.00 V to 3.15 V at 25 °C. This tolerance (±2.5%) is specified over the full –40 °C to +85 °C operating range and ensures reliable reset assertion before most 3.3 V MCUs enter brownout. The threshold is set by internal laser-trimmed resistors and does not require external calibration.

Can the watchdog timer be disabled without modifying hardware?

Yes - the watchdog timer is automatically disabled when the WDI pin is left floating or driven to high-impedance (tri-stated). ST specifies maximum leakage current ≤10 µA and load capacitance ≤200 pF under this condition. No register write, strap pin, or external jumper is needed; this behavior is inherent to the analog watchdog circuit design.

How does the power-fail comparator differ from the VCC reset comparator?

The PFI comparator uses a dedicated 1.25 V ±1.2% internal reference, independent from the 3.08 V VCC reset reference. It allows early detection of supply collapse by monitoring an unregulated rail (e.g., 12 V input) via external resistor divider, triggering PFO before VCC drops below its reset threshold - providing up to 100 ms warning margin for controlled shutdown.

Is STM706SM6E compatible with MCUs that have bidirectional reset pins?

Yes - ST explicitly recommends adding a 4.7 kΩ series resistor between RST and the MCU's bidirectional reset I/O to prevent contention. This isolates the STM706SM6E's push-pull RST driver from the MCU's internal pull-up/down, allowing safe reset assertion and release without risk of latch-up or excessive current draw during state transitions.