STMicroelectronics STM708RM6E

Overview

STM708RM6E from STMicroelectronics is a 3 V precision voltage supervisor IC with dual active-low and active-high reset outputs, 200 ms reset timeout, power-fail comparator (PFI/PFO), and industrial-grade operation (–40 °C to +85 °C). It monitors VCC for out-of-tolerance conditions, asserts RST/RST on undervoltage or manual reset, and provides early power-fail warning for microprocessor-based systems in embedded controllers and instrumentation.

For engineers reviewing the STM708RM6E datasheet, STM708RM6E pinout, STM708RM6E application, or STM708RM6E equivalent, key selection criteria include reset threshold accuracy (2.88 V ≤ VRST ≤ 3.00 V for 'S' variant), guaranteed RST assertion down to VCC = 1.0 V, push-pull PFO output, MR input with internal 40 kΩ pull-up, and TSSOP8 package compatibility with space-constrained PCB layouts.

Technical Context

The STM708RM6E implements a precision bandgap reference and dual comparators: one for VCC monitoring (VRST = 2.88–3.00 V) and another for independent power-fail detection (VPFI ≈ 1.25 V). Its logic diagram shows separate RST (active-low) and RST (active-high) outputs driven by the same reset generator, enabling simultaneous interface with mixed-logic microcontrollers.

Unlike STM706 variants, the STM708RM6E omits the watchdog timer (no WDI/WDO pins), simplifying supervision for systems requiring only voltage monitoring and manual/power-fail reset control. The PFO output is push-pull and designed to drive MR directly, while MR features internal pull-up and noise immunity support via optional 0.1 µF capacitor to ground.

Key Specifications

Pinout & Package

STM708RM6E is housed in an 8-pin TSSOP package (3 mm × 3 mm body, 0.65 mm lead pitch) with exposed pad for thermal performance. Pin numbering follows standard JEDEC TSSOP convention (pin 1 top-left, counterclockwise).

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM708RM6E, STM708SM6E offers higher reset threshold for improved noise immunity on clean 3.0 V rails, while TPS3808G33DBVR trades dual-reset and power-fail functions for ultra-low IQ and minimal footprint-making it viable only when those features are omitted from system requirements.

Availability

STM708RM6E is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, smart energy meters, and automotive body control modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for STM708RM6E 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The STM70x series is ST's dedicated family of precision voltage supervisors targeting microprocessor reset assurance in harsh environments, emphasizing threshold accuracy, low IQ, and dual-output flexibility for heterogeneous system architectures.

FAQ

What is the function of the NC pin on STM708RM6E?

Pin 8 is a no-connect (NC) terminal with no internal bond wire or circuit connection. It must remain electrically floating-neither tied to VCC, VSS, nor routed on PCB-to prevent parasitic coupling or mechanical stress on the die. This pin exists solely for mechanical symmetry in the TSSOP8 package.

Can PFO be used to drive an external LED indicator?

Yes-PFO is a push-pull output capable of sinking up to 20 mA. A current-limiting resistor (e.g., 1 kΩ for ~2 mA at 3 V) can connect PFO to an LED anode with cathode to VSS. This provides visual indication of power-fail condition without loading the comparator or affecting reset timing.

How does STM708RM6E differ from STM706R in functionality?

STM708RM6E lacks the watchdog timer (no WDI/WDO pins) present in STM706R, simplifying supervision for systems that do not require software-alive monitoring. It retains identical RST/RST dual outputs, PFI/PFO, MR, and 200 ms trec-but removes watchdog-related timing constraints and pin count.

Is the MR input compatible with 5 V logic signals?

No-MR is strictly a 3 V domain input with absolute maximum rating of VCC + 0.3 V. Driving it with 5 V logic risks latch-up or permanent damage. Interface via a resistive divider (e.g., 10 kΩ + 15 kΩ) or level-shifter IC if upstream logic operates at 5 V.