STMicroelectronics STM708RAM6F

Overview

STM708RAM6F 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), and manual reset input (MR). It asserts reset for VCC < 4.25 V (typ), guarantees RST assertion down to VCC = 1.0 V, and features 200 ms typical reset timeout (trec). Used in industrial microcontroller systems requiring reliable power-on and brownout detection.

For engineers reviewing the STM708RAM6F datasheet, STM708RAM6F pinout, STM708RAM6F application, or STM708RAM6F equivalent, key selection criteria include reset threshold accuracy (4.25–4.50 V), guaranteed low-VCC reset assertion, push-pull RST/RST output drive capability, PFI/PFO undervoltage warning functionality, and compatibility with noisy or long-cable MR interfaces.

Technical Context

The STM708 operates as a self-contained supervisory circuit with independent precision comparators for VCC monitoring (VRST = 4.25–4.50 V) and power-fail detection (VPFI ≈ 1.25 V). Its dual reset outputs are implemented as complementary push-pull drivers, enabling direct interface to both active-low and active-high MCU reset pins without external inversion.

No watchdog timer is integrated - unlike STM705/706/813L variants, the STM708 omits WDI/WDO functionality per its logic diagram and device summary. The MR input includes an internal 40 kΩ pull-up resistor and supports TTL/CMOS-compatible triggering with trec-based deassertion timing after release.

Key Specifications

Pinout & Package

STM708RAM6F is housed in an 8-pin TSSOP package (3 mm × 3 mm body, 0.65 mm pitch), RoHS-compliant and optimized for high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM706RM6F, STM708RAM6F removes watchdog circuitry to reduce cost and simplify design where software-level watchdogs suffice; versus MAX692CPA+, it adds PFI/PFO capability and modern TSSOP packaging while maintaining identical core reset reliability.

Availability

STM708RAM6F is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, smart metering, and automotive body electronics requiring stable component supply and long-term lifecycle support.

Supply support for STM708RAM6F 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 silicon solutions for automotive, industrial, and consumer markets.

The STM70x series is ST's dedicated family of precision voltage supervisors targeting robust power-monitoring in microcontroller-based systems, emphasizing low-power operation, guaranteed reset behavior, and flexible interface options.

FAQ

What is the function of the NC pin on STM708RAM6F?

Pin 3 is designated NC (No Connect) and is internally unconnected. It must remain unconnected on the PCB - no pull-up, pull-down, or routing is permitted. This pin exists solely for mechanical symmetry in the TSSOP-8 package and has no electrical function.

Can STM708RAM6F be used with a 3.3 V microcontroller?

STM708RAM6F is specified for 5 V operation only (VCC = 4.5–5.5 V). Its RST/RST outputs are 5 V-tolerant push-pull drivers, so direct connection to a 3.3 V MCU reset pin requires a level-shifter or voltage divider to avoid overvoltage damage. It does not support 3.3 V supply operation.

How does the power-fail comparator (PFI/PFO) interact with the reset outputs?

PFI/PFO operates independently of the VCC reset comparator. A low PFO signal indicates PFI < VPFI (≈1.25 V) but does not directly assert RST or RST. To trigger reset on power failure, PFO must be externally connected to MR. No internal coupling exists between PFO and reset logic.

Is the MR input compatible with open-drain microcontroller GPIOs?

Yes - the MR input has an internal 40 kΩ pull-up resistor and accepts logic-low signals down to 0.8 V. An open-drain GPIO can safely drive MR low without external components. For noise immunity in long-trace or high-EMI environments, a 0.1 µF capacitor from MR to GND is recommended.