STMicroelectronics STM708RM6F

Overview

STM708RM6F 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 no watchdog timer. It monitors VCC for out-of-tolerance conditions down to 1.0 V and asserts RST/RST during brownout, manual reset, or power-fail detection. Used in industrial controllers and embedded systems requiring reliable power-on reset and early power-loss warning.

For engineers reviewing the STM708RM6F datasheet, STM708RM6F pinout, STM708RM6F application, or STM708RM6F equivalent, key selection criteria include its dual-reset output configuration, absence of watchdog functionality (distinguishing it from STM706 variants), PFI threshold of 1.25 V ±1%, guaranteed reset assertion at VCC ≥ 1.0 V, and TSSOP8 package compatibility with space-constrained PCB layouts.

Technical Context

The STM708RM6F implements independent voltage monitoring paths: one precision comparator for VCC supervision (VRST = 2.88–3.00 V) and a separate power-fail comparator (VPFI = 1.25 V) referenced to an internal bandgap. Its dual reset outputs (RST active-low, RST active-high) are synchronized and share identical timing behavior, enabling direct interface to microprocessors with either reset polarity requirement.

No internal watchdog timer is present - unlike STM706T/S/R/P - eliminating WDI/WDO pins and simplifying system-level watchdog management. The MR input features an internal 40 kΩ pull-up, supports TTL/CMOS logic drive, and guarantees reset assertion for trec after MR release, making external debounce unnecessary in most applications.

Key Specifications

Pinout & Package

STM708RM6F is housed in a RoHS-compliant 8-lead TSSOP package (3 mm × 3 mm body, 0.65 mm pitch), optimized for high-density PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM708RM6F, STM706SM6F adds watchdog functionality but removes PFO and dual-reset capability, while TPS3808G33DBVR reduces footprint and cost at the expense of design flexibility in reset polarity and power-fail signaling.

Availability

STM708RM6F is available at Aetrix Electronics and suitable for industrial PLCs, smart energy meters, medical handhelds, and factory automation gateways requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM708RM6F 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 automotive, industrial, and power management solutions, with over 45 years of analog and mixed-signal IC innovation.

The STM70x supervisor family targets robust power-monitoring in resource-constrained embedded systems, emphasizing precision threshold accuracy, guaranteed low-voltage reset, and minimal external component count for industrial reliability.

FAQ

What is the function of the NC pin on STM708RM6F?

Pin 8 is designated No Connect (NC) and is internally unconnected. It must remain unpopulated and unconnected on the PCB. Routing traces to or placing solder paste on this pin may cause manufacturing defects or electrical interference. The NC designation is confirmed in ST's official datasheet (DocID10518 Rev 14, Table 3) and applies exclusively to STM708 variants in TSSOP8 packaging.

Does STM708RM6F include a watchdog timer?

No. STM708RM6F explicitly omits the watchdog timer found in STM706T/S/R and STM706P variants. This is confirmed by the device summary table (Table 1), block diagram (Figure 8), and pin description table (Table 3), which show no WDI or WDO pins. The absence simplifies system watchdog architecture by delegating timing supervision to the host MCU or external circuitry.

How does the power-fail comparator interact with the reset outputs?

When PFI falls below 1.25 V, PFO goes low. If PFO is externally connected to MR, this triggers a full reset assertion on both RST and RST outputs for trec (200 ms). The PFI/PFO path operates independently of the VCC monitor - enabling early power-loss detection before VCC crosses the 2.88–3.00 V reset threshold - and is documented in Section 3.5 of the datasheet.

Can STM708RM6F operate with a 2.5 V supply?

No. STM708RM6F is specified only for 3 V operation (VCC = 3.0 V ±10%). Its reset threshold range (2.88–3.00 V) and internal reference design require nominal 3 V supply; operation at 2.5 V falls outside absolute maximum ratings and will result in undefined reset behavior, as confirmed in Section 5 (Maximum Ratings) and Section 6 (DC/AC Parameters) of DocID10518 Rev 14.