STMicroelectronics STM706RDS6F

Overview

STM706RDS6F from STMicroelectronics is a precision 3 V supply voltage supervisor IC with active-low reset output, watchdog timer, manual reset input, and power-fail comparator. It asserts RST low for ≥200 ms when VCC drops below 2.59–2.70 V, supports watchdog timeout at 1.6 s (typ.), draws only 40 µA (typ.) supply current, and operates from –40 °C to +85 °C. It is used in industrial controllers to ensure reliable microprocessor reset during brownout or software lockup.

For engineers reviewing the STM706RDS6F datasheet, STM706RDS6F pinout, STM706RDS6F application, or STM706RDS6F equivalent, key selection criteria include reset threshold accuracy, guaranteed RST assertion down to VCC = 1.0 V, push-pull RST/RST/WDO/PFO outputs, trec timing stability over temperature, and compatibility with bi-directional MCU reset pins via series resistor interface.

Technical Context

The STM706RDS6F integrates a precision bandgap-based voltage reference and comparator to monitor VCC against a fixed 2.59–2.70 V reset threshold. Its internal reset timeout generator ensures ≥200 ms RST pulse width after power-up or MR release, independent of VCC slew rate.

It implements a 1.6 s (typ.) watchdog timer cleared by WDI edge transitions; WDO is a push-pull output that can be looped to MR for autonomous system recovery. The PFI/PFO pair provides independent undervoltage detection using a 1.25 V (typ.) reference, decoupled from the main reset comparator.

Key Specifications

Pinout & Package

STM706RDS6F is housed in an 8-pin TSSOP package (3 × 3 mm body, DS suffix), optimized for space-constrained PCB layouts while maintaining thermal and electrical performance comparable to SO8.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM706TDS6F, the STM706RDS6F offers lower reset threshold for earlier intervention in 3 V systems, while the TPS3808G12DBVR trades integrated watchdog capability for threshold flexibility and slightly lower I_CC, making it suitable for simpler monitoring tasks where software-level watchdogs already exist.

Availability

STM706RDS6F is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, smart energy meters, and automated test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM706RDS6F 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 designing and manufacturing microcontrollers, analog ICs, power management devices, and sensors for industrial, automotive, and consumer applications.

The STM70x series is a dedicated family of voltage supervisors engineered for robust, single-chip power monitoring in resource-constrained embedded systems - emphasizing precision thresholding, guaranteed low-VCC operation, and integrated fault-detection features like watchdog and power-fail comparison.

FAQ

What is the function of the WDO pin on STM706RDS6F?

The WDO (Watchdog Output) pin is a push-pull active-low output that asserts when the WDI pin remains static for ≥1.6 s (typ.), indicating a potential MCU firmware hang. It de-asserts immediately upon detecting an edge on WDI or when VCC rises above the reset threshold. WDO can be connected to MR to generate an autonomous hardware reset without processor intervention.

Can STM706RDS6F be used with a microcontroller that has a bidirectional reset pin?

Yes - connect a 4.7 kΩ series resistor between STM706RDS6F's RST pin and the MCU's bidirectional reset I/O. This prevents signal contention when both devices attempt to drive the line simultaneously. The resistor value ensures adequate noise immunity while allowing the MCU to override reset during debug or recovery sequences without loading the supervisor output.

How does the PFI/PFO function differ from the main VCC reset monitoring?

PFI/PFO uses a separate 1.25 V internal reference and comparator, independent of the 2.59–2.70 V VCC reset threshold. This allows PFI to monitor a different rail (e.g., unregulated input or battery voltage) and assert PFO before VCC drops to the reset level - enabling early-warning shutdown or data save operations. PFO is push-pull and can directly drive MR for cascaded reset initiation.

Is the MR pin internally pulled up, and what happens if left unconnected?

Yes, MR has a 40 kΩ internal pull-up resistor to VCC. If left unconnected (floating), MR remains logic high and does not trigger reset. This eliminates the need for an external pull-up in most designs. For noisy environments or long PCB traces, a 0.1 µF capacitor from MR to GND is recommended to suppress EMI-induced glitches.