STMicroelectronics STM705DS6E

Overview

STM705DS6E from STMicroelectronics is a 5 V precision voltage supervisor IC with active-low RST and active-high RST outputs, watchdog timer (1.6 s typ), manual reset input (MR), and power-fail comparator (PFI/PFO). It guarantees RST assertion down to VCC = 1.0 V and operates from –40 °C to 85 °C in industrial applications such as microcontroller-based embedded systems requiring reliable power-on reset and brownout protection.

For engineers reviewing the STM705DS6E datasheet, STM705DS6E pinout, STM705DS6E application, or STM705DS6E equivalent, key selection criteria include its dual-reset output polarity, 4.50–4.75 V reset threshold, 200 ms typical reset timeout, push-pull WDO/RST/PFO outputs, and TSSOP8 package compatibility with space-constrained PCB layouts.

Technical Context

The STM705DS6E integrates a precision voltage reference and comparator monitoring VCC against a fixed 4.50–4.75 V reset threshold, with guaranteed RST assertion down to VCC = 1.0 V. Its internal 1.6 s watchdog timer clears on WDI edge transitions and triggers WDO low upon timeout - only effective when WDO is externally connected to MR.

It features independent power-fail detection via PFI (threshold VPFI ≈ 1.25 V) driving push-pull PFO, and supports manual reset via MR with internal 40 kΩ pull-up. All digital outputs (RST, RST, WDO, PFO) are push-pull, eliminating need for external pull-ups in most MCU interface configurations.

Key Specifications

Pinout & Package

STM705DS6E is housed in an 8-pin TSSOP package (3 mm × 3 mm body, DS suffix), optimized for high-density PCB layouts. Pin functions are validated per STMicroelectronics DocID10520 Rev 11 Figures 4 and 7.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692AESA+ and TPS3808G18DBVR, the STM705DS6E uniquely combines 5 V-specific precision reset, dual-polarity outputs, integrated watchdog, and independent power-fail detection - making it optimal for industrial 5 V MCU systems demanding comprehensive supervision in minimal area.

Availability

STM705DS6E is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, medical handheld diagnostics, and smart energy meters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for STM705DS6E 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 part of ST's dedicated power management and supervisory IC portfolio, engineered specifically for robust, low-power, multi-function reset and watchdog supervision in 5 V embedded systems.

FAQ

What is the function of the WDO pin on STM705DS6E?

The WDO (Watchdog Output) pin goes low when the WDI input remains static for ≥1.6 s, indicating a potential MCU hang. It is a push-pull output that returns high immediately upon VCC exceeding VRST - unlike RST, which stays low for trec. WDO must be externally connected to MR to trigger system reset; otherwise, it serves only as a watchdog status indicator.

Can STM705DS6E monitor a 3.3 V supply?

No - STM705DS6E is specified exclusively for 5 V operation with a reset threshold of 4.50–4.75 V. Applying 3.3 V to VCC will not assert reset and may cause undefined behavior. For 3.3 V systems, ST offers the STM708 (4.25–4.50 V threshold) or alternate supervisors like TPS3808G33.

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

PFI compares against a fixed ~1.25 V internal reference (VPFI), independent of the 4.50–4.75 V VRST threshold. This allows early detection of supply decay - e.g., configuring a resistor divider so PFI drops below VPFI milliseconds before VCC falls below VRST - enabling proactive system response rather than reactive reset.

Is the MR pin internally pulled up, and what is its impedance?

Yes - MR has an internal 40 kΩ pull-up resistor to VCC, allowing it to be left unconnected when unused. It accepts TTL/CMOS logic levels and can be driven by open-drain sources. In noisy environments, a 0.1 µF capacitor from MR to GND is recommended for immunity; no external pull-up is required.