STMicroelectronics STM802SM6F

Overview

STM802SM6F from STMicroelectronics is a 3 V microprocessor supervisory IC with battery switchover, active-low RST output, manual reset (MR), watchdog timer (1.6 s typ), and power-fail comparator (PFI/PFO). It guarantees RST assertion down to VCC = 1.0 V and supports external LPSRAM non-volatilization in industrial systems requiring reliable power monitoring and backup control.

For engineers reviewing the STM802SM6F datasheet, STM802SM6F pinout, STM802SM6F application, or STM802SM6F equivalent, key selection criteria include guaranteed reset assertion at low VCC, 200 ms typical reset timeout (trec), automatic VCC-to-VBAT switchover at 2.4 V, low 40 µA supply current, and push-pull RST output compatible with standard MCU reset inputs.

Technical Context

The STM802 implements a precision voltage reference and comparator to monitor VCC against a fixed reset threshold (VRST); when VCC drops below VRST, the internal trec generator forces RST low for ≥200 ms. It integrates a 1.6 s watchdog timer cleared by WDI edge transitions - not available on STM704/795/806 variants but confirmed present in STM802 per device summary and logic diagrams.

Its dual-supply architecture enables seamless switchover from VCC to VBAT via an internal P-channel MOSFET switch (VOUT), activated when VCC falls below 2.4 V (VSW); Vccsw provides a push-pull indicator signal of switchover state, while PFI/PFO delivers early power-fail warning with 1.25 V threshold and sub-10 µs propagation delay.

Key Specifications

Pinout & Package

STM802SM6F is housed in an 8-pin SO8 (Small Outline Integrated Circuit) package, measuring 4.9 mm × 6.0 mm × 1.75 mm, with 1.27 mm lead pitch and gull-wing leads. Pin 1 is marked with a dot or notch; the package is RoHS-compliant and lead-free.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX809TRD2T and TPS3808G125DBVR, STM802SM6F uniquely integrates battery switchover, watchdog, and PFI/PFO in one SO8 package-reducing component count, PCB footprint, and qualification effort for industrial SRAM-retention systems.

Availability

STM802SM6F is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, smart energy meters, and point-of-sale terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for STM802SM6F 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 microcontrollers, power management ICs, sensors, and analog products for industrial, automotive, and consumer markets.

STM802 belongs to ST's legacy supervisor IC family targeting cost-sensitive, high-reliability embedded systems needing integrated reset, watchdog, and battery backup control without external components.

FAQ

What is the function of the Vccsw pin on STM802SM6F?

Vccsw is a push-pull output that goes high when VOUT switches from VCC to VBAT, and low when VOUT reconnects to VCC. It is designed to drive the gate of an external PMOS transistor, enabling higher current (beyond the 75 mA internal limit) to external LPSRAM during battery backup mode. Its logic state directly reflects switchover status without requiring additional sensing circuitry.

Can STM802SM6F operate without a backup battery?

Yes - STM802SM6F functions fully without VBAT. In this configuration, connect both VBAT and VOUT to VCC. The device then operates as a standard 3 V supervisor with RST, MR, WDI, and PFI/PFO functionality. Battery switchover is disabled, but all other supervision features - including reset assertion down to VCC = 1.0 V and 200 ms trec - remain active and guaranteed.

How does the watchdog timer interact with the manual reset (MR) input?

The watchdog timer is independently cleared by edges on WDI and is unaffected by MR activity. However, when MR is asserted (low), reset is immediately triggered regardless of watchdog state, and the internal timer is held inactive until MR is released. After MR returns high, the watchdog resumes counting from zero - it does not inherit elapsed time. This ensures deterministic reset behavior whether initiated by software fault or user action.

Is the PFO output compatible with 5 V logic systems?

No - PFO is a push-pull output referenced to VCC and operates within the VCC supply range (typically 2.7–5.5 V). When VCC = 3.3 V, PFO swings from 0 V to ~3.3 V; when VCC = 5 V, it swings 0–5 V. It is not 5 V-tolerant when VCC = 3.3 V, nor is it level-shifted. Direct connection to 5 V logic inputs requires an external resistor divider or buffer to avoid overvoltage damage or incorrect logic interpretation.