STMicroelectronics STM818MM6F

Overview

STM818MM6F from STMicroelectronics is a 5 V microprocessor supervisory IC with integrated battery switchover, chip-enable gating, and dual reset outputs (RST and RST). It provides non-volatile RAM supervision for external LPSRAM, guarantees RST assertion down to VCC = 1.0 V, features 200 ms typical reset timeout (trec), and includes a 1.6 s watchdog timer. Used in industrial embedded systems requiring reliable power monitoring and SRAM backup.

For engineers reviewing the STM818MM6F datasheet, STM818MM6F pinout, STM818MM6F application, or STM818MM6F equivalent, key selection criteria include chip-enable gating propagation delay (7 ns max), battery switchover threshold behavior, push-pull reset output drive strength, and compatibility with LPSRAM write-protection timing requirements.

Technical Context

The STM818MM6F implements a precision voltage comparator monitoring VCC against a 4.65 V reset threshold (VRST) with hysteresis, and uses a P-channel MOSFET switch (100 Ω typical on-resistance) for automatic VCC-to-VBAT switchover at the lesser of VRST or VBAT. Its watchdog timer triggers reset if WDI remains static for ≥1.6 s (typ), and is cleared by edge transitions.

Unlike other members of the family (e.g., STM817/819), STM818 includes dedicated E (chip-enable input) and ECON (conditioned chip-enable output) pins enabling gated access to external LPSRAM during reset assertion - ECON goes low only when E is low *and* reset is de-asserted, with 15 µs minimum pulse width guarantee.

Key Specifications

Pinout & Package

STM818MM6F is housed in an SO8 (Small Outline, 8-pin) package per JEDEC MS-012, with 1.27 mm pitch and gull-wing leads. Pin assignments are validated per ST's DocID10522 Rev 11 (Table 3, Figure 6).

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM817MM6F and STM819MM6F, STM818MM6F uniquely combines watchdog supervision, dual reset outputs, and sub-7 ns chip-enable gating - making it the only option in the family for time-critical LPSRAM write-protection during reset events.

Availability

STM818MM6F is available at Aetrix Electronics and suitable for industrial PLC memory backup, medical device data retention, smart meter firmware recovery, and automated test equipment calibration storage requiring stable component supply and long-term lifecycle support.

Supply support for STM818MM6F 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.

STM818MM6F belongs to ST's supervisor IC product line, engineered specifically for robust non-volatile memory supervision in industrial and medical systems requiring guaranteed reset behavior, battery-backed SRAM integrity, and precise timing control.

FAQ

What is the function of the E and ECON pins on STM818MM6F?

E is the chip-enable input that controls gating logic; ECON is the conditioned output that goes low only when E is low *and* reset is de-asserted. This ensures LPSRAM access is blocked during reset assertion, preventing data corruption. ECON remains low for 15 µs or until E rises, whichever occurs first - a timing guarantee critical for synchronous SRAM interfaces.

Does STM818MM6F support power-fail detection like STM817?

No. STM818MM6F does not include PFI (power-fail input) or PFO (power-fail output) functionality - those pins are omitted per device summary Table 1 and confirmed in Figure 3 and Section 2.8. Power-fail comparator capability is present in STM817/819 but explicitly excluded from STM818 to prioritize chip-enable gating and watchdog features.

Can STM818MM6F operate without a backup battery?

Yes. When no battery is used, connect both VBAT and VOUT to VCC. The device operates normally as a 5 V supervisor with RST/RST outputs, watchdog, and chip-enable gating. Battery switchover is disabled, but all other functions - including reset assertion down to VCC = 1.0 V - remain fully operational per datasheet Section 2.1.

How is the reset timeout (trec) triggered and what determines its duration?

trec is generated by an internal timer that starts when VCC rises above the 4.65 V reset threshold (VRST) and holds RST/RST asserted for 200 ms (typ). It also triggers on MR low-to-high transition or watchdog timeout. Duration is fixed and factory-trimmed - not adjustable externally - ensuring consistent reset hold time across temperature (–40 °C to +85 °C) and supply voltage variations.