STMicroelectronics STM817LM6F

Overview

STM817LM6F from STMicroelectronics is a 5 V microprocessor supervisory IC with integrated battery switchover, power-fail comparator (PFI/PFO), and watchdog timer (1.6 s typ). It provides active-low and active-high reset outputs (RST/RST), guarantees RST assertion down to VCC = 1.0 V, and supports external LPSRAM non-volatilization via VOUT switching. Used in industrial embedded systems requiring reliable power monitoring and SRAM backup during main supply failure.

For engineers reviewing the STM817LM6F datasheet, STM817LM6F pinout, STM817LM6F application, or STM817LM6F equivalent, this page delivers verified technical context, SO8 package mapping, reset timing behavior, battery switchover logic, and functional alternatives for NVRAM supervisor selection in 5 V systems.

Technical Context

The STM817LM6F implements dual-reset supervision with push-pull RST and RST outputs, a precision voltage comparator monitoring VCC against VRST (typically 4.63 V), and automatic switchover from VCC to VBAT on VOUT when VCC drops below the lesser of VRST or VBAT (VSO). Its internal watchdog timer triggers reset if WDI remains static for ≥1.6 s (typ), and it asserts PFO low when PFI < VPFI (typically 2.4 V) or VCC falls below VSO.

It features battery freshness seal functionality, low quiescent current (40 µA typ at VCC = 5 V, 0.4 µA typ in battery backup), and guaranteed reset assertion during power-up, brownout, and manual reset via MR. All I/Os are TTL/CMOS-compatible with internal pull-ups on MR and E pins.

Key Specifications

Pinout & Package

STM817LM6F is housed in an industry-standard SO8 (Small Outline 8-pin) package, 3.9 mm × 4.9 mm body, 1.27 mm pitch, RoHS-compliant and lead-free.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 5 V NVRAM supervisor applications.

Compared with MAX692A and TPS3808G18, STM817LM6F uniquely integrates VOUT-based battery switchover, PFI/PFO dual-rail monitoring, and battery freshness seal-making it the only option among the three that fully supports autonomous, long-life NVRAM backup in industrial 5 V systems.

Availability

STM817LM6F is available at Aetrix Electronics and suitable for industrial PLCs, smart meters, medical diagnostics, and point-of-sale terminals requiring stable component supply, long-lifecycle assurance, and RoHS-compliant manufacturing.

Supply support for STM817LM6F 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 devices for industrial, automotive, and consumer markets.

The STM690/703/802/817 family was engineered specifically for robust 5 V microprocessor supervision with integrated SRAM backup-targeting applications where data integrity during power disruption is mission-critical.

FAQ

What is the function of the E and ECON pins on STM817LM6F?

The STM817LM6F does not include E or ECON pins. Those signals are exclusive to the STM818 variant, which adds chip-enable gating for external LPSRAM. STM817LM6F omits this feature and instead focuses on core supervision: reset generation, battery switchover, watchdog, and power-fail detection. Pin count and functionality align strictly with the 8-pin SO8 configuration shown in Table 3 of DocID10522 Rev 11.

Can STM817LM6F supervise a 3.3 V microcontroller supply?

No-STM817LM6F is specified only for 5 V operation (VCC = 4.5–5.5 V) and has a fixed 4.63 V reset threshold. It cannot reliably monitor 3.3 V rails. For 3.3 V systems, ST offers the STM809 (3.08 V threshold) or STM810 (2.93 V), but those lack battery switchover and PFI/PFO. Supervising mixed-voltage systems requires separate supervisors per rail or a multi-threshold device like the STM805 (dual 5 V/3.3 V variants).

How does the battery freshness seal work, and how is it activated?

The battery freshness seal prevents VBAT discharge during storage by disabling the internal switchover FET until first power-up. It activates automatically when VCC rises above VRST (4.63 V) for the first time-connecting VBAT to the internal circuitry. Once sealed, the device draws only 0.4 µA from the battery. This ensures full shelf life (≥10 years) and eliminates need for battery removal prior to shipment.

Is the watchdog timer disabled by default, and how is it enabled?

The watchdog timer is enabled by default and requires periodic WDI toggling (high-to-low or low-to-high) every ≤1.6 s to prevent reset assertion. To disable it, float the WDI pin-its high-impedance state stops timer counting. No configuration register or external component is needed. Disabling is confirmed by absence of reset pulses when WDI is left unconnected and VCC is stable.