STMicroelectronics STM690AM6F

Overview

STM690AM6F from STMicroelectronics is a 5 V microprocessor supervisory IC with battery switchover, NVRAM supervision for external LPSRAM, active-low and active-high reset outputs (RST/RST), and a 1.6 s watchdog timer. It guarantees RST assertion down to VCC = 1.0 V and features automatic VCC-to-VBAT switchover at ≤2.4 V switchover voltage. Used in industrial embedded systems requiring reliable power monitoring and SRAM backup during main supply failure.

For engineers reviewing the STM690AM6F datasheet, STM690AM6F pinout, STM690AM6F application, or STM690AM6F equivalent, key selection considerations include guaranteed reset assertion below 1.0 V VCC, 200 ms typical reset timeout (trec), low 40 µA supply current, push-pull RST/RST outputs, and integrated power-fail comparator (PFI/PFO) for early brownout warning.

Technical Context

The STM690AM6F integrates a precision voltage reference and comparator to monitor VCC against a fixed reset threshold (VRST ≈ 4.63 V), asserting RST/RST when VCC drops below VRST or after MR activation or watchdog timeout. Its internal P-channel MOSFET switch enables seamless VOUT switchover from VCC to VBAT (≤100 Ω on-resistance) when VCC falls below the lesser of VBAT or VRST.

It supports dual reset signaling (push-pull RST and RST), includes a 1.6 s typ watchdog timer cleared by WDI edge transitions, and provides a power-fail comparator with PFI input and push-pull PFO output triggered at VPFI ≈ 2.4 V or VCC < VSO. All reset outputs remain valid during battery backup mode with VBAT > 1 V.

Key Specifications

Pinout & Package

STM690AM6F is housed in an SO8 (Small Outline 8-pin) package per JEDEC MS-012, with 1.27 mm pitch, gull-wing leads, and RoHS-compliant lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM690AM6F, STM692AM6F adds watchdog capability with identical switchover and reset behavior but requires external MR biasing, while TPS3823-50DBVR omits battery management entirely - making STM690AM6F uniquely suited for NVRAM-backed industrial controllers requiring both reset integrity and power-fail foresight.

Availability

STM690AM6F is available at Aetrix Electronics and suitable for industrial PLC controllers, medical data loggers, smart energy meters, and factory automation HMIs requiring stable component supply, long-lifecycle assurance, and RoHS-compliant manufacturing.

Supply support for STM690AM6F 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, designing and manufacturing microcontrollers, power management ICs, sensors, and analog chips for industrial, automotive, and consumer markets.

The STM690A series belongs to ST's dedicated microprocessor supervisory product line, engineered specifically for robust power monitoring, non-volatile SRAM backup, and deterministic reset generation in harsh industrial environments.

FAQ

What is the guaranteed minimum VCC level at which RST remains asserted?

RST is guaranteed to be asserted (low) for any VCC between 0 V and 1.0 V when VBAT exceeds 1 V. Without battery backup, RST remains valid down to VCC = 1.0 V. This specification ensures reliable reset hold during deep brownout events common in unregulated industrial power rails.

How does the battery switchover mechanism prevent premature battery discharge during shipment?

The device inhibits VBAT-to-VOUT conduction until VCC first rises above VRST (~4.63 V), activating the "battery freshness seal" function. This prevents initial battery drain during storage or transport, enabling years of shelf life. The seal can be reinitiated per Section 2.12 of the datasheet.

Can the watchdog timer be disabled without modifying the PCB?

Yes - the watchdog timer is disabled when the WDI pin is left floating or tri-stated. With leakage current <10 µA and load capacitance <200 pF, the internal timer remains inactive. No external pull-up/down resistor is required; this allows field firmware updates to disable watchdog functionality without hardware change.

What is the maximum allowable VBAT voltage relative to VCC?

VBAT may exceed VCC without damage or functional degradation. The internal P-channel MOSFET switch isolates VBAT from VCC, allowing VBAT to be as high as 5.5 V regardless of VCC level. This supports use of higher-voltage lithium primary cells or supercapacitor banks as backup sources.