STMicroelectronics M40Z300WMH6F

Overview

M40Z300WMH6F from STMicroelectronics is a 3.0 V to 3.6 V non-volatile RAM (NVRAM) supervisor IC that converts low-power SRAMs into battery-backed memory by managing power-fail detection, automatic write-protection, and seamless VCC-to-battery switchover. It supports up to eight SRAMs via dual-device parallel decoding, features open-drain RST and BL outputs, and delivers ≤12 ns chip enable propagation delay. Used in industrial data loggers requiring persistent memory during brownouts.

For engineers reviewing the M40Z300WMH6F datasheet, M40Z300WMH6F pinout, M40Z300WMH6F application, or M40Z300WMH6F equivalent, key selection criteria include VPFD threshold select (THS), VSO switchover voltage, tWPT write-protect timing, battery low monitoring interval, and SOIC-16 package compatibility with external lithium cell connections.

Technical Context

The M40Z300WMH6F implements precision voltage monitoring using an internal reference and comparator to detect VCC out-of-tolerance conditions below VPFD (2.5 V–2.7 V when THS = VOUT). Upon detection, it forces E1CON–E4CON inactive within tWPT (≤10 µs) to unconditionally write-protect attached SRAMs.

It integrates a bidirectional power switch that disconnects VCC and connects the external battery to VOUT at VSO (≈2.3 V), sustaining SRAM data retention at VOHB ≥ 2.0 V. The 2-input A/B decoder enables independent control of four SRAMs per device, scalable to eight with parallel placement.

Key Specifications

Pinout & Package

Package: 16-lead SOIC (SO16/MQ), body width 150 mils, RoHS-compliant lead-free finish. Designed for direct connection to external lithium battery via dedicated B+ and B– pins (pins 9 and 8 respectively); B– must not be tied to VSS.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6900 and DS1230Y, the M40Z300WMH6F uniquely combines 3.0 V operation, field-replaceable battery interface, programmable VPFD, and 4-SRAM decode in a compact SO16 package-making it optimal for space-constrained, multi-SRAM embedded systems requiring long-term data retention and serviceability.

Availability

M40Z300WMH6F is available at Aetrix Electronics and suitable for industrial data loggers, medical device memory backup, avionics black box recorders, and smart meter firmware retention requiring stable component supply and long-lifecycle support.

Supply support for M40Z300WMH6F 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 memory solutions for industrial, automotive, and consumer markets.

The M40Z300WMH6F belongs to ST's NVRAM supervisor product line, engineered specifically to convert standard low-power SRAMs into robust, battery-backed non-volatile memory subsystems for mission-critical data retention in harsh or unreliable power environments.

FAQ

What is the function of the THS pin on the M40Z300WMH6F?

The THS (Threshold Select) pin configures the power-fail detection voltage (VPFD) range: when tied to VSS, VPFD is 2.8 V–3.0 V; when tied to VOUT, VPFD is 2.5 V–2.7 V. This allows precise alignment with system brownout thresholds and ensures write-protection triggers before SRAM data retention fails. THS must be hard-wired to either VSS or VOUT-floating is not permitted.

Can the M40Z300WMH6F support more than four SRAMs?

Yes-two M40Z300WMH6F devices can be placed in parallel using shared A/B decoder inputs and separate E1CON–E4CON outputs to control up to eight SRAMs. Each device drives four unique CE lines, and the dual-device configuration maintains independent power-fail response and battery switchover per SRAM group.

Why must B– be isolated from VSS on the M40Z300WMH6F?

B– is the dedicated cathode connection for the external lithium battery and must not be tied to VSS to prevent parasitic discharge paths through internal protection circuitry. Connecting B– to VSS violates the absolute maximum rating for pin voltage and risks premature battery depletion, especially during backup mode when VCC is absent and internal leakage paths dominate.

How does the BL (Battery Low) pin behave during power-up versus periodic monitoring?

During power-up, BL asserts immediately if battery voltage is <2.5 V-indicating potential data integrity risk. During periodic 24-hour checks, BL assertion signals end-of-life but does not compromise data since VCC remains active. In both cases, BL is open-drain and requires a pull-up resistor to VCC; replacement must occur with VCC applied to reinitialize monitoring.