STMicroelectronics STM1818TWX7F

Overview

STM1818TWX7F from STMicroelectronics is a low-power, open-drain active-low reset supervisor IC with manual reset detect functionality, designed for 3.3 V/3.0 V supply monitoring in microcontroller systems. It features a factory-trimmed 4.62 V reset threshold (±2.5% accuracy), 100 ms minimum reset pulse width, 4 µA typical supply current, and guaranteed operation down to VCC = 1.0 V over –40 °C to +105 °C. It is used in portable embedded systems requiring reliable power-on reset and user-initiated push-button recovery.

For engineers reviewing the STM1818TWX7F datasheet, STM1818TWX7F pinout, STM1818TWX7F application, or STM1818TWX7F equivalent, key selection criteria include its bidirectional RST pin with 1.5 µs manual reset detection, internal 5.5 kΩ pull-up resistor, transient-immune reset comparator, and SOT23-3 footprint compatibility with DS181x/MXD181x families.

Technical Context

The STM1818 implements a precision voltage reference and comparator to monitor VCC against a fixed 4.62 V threshold. Its reset assertion logic includes both supply-drop detection and external RST pin edge detection - a rising edge following ≥1.5 µs low pulse triggers trec = 100 ms reset hold time.

It uses an open-drain output with integrated 5.5 kΩ pull-up to VCC, enabling direct interface with bidirectional MCU reset pins without external components. The device maintains valid reset state down to VCC = 1.0 V and rejects transients ≤20 µs at 100 mV underdrive, per Figure 19 of the datasheet.

Key Specifications

Pinout & Package

STM1818TWX7F is housed in a 3-pin SOT23-3 (WX) package - compact, surface-mount, and RoHS-compliant per ECOPACK®. Pin 1 is RST (bidirectional open-drain with manual reset detect), Pin 2 is VCC (supply input and threshold reference), and Pin 3 is VSS (system ground reference).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX809SEUR+T and TPS3808G33DBVR, STM1818TWX7F uniquely combines 4.62 V threshold targeting 5 V domains, integrated manual reset detect, and bidirectional open-drain output - making it the only option among the three that eliminates external debounce and enables shared reset bus architecture.

Availability

STM1818TWX7F is available at Aetrix Electronics and suitable for industrial PLC controllers, portable medical monitors, automotive body control modules, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for STM1818TWX7F 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, specializing in microcontrollers, power management, and analog/mixed-signal ICs for industrial, automotive, and consumer markets.

STM181x is ST's low-power reset supervisor product line, engineered for high-accuracy supply monitoring and robust manual reset integration in space-constrained, battery-sensitive embedded systems.

FAQ

What is the function of the RST pin on STM1818TWX7F?

The RST pin serves a dual role: it outputs an active-low open-drain reset signal during VCC brownout, and accepts an external low pulse ≥1.5 µs to trigger manual reset. An internal 5.5 kΩ pull-up to VCC enables bidirectional use with MCUs having open-drain reset I/O, eliminating external components.

Does STM1818TWX7F require an external pull-up resistor?

No. STM1818TWX7F integrates a 5.5 kΩ pull-up resistor from RST to VCC, making external pull-up unnecessary. This allows direct connection to bidirectional MCU reset pins and simplifies board layout - confirmed in Section 1.2.4 and Figure 6 of the datasheet.

Can STM1818TWX7F operate reliably below 1.8 V supply?

Yes. STM1818TWX7F guarantees valid reset assertion down to VCC = 1.0 V across –40 °C to +105 °C (Section 2.1, p.9). Below 1.0 V, RST becomes high-impedance; for 0 V validity, a 100 kΩ pull-down is recommended per Figure 11.

How does STM1818TWX7F handle power supply transients?

It rejects negative-going VCC transients ≤20 µs duration when underdriven by 100 mV below threshold (Figure 19). This immunity is achieved via comparator hysteresis and internal filtering - verified in "Negative going VCC transients" section (p.9) and supported by 0.1 µF local bypass recommendation.