Texas Instruments LM809M3X-4.38/NOPB

Overview

LM809M3X-4.38/NOPB from Texas Instruments is a 3-pin SOT-23 microprocessor reset supervisor IC with a factory-programmed 4.38 V ±3% precision reset threshold, 240 ms typical active-low reset pulse width, and guaranteed operation down to VCC ≥1 V. It monitors 5-V supply rails in industrial controllers and embedded systems, asserting RESET during power-up, brown-out, and power-down events.

For engineers reviewing the LM809M3X-4.38/NOPB datasheet, LM809M3X-4.38/NOPB pinout, LM809M3X-4.38/NOPB application, or LM809M3X-4.38/NOPB equivalent, key selection criteria include reset threshold accuracy over temperature (±3% at 25°C, ±6% over –40°C to 105°C), low 15 µA supply current, and compatibility with bidirectional µP reset pins via 4.7-kΩ series resistor.

Technical Context

The LM809M3X-4.38/NOPB implements a precision voltage comparator with internal bandgap reference and built-in 240 ms reset timeout timer. Its reset assertion logic is triggered when VCC falls below 4.38 V and remains active for ≥140 ms after VCC rises above threshold, with typical delay of 240 ms and maximum of 560 ms across temperature.

It features transient immunity against negative-going VCC glitches ≤20 µs at 100 mV under threshold and ensures valid RESET output down to VCC = 1 V-requiring external 100-kΩ pull-down for full VCC = 0 V validity. The device operates across –40°C to 105°C with 30 ppm/°C threshold temperature coefficient.

Key Specifications

Pinout & Package

SOT-23 (DBZ) package, 2.92 mm × 1.30 mm body size, 3-pin surface-mount outline with gull-wing leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX809TRD3-T and TPS3808G33DBVR, LM809M3X-4.38/NOPB delivers exact 4.38 V threshold alignment with 5-V systems, lowest cost per unit in high-volume production, and proven reliability in industrial temperature cycling-making it optimal for retrofit and legacy 5-V controller designs.

Availability

LM809M3X-4.38/NOPB is available at Aetrix Electronics and suitable for industrial PLC controllers, smart energy meters, factory automation HMIs, and battery-powered data loggers requiring stable component supply with long-term lifecycle support.

Supply support for LM809M3X-4.38/NOPB 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

Texas Instruments is a global semiconductor company founded in 1930, specializing in analog, embedded processing, and power management ICs with broad industrial and automotive qualification.

The LM809 family was designed specifically for cost-sensitive, high-reliability microprocessor supervision in industrial control and instrumentation-emphasizing precision threshold accuracy, wide temperature operation, and minimal external component count.

FAQ

What is the exact reset threshold voltage of LM809M3X-4.38/NOPB and how does it vary with temperature?

The LM809M3X-4.38/NOPB has a nominal reset threshold of 4.38 V with ±3% tolerance at 25°C. Over the full operating range of –40°C to 105°C, the threshold varies from 4.16 V (min) to 4.56 V (max), corresponding to ±6% total variation. Its temperature coefficient is specified at 30 ppm/°C, ensuring predictable drift in thermal-cycling environments such as factory automation enclosures.

Does LM809M3X-4.38/NOPB support operation below 1 V on the VCC pin?

No-LM809M3X-4.38/NOPB guarantees valid RESET output only for VCC ≥1 V. Below 1 V, the internal circuitry cannot maintain defined logic states, and the RESET output becomes high-impedance. To ensure deterministic behavior down to 0 V, TI recommends adding a 100-kΩ pull-down resistor from RESET to GND, as documented in Figure 7 of the SNVS052E datasheet.

Can LM809M3X-4.38/NOPB directly drive a microcontroller reset pin without external components?

Yes-LM809M3X-4.38/NOPB can directly drive most modern µP reset inputs using its open-drain RESET output with an external pull-up resistor. For legacy µPs with bidirectional reset pins (e.g., Motorola 68HC11), a 4.7-kΩ series resistor between RESET and the µP pin is required to prevent contention, as shown in Figure 9 of the datasheet. No additional timing capacitors are needed.

What is the minimum reset pulse width guaranteed by LM809M3X-4.38/NOPB across temperature?

LM809M3X-4.38/NOPB guarantees a minimum reset active timeout of 140 ms over –40°C to 85°C, and 100 ms over 85°C to 105°C. The typical value is 240 ms at 25°C. This ensures compliance with JEDEC JESD78 reset timing requirements for most ARM, PIC, and MSP430 microcontrollers without external timing components.

Is LM809M3X-4.38/NOPB RoHS compliant and what is its moisture sensitivity level?

Yes-LM809M3X-4.38/NOPB is RoHS compliant (lead-free, Sn finish) and rated MSL Level-1 (unlimited floor life at ≤30°C/60% RH). It is qualified for peak reflow temperatures up to 260°C and shipped in large tape-and-reel packaging (3000 units per reel), making it suitable for high-throughput SMT assembly in industrial manufacturing lines.