Texas Instruments LM309H/NOPB

Overview

LM309H/NOPB from Texas Instruments (formerly National Semiconductor) is a fixed +5 V monolithic linear voltage regulator in a TO-39 metal can package, delivering up to 200 mA output current with internal thermal shutdown and foldback current limiting. It operates from 7.4 V to 25 V input, maintains ±3% output voltage accuracy over temperature and load, and is designed for local regulation on TTL/DTL logic cards.

For engineers reviewing the LM309H/NOPB datasheet, LM309H/NOPB pinout, LM309H/NOPB application, or LM309H/NOPB equivalent, key selection considerations include its 0°C to +125°C operating junction temperature range, 15 °C/W junction-to-case thermal resistance, no-external-components operation, and compatibility with legacy 5 V digital systems requiring robust overcurrent and thermal protection.

Technical Context

The LM309H/NOPB implements a single-chip series pass regulator with built-in current-limiting circuitry that folds back output current under overload to limit power dissipation, and a thermal shutdown mechanism that disables the pass transistor when junction temperature exceeds ~175°C. Its reference and error amplifier are integrated on the same die as the power transistor.

Stability is achieved without external compensation: the device exhibits inherent phase margin across its rated load (5 mA–200 mA) and input voltage (7.4 V–25 V) ranges, and provides ≥50 dB ripple rejection at 120 Hz. Output noise is specified at 40 µV RMS (10 Hz–100 kHz), supporting low-noise digital supply applications.

Key Specifications

Pinout & Package

LM309H/NOPB uses a hermetically sealed TO-39 metal can package (NS package code H03A) with three leads. Pin 3 is electrically connected to the case and must be grounded for proper thermal and electrical operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed +5 V linear regulator applications.

Compared with LM7805K and MC7805CD2TR4, the LM309H/NOPB offers superior reliability in harsh environments via its hermetic TO-39 metal can, guaranteed 0°C to +125°C operation, and proven field history in legacy military and industrial systems-making it the preferred choice when long-term availability and ruggedness outweigh raw current capability or SMT compatibility.

Availability

LM309H/NOPB is available at Aetrix Electronics and suitable for industrial control logic power, military data acquisition systems, legacy computer backplane regulation, and test equipment digital subsystems requiring stable component supply and long-lifecycle support.

Supply support for LM309H/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 (TI) acquired National Semiconductor in 2011 and maintains its legacy analog product lines, including precision regulators and power management ICs, with full datasheet, packaging, and reliability documentation.

The LM309H/NOPB belongs to TI's legacy linear regulator portfolio, originally developed for high-reliability local regulation in TTL/DTL logic systems where thermal robustness, hermetic packaging, and minimal external components were critical design requirements.

FAQ

What is the maximum input voltage for LM309H/NOPB?

The absolute maximum input voltage for LM309H/NOPB is 35 V, but the recommended operating range is 7.4 V to 25 V per the Electrical Characteristics table. Operation above 25 V increases thermal stress and reduces safe output current capability. The device's internal protection prevents catastrophic failure, but sustained operation near 35 V may trigger thermal shutdown under load. Always refer to the derating curves in the SNVS752A datasheet for continuous operation limits.

Does LM309H/NOPB require an output capacitor for stability?

No, LM309H/NOPB does not require an output capacitor for stability-the device is internally compensated and remains stable from no load to full 200 mA load without external capacitance. However, adding a 1–10 µF solid tantalum or ceramic capacitor at the output improves transient response during fast load steps, especially in systems with long PCB traces between regulator and load. This is explicitly noted in the Typical Applications section of the SNVS752A datasheet.

What is the operating temperature range of LM309H/NOPB?

The LM309H/NOPB has an operating junction temperature range of 0°C to +125°C, as confirmed in the Absolute Maximum Ratings table of SNVS752A. This distinguishes it from the LM109H (−55°C to +150°C) and defines its suitability for commercial and industrial-but not military-environments. Ambient temperature limits depend on power dissipation and heatsinking; the TO-39 package's 15 °C/W θ_JC must be combined with system-level thermal resistance to calculate actual usable ambient range.

Is LM309H/NOPB pin-compatible with LM7805?

No, LM309H/NOPB is not pin-compatible with LM7805. LM309H/NOPB uses a TO-39 metal can package with Input–Output–Ground pinout (viewed from bottom: Pin 1 = Input, Pin 2 = Output, Pin 3 = Ground/case), while LM7805 in TO-220 uses Input–Ground–Output and in TO-3 uses Input–Output–Ground but with larger spacing and different mechanical footprint. Substitution requires PCB layout changes and thermal redesign due to differing θ_JC (15 °C/W vs. 5 °C/W for TO-220) and current capability.

What protection features does LM309H/NOPB include?

LM309H/NOPB integrates two key protection features: foldback current limiting and thermal shutdown. Foldback limiting reduces short-circuit current as input-output differential rises, minimizing power dissipation during faults. Thermal shutdown disables the output when junction temperature exceeds ~175°C, allowing cooldown before automatic recovery. Both functions are fully internal-no external components needed. These protections are documented in the General Description and Absolute Maximum Ratings sections of SNVS752A and validated across the full 0°C to +125°C operating range.