STMicroelectronics LM217T

Overview

LM217T from STMicroelectronics is a monolithic adjustable positive voltage regulator in TO-220 single-gauge package, delivering >1.5 A output current with 1.2–37 V adjustable output range, 0.1% line/load regulation, and integrated thermal shutdown, current limiting, and safe operating area (SOA) control-used in industrial power supplies, lab bench adapters, and programmable DC sources.

For engineers reviewing the LM217T datasheet, LM217T pinout, LM217T application, or LM217T equivalent, this page provides verified pin functions, thermal resistance values (R_thJC = 5 °C/W), reference voltage (1.25 V), minimum load current (3.5 mA), and SOA-protected operation for high-voltage floating configurations.

Technical Context

The LM217T implements a bandgap-referenced error amplifier driving a series pass transistor, with all quiescent current returned to the output to maintain regulation under light loads. Its internal 1.25 V reference is measured between OUTPUT and ADJUST pins, enabling precise resistive divider-based voltage setting.

It operates as a floating regulator: only the input-to-output differential voltage (up to 40 V) matters-not absolute input voltage-allowing high-side regulation in systems with elevated ground potentials. Protection circuitry actively limits current, disables conduction above 150 °C junction temperature, and enforces SOA compliance during transient overload.

Key Specifications

Pinout & Package

LM217T uses TO-220 single-gauge package (ECOPACK® compliant), with metal tab electrically connected to OUTPUT pin and optimized for vertical mounting on heatsinks. Thermal resistance is R_thJC = 5 °C/W and R_thJA = 50 °C/W (with 1 in² copper pad).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable linear regulator applications.

Compared with LM317T, LM217T trades −40 °C capability for +150 °C robustness-making it optimal for enclosed, high-power industrial enclosures. Compared with LM317B, it offers superior thermal resilience at elevated temperatures but lacks sub-zero startup assurance.

Availability

LM217T is available at Aetrix Electronics and suitable for industrial power supplies, programmable DC chargers, high-voltage floating regulators, and precision current sources requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM217T 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, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The LM217T belongs to ST's legacy linear regulator product line, engineered specifically for ruggedized industrial power conversion where thermal resilience, SOA integrity, and floating topology support are prioritized over ultra-low quiescent current or digital interface features.

FAQ

What is the minimum load current required for stable regulation?

The LM217T requires a minimum load current of 3.5 mA at VI–VO = 40 V to maintain regulation. This is due to its architecture routing all quiescent current to the OUTPUT pin. If load current falls below this threshold-such as in standby mode-the output voltage will rise uncontrollably. A bleeder resistor (e.g., 360 Ω/1 W from OUTPUT to GND) is mandatory in low-load applications.

Can LM217T be used in parallel for higher current output?

No-LM217T is not designed for direct paralleling. Its output voltage tolerance (±1%) and load regulation (5–15 mV) cause current imbalance, risking thermal runaway in one device. For >1.5 A, use a single LM217T with an external pass transistor (as shown in ST's AN282 application note) or select a higher-current regulator like ST's L200.

What thermal derating applies above 25°C ambient?

With the standard TO-220 footprint (1 in² copper), R_thJA = 50 °C/W. At 75 °C ambient, maximum allowable power dissipation drops to (150 °C – 75 °C) / 50 °C/W = 1.5 W. For 1.5 A output at 5 V dropout, that limits usable current to ~300 mA unless a heatsink reduces R_thJA. Derating curves are provided in Figure 4 of DS0433.

Is an input bypass capacitor mandatory?

Yes-a minimum 0.1 µF ceramic capacitor placed within 1 cm of the INPUT pin is mandatory to prevent oscillation and ensure stability, especially with long input traces or high-impedance sources. Larger electrolytic capacitors (e.g., 10–100 µF) may be added for bulk filtering but do not replace the high-frequency ceramic requirement.