STMicroelectronics LM217LZ-TR

Overview

LM217LZ-TR from STMicroelectronics is a monolithic adjustable positive voltage regulator in TO-92 package, delivering up to 100 mA output current with 1.2 V to 37 V adjustable output range, ±0.7% output voltage temperature stability, and built-in thermal overload and short-circuit protection. It operates in floating configuration for high-voltage applications such as industrial power supplies and programmable lab bench supplies.

For engineers reviewing the LM217LZ-TR datasheet, LM217LZ-TR pinout, LM217LZ-TR application, or LM217LZ-TR equivalent, key selection criteria include minimum load current (3.5–5 mA), reference voltage accuracy (1.2–1.3 V), line regulation (0.01–0.02 %/V typ.), and thermal resistance (200 °C/W junction-to-ambient in TO-92).

Technical Context

The LM217LZ-TR implements a bandgap-referenced feedback control loop with internal current limiting and thermal shutdown. Its 1.25 V nominal reference voltage (VREF) is used with an external resistive divider to set output voltage per VO = VREF × (1 + R2/R1) + IADJ × R2, where IADJ ≤ 100 µA ensures minimal error contribution.

It features floating operation-only sensing input-to-output differential voltage (max 40 V)-enabling high-side regulation without ground-referenced constraints. Protection circuitry includes safe-area compensation for output transistors and foldback current limiting during overload or short-circuit conditions.

Key Specifications

Pinout & Package

LM217LZ-TR is supplied in TO-92 plastic package (3-lead, through-hole), with leads arranged in standard linear regulator orientation: Pin 1 = Adjust, Pin 2 = Input, Pin 3 = Output. The package provides 200 °C/W junction-to-ambient thermal resistance when mounted on standard PCB without heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM317LZ-TR and TLV1117-33CKC, LM217LZ-TR uniquely supports industrial temperature range, full 1.2–37 V adjustability, and floating high-voltage operation-making it irreplaceable for programmable supplies and sensor biasing in harsh environments.

Availability

LM217LZ-TR is available at Aetrix Electronics and suitable for industrial sensor power supplies, programmable lab bench supplies, low-power microcontroller peripherals, and LED biasing circuits requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM217LZ-TR 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, microcontroller, and sensor solutions for automotive, industrial, and consumer markets.

The LM217L/LM317L series belongs to ST's legacy linear regulator product line, engineered specifically for simplicity, reliability, and wide-input-range adaptability in cost-sensitive industrial and instrumentation applications.

FAQ

What is the minimum load current required for stable regulation with LM217LZ-TR?

The LM217LZ-TR requires a minimum load current of 3.5 mA (typ.) to 5 mA (max.) to maintain regulation. This is due to its internal quiescent current being returned to the output terminal. If load current falls below this threshold-such as when driving high-impedance inputs-the output voltage will rise uncontrollably. A bleeder resistor is commonly added to ensure compliance.

Can LM217LZ-TR be used in floating (high-side) configurations?

Yes. The LM217LZ-TR regulates based solely on the voltage difference between its input and output pins (VI–VO), not ground-referenced potentials. As long as VI–VO remains within 3–40 V and thermal limits are observed, it can regulate outputs hundreds of volts above ground-ideal for battery chargers, photomultiplier supplies, and isolated auxiliary rails.

How does the adjustment pin current affect output voltage accuracy?

The adjustment pin draws 50–100 µA (IADJ), which flows through the R2 resistor in the feedback divider, adding an error term IADJ × R2 to the ideal VO = VREF × (1 + R2/R1). For example, with R2 = 10 kΩ and IADJ = 100 µA, this introduces a 1 V offset. Selecting lower R2 values or compensating in design mitigates this effect while balancing power loss and noise sensitivity.

What thermal considerations apply when using LM217LZ-TR in TO-92 package?

In TO-92, the LM217LZ-TR has a junction-to-ambient thermal resistance of 200 °C/W. At 100 mA output and 10 V drop (1 W dissipation), junction temperature rises ~200 °C above ambient-exceeding the 125 °C limit. Derating is essential: maximum continuous power is ~375 mW (e.g., 75 mA @ 5 V drop) without PCB copper heatsinking. Adding ≥1 cm² of 2-oz copper significantly improves thermal performance.