STMicroelectronics LM317LZ

Overview

LM317LZ from STMicroelectronics is a monolithic adjustable positive voltage regulator in TO-92 package, delivering up to 100 mA output current with 1.2–37 V adjustable output range, 1.25 V internal reference voltage, and built-in thermal overload and short-circuit protection. It serves as a floating regulator in low-power industrial power supplies, battery chargers, and precision current sources.

For engineers reviewing the LM317LZ datasheet, LM317LZ pinout, LM317LZ application, or LM317LZ equivalent, key selection criteria include output voltage adjustability via resistive divider, minimum load current (3.5–5 mA), line regulation (0.01% typ), and TO-92 thermal resistance (200 °C/W).

Technical Context

The LM317LZ operates as a three-terminal floating linear regulator, using an internal 1.25 V bandgap reference between OUT and ADJ pins to set output voltage via external R1/R2 resistor divider. Its quiescent current returns entirely to the output, requiring ≥3.5 mA minimum load to maintain regulation.

It features safe-area compensation for output transistors, enabling stable operation under transient overloads. Thermal shutdown activates at junction temperatures exceeding 125 °C, and short-circuit current limiting holds output current near 100 mA regardless of output voltage.

Key Specifications

Pinout & Package

LM317LZ is supplied in JEDEC TO-92 plastic package (3-lead, through-hole), with leads formed for axial insertion. Package outline conforms to ST's mechanical data sheet DocID2168 Rev 7, Section 8.1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM317LDR2G, LM317LZ offers proven through-hole reliability and legacy compatibility; versus TLV1117-ADJ, it trades higher dropout for superior line/load regulation and simpler external component count in medium-voltage applications.

Availability

LM317LZ is available at Aetrix Electronics and suitable for industrial sensor power supplies, programmable bench power supplies, and battery charger references requiring stable component supply, long-term obsolescence support, and traceable sourcing.

Supply support for LM317LZ 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The LM317L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, low-power analog applications demanding robustness, wide voltage adjustability, and long-lifecycle availability in TO-92 and SO-8 packages.

FAQ

What is the minimum load current required for stable regulation with LM317LZ?

The LM317LZ requires a minimum load current of 3.5 mA (typical) to 5 mA (max) to maintain output 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 light-load or standby conditions-the output voltage will rise uncontrollably. A bleeder resistor from OUT to GND is commonly used to ensure compliance.

Can LM317LZ be used in high-input-voltage applications like 60 V DC input?

Yes, LM317LZ can regulate from high-input voltages provided the input-to-output differential voltage does not exceed 40 V absolute maximum. For example, with 60 V input, the output must be set ≥20 V (60 − 40 = 20). The device operates as a floating regulator, referenced only to its own OUT and ADJ pins-not system ground-making it ideal for such configurations when combined with proper input filtering and thermal management.

How does the adjustment pin current affect output voltage accuracy?

The adjustment pin draws 50–100 µA, which flows through the R2 resistor in the voltage divider, adding an error term of I_ADJ × R2 to the nominal V_OUT = 1.25 V × (1 + R2/R1). For R2 = 10 kΩ, this introduces up to 1.0 V of error. To minimize impact, R2 should be ≤2.4 kΩ (yielding ≤0.24 V error), or a buffer amplifier can be added-though most designs accept the error by selecting tighter-tolerance resistors or calibrating R1.

Is LM317LZ RoHS-compliant and halogen-free?

Yes, LM317LZ is manufactured in STMicroelectronics' ECOPACK®-compliant TO-92 package, meeting RoHS Directive 2011/65/EU and halogen-free requirements per IEC 61249-2-21. The "Z" suffix in the order code explicitly denotes the RoHS-compliant, lead-free variant. Full compliance documentation-including material declarations and test reports-is available in ST's ECOPACK® database at www.st.com.