Texas Instruments LM317LILPE3

Overview

LM317LILPE3 from Texas Instruments is a 3-terminal, adjustable positive-voltage linear regulator delivering up to 100mA output current with 1.25V to 37V programmable output voltage range. It uses floating topology, sees only input-to-output differential voltage (max 45V), and requires no output capacitor for stability. It serves as a precision voltage or current regulator in low-power industrial power supplies and analog sensor conditioning circuits.

For engineers reviewing the LM317LILPE3 datasheet, LM317LILPE3 pinout, LM317LILPE3 application, or LM317LILPE3 equivalent, key selection considerations include its TO-92 package thermal performance (R_θJA = 139.5°C/W), 1.25V reference voltage tolerance (±0.006V), adjustment pin current (44–57µA), and dropout headroom requirement (2.5V min).

Technical Context

The LM317LILPE3 implements an NPN Darlington pass element with internal 1.25V bandgap reference and feedback amplifier. Its floating architecture enables high-voltage operation (e.g., regulating 300V input with 37V output) as long as VI–VO ≤ 45V. Regulation is achieved by sourcing output current to maintain 1.25V between OUTPUT and ADJUST pins.

It integrates overcurrent and thermal-overload protection that remains active even if ADJUST is disconnected. The device operates without mandatory output capacitance but supports optional C_ADJ (10µF) to boost ripple rejection to 71.5dB at 120Hz - a feature enabled by direct adjustment-pin bypassing not available in fixed-output regulators.

Key Specifications

Pinout & Package

LM317LILPE3 is packaged in TO-92 (LP) - a 3-pin through-hole plastic package measuring 4.8mm × 3.68mm, optimized for manual assembly and low-cost PCBs. Thermal resistance is R_θJA = 139.5°C/W (legacy chip, CSO:SHE), suitable for natural-convection cooling at ≤60mW dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM317LILPE3, LM317LDR2G offers superior thermal dissipation in compact SMT form, while TLV1117LV33DCYR trades adjustability and floating capability for higher current and lower dropout - making them complementary rather than drop-in replacements.

Availability

LM317LILPE3 is available at Aetrix Electronics and suitable for solar energy charge control, HVAC sensor power supplies, optical network terminal units (ONT), and analog input modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM317LILPE3 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 leader designing analog ICs, embedded processors, and system-on-chip solutions for industrial, automotive, and communications markets.

The LM317L series was developed as a robust, low-cost, adjustable linear regulator family targeting industrial power management where reliability, wide input range, and floating operation are essential - especially in legacy and cost-sensitive designs.

FAQ

What is the maximum input-to-output differential voltage for LM317LILPE3?

The LM317LILPE3 supports a maximum input-to-output differential voltage of 45V (CSO:RFB fabrication). This rating enables use in high-side floating configurations - for example, regulating a 300V input down to 255V output - provided the absolute maximum junction temperature (150°C) is not exceeded and thermal design accounts for PD = (VI–VO) × IO.

Does LM317LILPE3 require an output capacitor to maintain stability?

No, LM317LILPE3 does not require an output capacitor for stability - a key differentiator from most LDOs. Its internal compensation ensures unconditional stability with or without C_OUT. However, adding a 1µF output capacitor improves transient response during load steps, and a 10µF capacitor on the ADJUST pin significantly enhances ripple rejection (up to 71.5dB at 120Hz).

How do I configure LM317LILPE3 as a constant-current source?

To configure LM317LILPE3 as a constant-current source, connect a single resistor R between the ADJUST and OUTPUT pins. Set R = 1.25V / I_OUT (e.g., 25Ω for 50mA). The device regulates so that 1.25V appears across R, delivering precise I_OUT independent of load voltage - ideal for LED biasing or battery trickle charging. Ensure R's power rating exceeds (1.25V)²/R.

What is the typical adjustment pin current for LM317LILPE3, and why does it matter?

The LM317LILPE3 has a typical adjustment pin current of 44µA (range 44–57µA). This current flows out of the ADJUST pin and into the feedback resistor network. It introduces a small error in output voltage calculation (V_OUT = 1.25V × (1 + R2/R1) + I_ADJ × R2), which becomes significant only when R2 exceeds ~10kΩ. For best accuracy, keep R2 ≤ 2.4kΩ or compensate mathematically.

Can LM317LILPE3 be used in high-temperature industrial environments?

Yes, LM317LILPE3 is specified for operation from –40°C to +125°C junction temperature. In TO-92 package (LP), its R_θJA = 139.5°C/W means it can deliver full 100mA at ambient up to +60°C with no heatsink, or up to +85°C with modest PCB copper area. Derating curves in the datasheet confirm reliable operation across industrial temperature grades when power dissipation is managed per PD = (VI–VO) × IO.