LTL291 Equivalent & Substitute Parts

Part Overview

The LTL291 is a red diffused through-hole LED manufactured by Lite-On Inc., designed for indication applications with a dominant wavelength of 621nm and forward voltage of 2V. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing production and maintenance applications. The LTL291 features a 3.00mm round domed lens with 8.7mcd brightness rating and 76° viewing angle, suitable for standard discrete LED indication circuits.

Substiute Parts

LTL291

Lite-On Inc.In Stock: 825LTL291 Datasheet

Current PartRFQ

LTL-4221N

Lite-On Inc.In Stock: 53128LTL-4221N Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the LTL291 is determined by the following critical parameters:

Primary Compatibility Criteria:

• Color: Red
• Lens Transparency: Diffused
• Mounting Type: Through Hole
• Forward Voltage (Vf): 2V nominal
• Lens Style: Round with Domed Top

Secondary Compatibility Criteria:

• Millicandela Rating: 8.7mcd (brightness level)
• Wavelength Range: 621-630nm dominant/peak (red spectrum)
• Viewing Angle: 76° (wide angle indication)
• Lens Size: 3.00mm diameter

The LTL-4221N qualifies as a direct substitute based on matching color, lens transparency, mounting type, forward voltage, brightness rating, and lens style. Minor variations in wavelength (625nm dominant vs. 621nm), viewing angle (60° vs. 76°), and test current (10mA vs. 20mA) remain within acceptable tolerance for red LED indication applications.

Parameter Comparison

Engineering Selection Recommendations

The LTL-4221N is the manufacturer-recommended substitute for the obsolete LTL291. Selection is based on the following engineering factors:

Product Status: The LTL291 is obsolete with limited inventory availability (732 pcs). The LTL-4221N is in active production with substantial inventory (53,100 pcs), ensuring long-term supply chain continuity.

Compliance & Certifications: The LTL-4221N meets ROHS3 and REACH compliance standards, supporting modern regulatory requirements for electronic components. These certifications are essential for applications subject to environmental and hazardous substance restrictions.

Electrical Compatibility: Both parts operate at 2V forward voltage with identical 8.7mcd brightness ratings, ensuring direct functional equivalence in indication circuits. The wavelength variation (621nm to 625nm) remains within the red spectrum and produces visually indistinguishable color output for indication applications.

Mechanical Considerations: The LTL-4221N is 0.60mm taller (5.85mm vs. 5.25mm) and features a narrower viewing angle (60° vs. 76°). These differences require verification against specific PCB layout constraints and viewing requirements in the target application.

Package Standardization: The LTL-4221N uses the standard T-1 package designation, aligning with industry-wide LED packaging conventions and improving component availability across multiple suppliers.

Frequently Asked Questions (FAQ)

Q: Can the LTL-4221N be used as a direct drop-in replacement for the LTL291?

A: The LTL-4221N is electrically and functionally equivalent for red LED indication applications. However, the 0.60mm height difference and narrower 60° viewing angle require verification against specific PCB layout and viewing geometry requirements. Physical fit and optical performance must be confirmed for the target application.

Q: What is the significance of the wavelength difference between 621nm and 625nm?

A: Both wavelengths fall within the red spectrum and produce visually identical red color output for human perception. The 4nm difference in dominant wavelength is imperceptible in indication applications and does not affect functional performance.

Q: Why is the test current different (20mA vs. 10mA)?

A: The test current specification indicates the standard operating point used for brightness measurement. The LTL-4221N achieves the same 8.7mcd brightness at 10mA, indicating improved efficiency. Both parts can operate at the same circuit current without performance degradation.

Q: Are there compliance differences between the LTL291 and LTL-4221N?

A: The LTL-4221N is certified ROHS3 compliant and REACH unaffected, meeting current environmental and hazardous substance regulations. The LTL291 compliance status is not specified. For applications requiring regulatory compliance documentation, the LTL-4221N is the appropriate choice.

Q: What viewing angle should I select for my application?

A: The LTL291 provides a 76° wide viewing angle suitable for applications requiring visibility across a broad range of angles. The LTL-4221N provides a 60° viewing angle, suitable for more focused indication. Select based on the required visibility geometry of your specific application.

Q: Is the LTL-4221N available in the same packaging as the LTL291?

A: Both parts use through-hole radial mounting. The LTL-4221N is supplied in bulk packaging, while the LTL291 packaging format is not specified. Verify packaging requirements for your procurement and assembly processes.