SIR-341ST3FF Equivalent & Substitute Parts

Part Overview

The SIR-341ST3FF is an infrared (IR) emitter manufactured by Rohm Semiconductor, designed for 940nm wavelength applications requiring 75mA maximum forward current. This component operates at a typical forward voltage of 1.3V with a radiant intensity of 5.6mW/sr at 50mA and a 32° viewing angle in T-1 through-hole packaging.

The SIR-341ST3FF is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain reliability, and support ongoing production or maintenance requirements for systems utilizing this component.

Substiute Parts

SIR-341ST3FF

Rohm SemiconductorIn Stock: 656SIR-341ST3FF Datasheet

Current PartRFQ

LTE-3271B

Lite-On Inc.In Stock: 1171LTE-3271B Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SIR-341ST3FF is determined by the following critical parameters:

• Wavelength: Must be 940nm to maintain spectral compatibility with receiver circuits and optical filters
• Current Rating: Forward current capacity must meet or exceed the design requirement of 75mA
• Forward Voltage: Operating voltage must be compatible with the circuit's power supply and current-limiting resistor design
• Radiant Intensity: Output power must satisfy the application's signal detection requirements
• Viewing Angle: Beam divergence affects optical coupling efficiency and must be compatible with the optical path design
• Mounting Type & Package: Through-hole mounting is required for mechanical and electrical compatibility

The LTE-3271B from Lite-On Inc. is identified as a substitute based on matching wavelength (940nm), through-hole mounting, and compatible operating temperature range. Differences in current rating, forward voltage, radiant intensity measurement conditions, viewing angle, and package form factor (Radial vs. T-1) must be evaluated against specific circuit requirements.

Parameter Comparison

Engineering Selection Recommendations

Both the SIR-341ST3FF and LTE-3271B are ROHS3 compliant and operate within compatible temperature ranges. The LTE-3271B offers an extended lower operating temperature limit (-40°C vs. -25°C), providing broader environmental coverage.

The LTE-3271B is classified as active product status, ensuring ongoing availability and supply chain support compared to the obsolete SIR-341ST3FF. Selection between these parts must account for mechanical fit (T-1 vs. Radial package), optical beam characteristics (32° vs. 50° viewing angle), and circuit-level current and voltage compatibility.

Frequently Asked Questions (FAQ)

Q: Can the LTE-3271B directly replace the SIR-341ST3FF in existing PCB designs?

A: Direct replacement requires verification of mechanical fit. The LTE-3271B uses Radial through-hole mounting, while the SIR-341ST3FF uses T-1 through-hole packaging. PCB footprints and lead spacing must be confirmed compatible. Additionally, the wider 50° viewing angle of the LTE-3271B may affect optical coupling efficiency compared to the 32° angle of the original part.

Q: What are the implications of the different forward voltage ratings?

A: The LTE-3271B operates at 1.25V typical forward voltage compared to 1.3V for the SIR-341ST3FF. This 0.05V difference affects current-limiting resistor calculations. Circuits designed for the SIR-341ST3FF must be re-evaluated to ensure proper current limiting and optical output when using the LTE-3271B.

Q: Does the higher maximum forward current of the LTE-3271B (100mA vs. 75mA) affect substitution?

A: The higher current rating of the LTE-3271B provides design flexibility but does not automatically qualify it as a substitute. The circuit must be designed to operate within the LTE-3271B's specifications. Operating the LTE-3271B at 75mA (the original design point) is within its ratings and is permissible.

Q: Are there compliance or certification differences between these parts?

A: Both parts are ROHS3 compliant and carry identical ECCN (EAR99) and HTSUS (8541.41.0000) classifications. No compliance barriers exist for substitution from a regulatory standpoint.

Q: How do the radiant intensity specifications compare?

A: The SIR-341ST3FF specifies 5.6mW/sr @ 50mA, while the LTE-3271B specifies 6mW/sr @ 20mA. These measurements are taken at different forward currents, making direct comparison difficult. Circuit-level optical performance testing is required to confirm adequate signal detection with the substitute part.