3N243TX Optoisolator - Equivalent & Substitute Parts

Part Overview

The 3N243TX is a 1000VDC isolation optoisolator with transistor output, designed for single-channel DC signal isolation applications. Manufactured by TT Electronics/Optek Technology in a TO-72-4 metal can package, this component provides galvanic isolation between input and output circuits with a 30mA output current capability.

The 3N243TX is classified as obsolete. Locating equivalent or substitute parts is necessary to support legacy system maintenance, redesigns, or when original inventory becomes unavailable. Active alternatives with compatible electrical and mechanical specifications are available from the same manufacturer.

Substiute Parts

3N243TX

TT Electronics / Optek TechnologyIn Stock: 8723N243TX Datasheet

Current PartRFQ

3N245TX

TT Electronics/Optek TechnologyIn Stock: 10333N245TX Datasheet

MFR RecommendedRFQ

3N243

TT Electronics/Optek TechnologyIn Stock: 8253N243 Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 3N243TX optoisolator are identified based on strict electrical and mechanical compatibility criteria:

Critical Parameters for Substitution:

• Voltage - Isolation: 1000VDC (must match)
• Number of Channels: 1 (must match)
• Output Type: Transistor (must match)
• Package / Case: TO-206AF, TO-72-4 Metal Can (must match)
• Mounting Type: Through Hole (must match)
• Voltage - Output (Max): 30V (must match)
• Current - Output / Channel: 30mA (must match)
• Operating Temperature: -55°C ~ 125°C (must match)
• Input Type: DC (must match)

Substitute Categories:

1. MFR Recommended Substitute (3N245TX): Active product with identical isolation voltage, channel count, output type, package, and thermal specifications. Differs in Current Transfer Ratio (60% @ 10mA vs. 15% @ 10mA) and RoHS compliance status.

2. Parametric Equivalent (3N243): Active product with identical electrical specifications including Current Transfer Ratio (15% @ 10mA), isolation voltage, output characteristics, and package configuration. Differs only in product status and RoHS compliance.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Parametric Equivalence): The 3N243 is the optimal substitute when exact electrical performance matching is required. It maintains the identical Current Transfer Ratio (15% @ 10mA) and all other electrical specifications of the 3N243TX. As an active product with ROHS3 compliance, it provides long-term availability and regulatory alignment for new designs or legacy system updates.

For Manufacturer-Recommended Substitution: The 3N245TX is the manufacturer-designated alternative. It provides higher Current Transfer Ratio performance (60% @ 10mA), which may improve circuit efficiency in applications where increased optical coupling gain is beneficial. This part is active and ROHS3 compliant. Selection of 3N245TX requires circuit validation to confirm that the higher current transfer ratio does not introduce unintended behavior in the receiving circuit.

Compliance Considerations: Both substitute parts (3N243 and 3N245TX) are ROHS3 compliant, whereas the original 3N243TX is RoHS non-compliant. For applications subject to RoHS regulations or environmental compliance requirements, either substitute part satisfies current regulatory standards. All three parts maintain REACH Unaffected status and identical MSL ratings.

Frequently Asked Questions (FAQ)

Q: Can the 3N245TX directly replace the 3N243TX in all applications? A: The 3N245TX is electrically compatible in terms of isolation voltage, output voltage/current ratings, package, and thermal range. However, the Current Transfer Ratio differs (60% vs. 15% @ 10mA). Circuit validation is necessary to confirm that the higher optical coupling gain does not cause unintended switching behavior or timing changes in the receiving circuit.

Q: What is the difference between the 3N243 and 3N245TX substitutes? A: The 3N243 maintains identical electrical specifications to the original 3N243TX, including Current Transfer Ratio (15% @ 10mA). The 3N245TX offers higher Current Transfer Ratio (60% @ 10mA). Both are active products with ROHS3 compliance. Selection depends on whether exact performance matching (3N243) or improved optical coupling gain (3N245TX) is required.

Q: Are all substitute parts available in the same package? A: Yes. The 3N243TX, 3N245TX, and 3N243 are all supplied in TO-206AF, TO-72-4 Metal Can packages with Through Hole mounting. Pin configuration and physical dimensions are identical, enabling direct socket replacement.

Q: Do the substitute parts meet current regulatory requirements? A: Both the 3N243 and 3N245TX are ROHS3 compliant, whereas the original 3N243TX is RoHS non-compliant. All three parts are REACH Unaffected. For applications requiring RoHS compliance, either substitute part is suitable.

Q: What is the inventory status of substitute parts? A: The 3N245TX has 980 pcs in stock, and the 3N243 has 798 pcs in stock. Both are active products with established supply chains, providing reliable availability for replacement and redesign applications.