FOD270LT Equivalent & Substitute Parts

Part Overview

The FOD270LT is an optoisolator with Darlington output and base connection, manufactured by onsemi. It provides 5000Vrms isolation with single-channel configuration in 8-DIP packaging. The part is classified as obsolete, making equivalent substitutes necessary for new designs and ongoing production support. Substitute parts must maintain electrical compatibility across isolation voltage, output type, current transfer ratio, and thermal operating range while accommodating packaging variations.

Substiute Parts

FOD270LT

onsemiIn Stock: 1051FOD270LT Datasheet

Current PartRFQ

6N138M

Fairchild SemiconductorIn Stock: 155116N138M Datasheet

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6N139-020E

Broadcom LimitedIn Stock: 10856N139-020E Datasheet

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6N139M

onsemiIn Stock: 211196N139M Datasheet

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HCNW138-000E

Broadcom LimitedIn Stock: 7703HCNW138-000E Datasheet

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HCNW139

Broadcom LimitedIn Stock: 1960HCNW139 Datasheet

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HCNW139-000E

Broadcom LimitedIn Stock: 18908HCNW139-000E Datasheet

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HCPL-270L

Broadcom LimitedIn Stock: 1089HCPL-270L Datasheet

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HCPL-270L-000E

Broadcom LimitedIn Stock: 6084HCPL-270L-000E Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility is determined by the following criteria applied strictly to the provided parameters:

Primary Compatibility Requirements:

• Voltage - Isolation: 5000Vrms (exact match required)
• Number of Channels: 1 (exact match required)
• Output Type: Darlington with Base or Darlington (compatible)
• Mounting Type: Through Hole (exact match required)
• Input Type: DC (exact match required)
• Current - Output / Channel: 60mA (exact match required)

Secondary Compatibility Considerations:

• Current Transfer Ratio: Minimum 300% acceptable; maximum values may vary
• Operating Temperature: -40°C minimum and 85°C maximum required
• Package / Case: 8-DIP acceptable with dimensional variations (0.300" or 0.400")
• Voltage - Output (Max): 7V or higher acceptable

Non-Compatible Parts (Excluded from Substitution):

• HCPL-270L and HCPL-270L-000E: Isolation voltage 3750Vrms (below 5000Vrms requirement)

Qualified Substitute Parts:

• 6N138M (Fairchild Semiconductor)
• 6N139-020E (Broadcom Limited)
• 6N139M (onsemi)
• HCNW138-000E (Broadcom Limited)
• HCNW139 (Broadcom Limited)
• HCNW139-000E (Broadcom Limited)

Parameter Comparison

Engineering Selection Recommendations

For Direct Pin-Compatible Replacement (Same PCB Layout):

Select from parts with matching package dimensions (0.400", 10.16mm): 6N138M, HCNW138-000E, HCNW139, or HCNW139-000E. These require no PCB modification and maintain identical lead spacing.

For Active Production Status Priority:

All qualified substitutes (6N138M, 6N139-020E, 6N139M, HCNW138-000E, HCNW139, HCNW139-000E) carry active product status, ensuring long-term availability and supply chain stability compared to the obsolete FOD270LT.

For RoHS3 Compliance Requirement:

Select 6N139-020E, 6N139M, HCNW138-000E, or HCNW139-000E. These parts meet ROHS3 compliance. HCNW139 is RoHS non-compliant and should be avoided in regulated applications.

For Extended Temperature Range:

6N139M supports -40°C to 100°C operating range, exceeding the FOD270LT specification of -40°C to 85°C. All other substitutes maintain the -40°C to 85°C range.

For Improved Switching Performance:

6N139-020E and 6N139M offer significantly faster switching times (200ns/2µs and 240ns/1.3µs respectively) compared to FOD270LT (3µs/50µs), beneficial for high-frequency applications.

For Higher Output Voltage Capability:

6N139-020E, 6N139M, HCNW139, and HCNW139-000E support 18V maximum output voltage, providing additional design margin over the 7V limit of FOD270LT and 6N138M.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part with a different package dimension (0.300" vs 0.400")?

A: Package dimension differences require PCB layout modification. Parts with 0.300" spacing (6N139-020E, 6N139M) have different lead pitch than the original 0.400" FOD270LT. Verify PCB hole spacing compatibility before selection. Direct socket replacement is not possible without redesign.

Q: What is the minimum current transfer ratio acceptable for substitution?

A: The FOD270LT specifies 400% minimum at 500µA. Qualified substitutes range from 200% to 500% minimum, measured at different test currents (1.6mA or 12mA). Lower CTR values require circuit design verification to ensure adequate output current under worst-case conditions.

Q: Are all substitute parts suitable for new designs?

A: Yes. All qualified substitutes carry active product status. HCNW139-000E, 6N139M, and 6N139-020E are recommended for new designs due to ROHS3 compliance and active manufacturer support. HCNW139 is RoHS non-compliant and should be avoided in regulated markets.

Q: How do switching times affect circuit performance?

A: FOD270LT switching times are 3µs (on) and 50µs (off). Faster substitutes like 6N139-020E (200ns/2µs) and 6N139M (240ns/1.3µs) enable higher-frequency operation. Slower substitutes like HCNW138-000E (11µs/70µs) and HCNW139 variants (11µs/11µs) may limit maximum switching frequency. Verify application frequency requirements against substitute specifications.

Q: What is the impact of different output voltage ratings?

A: FOD270LT and 6N138M are rated 7V maximum output. Substitutes rated 18V (6N139-020E, 6N139M, HCNW139, HCNW139-000E) provide higher voltage capability without functional impact on 7V circuits. Higher ratings offer design flexibility for future applications but do not affect compatibility with existing 7V designs.

Q: Is MSL (Moisture Sensitivity Level) important for my application?

A: MSL 1 (Unlimited) indicates no moisture sensitivity restrictions. FOD270LT, 6N139-020E, HCNW138-000E, HCNW139, and HCNW139-000E all carry MSL 1. 6N139M lists MSL as Not Applicable. Standard handling procedures apply to all qualified substitutes.

Q: Can I substitute HCPL-270L or HCPL-270L-000E for FOD270LT?

A: No. HCPL-270L and HCPL-270L-000E provide only 3750Vrms isolation, below the 5000Vrms requirement of FOD270LT. These parts are not electrically compatible and must not be used as substitutes.