4N373SD Optoisolator Equivalent & Substitute Parts

Part Overview

The 4N373SD is an optoisolator transistor with base output manufactured by onsemi, rated for 5300Vrms isolation voltage in a 6-SMD surface mount package. This component is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The 4N373SD provides DC input with transistor output including base connection, suitable for high-voltage isolation applications requiring galvanic separation.

Substiute Parts

4N373SD

onsemiIn Stock: 10604N373SD Datasheet

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4N37SR2VM

onsemiIn Stock: 29804N37SR2VM Datasheet

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4N37-X009

Vishay Semiconductor Opto DivisionIn Stock: 22444N37-X009 Datasheet

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4N37S

onsemiIn Stock: 32304N37S Datasheet

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4N37S-TA

Lite-On Inc.In Stock: 34104N37S-TA Datasheet

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4N37S-TA1

Lite-On Inc.In Stock: 220534N37S-TA1 Datasheet

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4N37SM

onsemiIn Stock: 127594N37SM Datasheet

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4N37SMT&R

Isocom Components 2004 LTDIn Stock: 8614N37SMT&R Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the 4N373SD is determined by the following critical parameters:

• Isolation Voltage: Minimum 5300Vrms or equivalent rating
• Output Configuration: Transistor with base output required
• Number of Channels: Single channel (1 channel)
• Input Type: DC input
• Package Type: 6-SMD, Gull Wing surface mount
• Current Transfer Ratio: Minimum 100% @ 10mA
• Operating Temperature Range: Must support -55°C to 100°C or equivalent
• Mounting Type: Surface mount only

Substitute parts are grouped into two categories based on isolation voltage compatibility:

Group 1 - High Isolation Voltage (≥5000Vrms): Parts maintaining isolation voltage at or above the 4N373SD specification, suitable for direct replacement in high-voltage isolation applications.

Group 2 - Lower Isolation Voltage (1500Vrms - 4170Vrms): Parts with reduced isolation voltage ratings, applicable only where circuit design permits lower isolation specifications.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitutes (Recommended for Direct Replacement)

The 4N37-X009 (Vishay Semiconductor Opto Division) is the preferred substitute, maintaining 5000Vrms isolation voltage within 94% of the original 4N373SD specification. This part is active status with RoHS3 compliance and supports the full -55°C to 100°C operating temperature range. The extended turn-on/turn-off time of 10µs versus 2µs must be evaluated against circuit timing requirements.

The 4N37S (onsemi) provides identical electrical characteristics to the 4N373SD with matching 5300Vrms isolation and 2µs switching times. However, this part is also obsolete status, offering no long-term supply advantage.

Secondary Substitutes (Conditional Replacement)

The 4N37SR2VM and 4N37SM (both onsemi) are active-status alternatives with 4170Vrms isolation voltage. These parts are suitable where circuit design permits reduced isolation voltage. Both maintain 2µs switching performance and support the required temperature range. The 4N37SR2VM is available in Tape & Reel packaging; the 4N37SM is supplied in Tube format.

Not Recommended for Direct Replacement

The 4N37S-TA and 4N37S-TA1 (Lite-On Inc.) feature 1500Vrms isolation voltage, representing a 72% reduction from the 4N373SD specification. These parts are suitable only for applications where isolation voltage requirements are significantly lower than the original design.

The 4N37SMT&R (Isocom Components 2004 LTD) specifies 7.5Vpk isolation, which is incompatible with the 4N373SD's high-voltage isolation requirement.

Frequently Asked Questions (FAQ)

Q: Can the 4N37SR2VM replace the 4N373SD directly?

A: The 4N37SR2VM is electrically compatible in terms of output configuration, switching speed, and package type. However, the isolation voltage is reduced from 5300Vrms to 4170Vrms. Substitution is valid only if circuit design permits this lower isolation rating. Verify isolation voltage requirements in your application before selection.

Q: What is the difference between 4N37S and 4N373SD?

A: The 4N37S and 4N373SD are electrically identical, both rated at 5300Vrms isolation with 2µs switching times and 100 mA forward current. Both are obsolete status. The primary difference is packaging designation. Neither offers supply continuity advantages.

Q: Why does the 4N37-X009 have longer switching times?

A: The 4N37-X009 specifies 10µs turn-on and turn-off times compared to the 4N373SD's 2µs. This is a characteristic difference between the Vishay and onsemi designs. Evaluate circuit timing margins to determine if this extended switching time is acceptable for your application.

Q: Are all substitute parts RoHS compliant?

A: The 4N37SR2VM, 4N37-X009, 4N37SM, and 4N37SMT&R are RoHS3 compliant. The 4N37S and 4N37S-TA1 are RoHS3 compliant. The 4N37S-TA compliance status is not specified in available data. Verify RoHS compliance requirements for your application and supply chain.

Q: What packaging options are available?

A: The 4N373SD is supplied in Tube format. Active substitutes are available in both Tape & Reel (4N37SR2VM, 4N37S-TA, 4N37S-TA1, 4N37SMT&R) and Tube (4N37-X009, 4N37SM) packaging. Confirm packaging compatibility with your assembly process.

Q: Can I use 4N37S-TA or 4N37S-TA1 in place of the 4N373SD?

A: These parts share the same 6-SMD package and DC input with transistor base output. However, the 1500Vrms isolation voltage is significantly lower than the 4N373SD's 5300Vrms rating. Substitution is valid only for applications where isolation voltage requirements are substantially reduced from the original design specification.