MOC8021S Optoisolator Equivalent & Substitute Parts

Part Overview

The MOC8021S is a high-voltage isolation optoisolator with Darlington output manufactured by onsemi. This component provides 5300Vrms isolation in a 6-SMD surface mount package and is designed for applications requiring galvanic isolation with high current transfer capability. The MOC8021S is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Substiute Parts

MOC8021S

onsemiIn Stock: 890MOC8021S Datasheet

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MOC8021SM

onsemiIn Stock: 2066MOC8021SM Datasheet

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MOC8021SM

onsemiIn Stock: 2066MOC8021SM Datasheet

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MOC8021SMT&R

Isocom Components 2004 LTDIn Stock: 1197MOC8021SMT&R Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the MOC8021S is determined by the following critical parameters:

• Package compatibility: 6-SMD, Gull Wing surface mount form factor
• Isolation voltage: Minimum 4170Vrms (acceptable reduction from 5300Vrms for most applications)
• Output type: Darlington configuration
• Single channel: 1 channel requirement
• Output voltage rating: Minimum 35V (MOC8021S rated 50V)
• Output current: Minimum 150mA per channel
• Input type: DC input
• Operating temperature range: Must support -40°C minimum (MOC8021S supports -55°C)

Two substitute parts meet these criteria with varying degrees of parameter alignment:

MOC8021SM (onsemi): Active product with identical package, channel count, and output specifications. Isolation voltage reduced to 4170Vrms. Fully compatible for applications not requiring the full 5300Vrms isolation rating.

MOC8021SMT&R (Isocom Components 2004 LTD): Active product in Tape & Reel packaging. Shares 6-SMD package and Darlington output. Isolation voltage specification differs significantly (7.5Vpk). Output voltage maximum reduced to 35V. Suitable only for applications with lower isolation requirements.

Parameter Comparison

Engineering Selection Recommendations

MOC8021SM is the primary substitute for MOC8021S applications. Both parts are manufactured by onsemi with identical package geometry and output specifications. The MOC8021SM is an active product with ROHS3 compliance, ensuring long-term availability and regulatory alignment. The isolation voltage reduction from 5300Vrms to 4170Vrms is acceptable for applications where the full isolation rating of the original part is not a design requirement. The operating temperature range narrows from -55°C to -40°C minimum, which may require thermal design review for extreme cold environments.

MOC8021SMT&R is a secondary option suitable only for applications with significantly reduced isolation voltage requirements. The 7.5Vpk isolation specification represents a substantial departure from the MOC8021S rating and should be selected only when circuit isolation requirements are confirmed to be below this level. The reduced output voltage maximum (35V versus 50V) and narrower operating temperature range (-25°C to 100°C) further limit its applicability as a direct substitute.

Frequently Asked Questions (FAQ)

Q: Can MOC8021SM directly replace MOC8021S in existing designs?

A: MOC8021SM is compatible for applications where 4170Vrms isolation is sufficient. The package, channel count, output type, and maximum output voltage are identical. Designs requiring the full 5300Vrms isolation rating of the original part must evaluate whether the reduced isolation voltage meets circuit requirements.

Q: What is the primary difference between MOC8021SM and MOC8021SMT&R?

A: MOC8021SM maintains the 4170Vrms isolation specification and 50V output voltage rating of the onsemi product line. MOC8021SMT&R, manufactured by Isocom Components, has a significantly lower isolation voltage (7.5Vpk) and reduced output voltage maximum (35V). These differences make MOC8021SMT&R unsuitable as a general substitute unless isolation requirements are substantially lower.

Q: Does packaging format affect substitution eligibility?

A: All three parts use 6-SMD, Gull Wing surface mount packages, ensuring mechanical and footprint compatibility. MOC8021SM is supplied in bulk packaging, while MOC8021SMT&R is supplied in Tape & Reel format. Packaging format does not affect electrical compatibility but may influence procurement and assembly processes.

Q: Are there compliance or regulatory differences between the substitute parts?

A: MOC8021SM carries ROHS3 compliance certification. MOC8021SMT&R also carries ROHS3 compliance. Both parts are REACH Unaffected and classified as EAR99 for export control purposes. All three parts have MSL rating of 1 (Unlimited), indicating no moisture sensitivity restrictions.

Q: What operating temperature considerations apply to substitution?

A: MOC8021S operates from -55°C to 100°C. MOC8021SM operates from -40°C to 100°C, narrowing the low-temperature range by 15°C. MOC8021SMT&R operates from -25°C to 100°C, further restricting low-temperature operation. Applications requiring operation below -40°C must retain the original MOC8021S or identify alternative solutions.