4N33SD Optoisolator Equivalent & Substitute Parts

Part Overview

The 4N33SD is an optoisolator with Darlington output and base connection, manufactured by onsemi. This component provides 5300Vrms isolation in a 6-SMD surface mount package. The 4N33SD is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility across isolation voltage, output configuration, and electrical performance parameters.

Substiute Parts

4N33SD

onsemiIn Stock: 40804N33SD Datasheet

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4N33SR2M

onsemiIn Stock: 31544N33SR2M Datasheet

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4N33SM

onsemiIn Stock: 14404N33SM Datasheet

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4N33SMT&R

Isocom Components 2004 LTDIn Stock: 20324N33SMT&R Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 4N33SD is determined by the following critical parameters:

• Output Configuration: Darlington with Base output type
• Package Type: 6-SMD, Gull Wing surface mount
• Number of Channels: Single channel (1)
• Input Type: DC
• Maximum Output Voltage: 30V
• Maximum Output Current: 150mA minimum
• Isolation Voltage: Minimum 4170Vrms (acceptable reduction from 5300Vrms for active alternatives)
• Current Transfer Ratio: Minimum 500% @ 10mA
• Vce Saturation: Maximum 1V
• Moisture Sensitivity: MSL 1 (Unlimited)

The 4N33SD has three identified substitute parts within the 4N33 base product family. Two substitutes (4N33SR2M and 4N33SM) are active products from onsemi with reduced isolation voltage (4170Vrms) but identical output specifications. The third substitute (4N33SMT&R) is from Isocom Components with significantly lower isolation voltage (7.5Vpk) and reduced output current (50mA), limiting its applicability.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitutes (Recommended):

The 4N33SR2M and 4N33SM are the preferred substitutes for the obsolete 4N33SD. Both are active onsemi products with identical electrical output specifications (150mA output current, 500% CTR minimum, 1V Vce saturation). The isolation voltage reduction from 5300Vrms to 4170Vrms is acceptable for applications not requiring the full isolation rating of the original part. Both substitutes carry ROHS3 compliance certification. Selection between these two depends on packaging requirements: 4N33SR2M is supplied in Tape & Reel format for automated assembly, while 4N33SM is supplied in Tube packaging for manual handling.

Secondary Substitute (Limited Application):

The 4N33SMT&R from Isocom Components is an active product but has significant limitations. The maximum output current is reduced to 50mA (compared to 150mA for the primary substitutes), and the isolation voltage specification (7.5Vpk) is substantially lower. This part is suitable only for applications with reduced current requirements and lower isolation voltage demands. The operating temperature range matches the original part (-55°C ~ 100°C).

Compliance Considerations:

The 4N33SD does not specify RoHS status. Both onsemi substitutes (4N33SR2M and 4N33SM) are ROHS3 compliant, making them suitable for designs requiring RoHS compliance. All parts maintain MSL 1 (Unlimited) moisture sensitivity rating.

Frequently Asked Questions (FAQ)

Q: Can the 4N33SR2M or 4N33SM directly replace the 4N33SD?

A: Yes, both parts are direct functional replacements. They maintain identical output current (150mA), output voltage (30V maximum), Darlington with Base configuration, and current transfer ratio (500% minimum @ 10mA). The isolation voltage is reduced from 5300Vrms to 4170Vrms, which is acceptable for most applications. Both are active products from onsemi, ensuring long-term availability.

Q: What is the difference between 4N33SR2M and 4N33SM?

A: The electrical specifications are identical. The difference is packaging: 4N33SR2M is supplied in Tape & Reel (TR) format for automated pick-and-place assembly, while 4N33SM is supplied in Tube packaging for manual component handling. Select based on your assembly process requirements.

Q: Is the 4N33SMT&R a suitable replacement?

A: The 4N33SMT&R is a functional substitute only for applications with reduced current requirements. Its maximum output current is 50mA compared to 150mA for the primary substitutes. The isolation voltage specification (7.5Vpk) is also significantly lower. Use this part only if your circuit design can accommodate these reduced specifications.

Q: What are the key parameters that determine substitutability?

A: Substitutability is determined by: single-channel Darlington with Base output configuration, 6-SMD Gull Wing surface mount package, minimum 150mA output current capability, minimum 500% current transfer ratio, maximum 1V Vce saturation, and 30V maximum output voltage. Isolation voltage can be reduced from 5300Vrms to 4170Vrms for active alternatives without affecting output performance.

Q: Are there temperature range differences between substitutes?

A: Yes. The 4N33SD and 4N33SMT&R operate from -55°C to 100°C. The onsemi substitutes (4N33SR2M and 4N33SM) operate from -40°C to 100°C. If your application requires operation below -40°C, the 4N33SMT&R is the only substitute maintaining the full temperature range.

Q: Do all substitutes have the same moisture sensitivity rating?

A: Yes. All four parts (4N33SD, 4N33SR2M, 4N33SM, and 4N33SMT&R) have MSL 1 (Unlimited) moisture sensitivity level, indicating no moisture sensitivity restrictions for storage or handling.