CNW85SD Equivalent & Substitute Parts

Part Overview

The CNW85SD is an optoisolator transistor with base output manufactured by onsemi, designed for DC input applications requiring galvanic isolation up to 5900Vrms. This component features a single channel configuration in a 6-SMD surface mount package with a maximum output voltage of 80V and 100mA output current capability. The CNW85SD is classified as obsolete, making identification of functionally compatible substitute components essential for ongoing system support and new design implementations.

Substiute Parts

CNW85SD

onsemiIn Stock: 863CNW85SD Datasheet

Current PartRFQ

CNY171SM

Fairchild SemiconductorIn Stock: 2598CNY171SM Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the CNW85SD is determined by the following critical parameters that must remain compatible:

• Isolation Voltage: The substitute must support the required isolation voltage specification. The CNW85SD specifies 5900Vrms isolation.
• Output Configuration: The substitute must provide transistor output with base connection to maintain circuit interface compatibility.
• Single Channel Architecture: The substitute must be a single-channel device matching the original configuration.
• Package Type: The substitute must use 6-SMD, Gull Wing surface mount packaging for PCB compatibility.
• Output Voltage and Current Ratings: The substitute must support the maximum output voltage (80V) and output current (100mA) requirements.
• Input Type: The substitute must accept DC input signals.
• Vce Saturation: The substitute must meet or exceed the saturation voltage specification of 400mV maximum.

The CNY171SM qualifies as a substitute based on matching these core parameters, though with notable differences in Current Transfer Ratio performance and isolation voltage rating.

Parameter Comparison

Engineering Selection Recommendations

The CNY171SM is available as an active product from Fairchild Semiconductor, providing supply continuity for applications previously using the obsolete CNW85SD. Selection of the CNY171SM requires evaluation of the following factors based on provided specifications:

Isolation Voltage Consideration: The CNY171SM provides 4170Vrms isolation compared to the CNW85SD specification of 5900Vrms. Applications requiring the full 5900Vrms isolation rating cannot use this substitute without additional isolation measures.

Output Current Rating: The CNY171SM is rated for 50mA maximum output current per channel, compared to the CNW85SD rating of 100mA. Circuits designed for 100mA output current operation require redesign or alternative substitutes.

Output Voltage Rating: The CNY171SM supports 70V maximum output voltage versus the CNW85SD specification of 80V. Applications operating near the 80V limit require circuit verification.

Current Transfer Ratio: The CNY171SM exhibits significantly higher current transfer ratio (40-80% @ 10mA) compared to the CNW85SD (0.63-3.20% @ 10mA). This difference affects input drive requirements and circuit biasing calculations.

Compliance Status: The CNY171SM status as an active product ensures ongoing availability and manufacturing consistency. The CNW85SD obsolete status necessitates substitution planning for production continuity.

Frequently Asked Questions (FAQ)

Q: Can the CNY171SM directly replace the CNW85SD in existing designs?

A: Direct replacement is possible only if the application operates within the CNY171SM electrical ratings. The lower isolation voltage (4170Vrms vs. 5900Vrms), reduced output current (50mA vs. 100mA), and lower output voltage (70V vs. 80V) must be verified against circuit requirements. The significantly higher current transfer ratio also affects input drive circuit design.

Q: What is the impact of the different Current Transfer Ratio specifications?

A: The CNY171SM current transfer ratio of 40-80% @ 10mA is substantially higher than the CNW85SD specification of 0.63-3.20% @ 10mA. This means the CNY171SM requires less input current to achieve the same output current, potentially reducing input drive circuit complexity. However, circuits designed specifically for the CNW85SD's lower CTR may require input current adjustment.

Q: Are the 6-SMD packages physically identical?

A: Both components use 6-SMD, Gull Wing surface mount packaging, providing physical and footprint compatibility for PCB assembly. No layout modifications are required for package accommodation.

Q: What are the key electrical differences that affect substitution decisions?

A: The primary differences are isolation voltage rating (4170Vrms vs. 5900Vrms), maximum output current (50mA vs. 100mA), maximum output voltage (70V vs. 80V), and current transfer ratio performance. Applications must operate within all CNY171SM ratings simultaneously for successful substitution.

Q: Is the CNY171SM suitable for high-isolation applications?

A: The CNY171SM isolation rating of 4170Vrms is lower than the CNW85SD specification of 5900Vrms. Applications requiring isolation above 4170Vrms cannot use the CNY171SM without additional isolation components or alternative part selection.

Q: How does the operating temperature range affect substitution?

A: The CNY171SM specifies an operating temperature range of -40°C to 100°C. The CNW85SD operating temperature is not specified in available documentation. Verify that the CNY171SM temperature range meets application environmental requirements.