4N28TM Optoisolator Equivalent & Substitute Parts

Part Overview

The 4N28TM is an optoisolator transistor with base output manufactured by onsemi, designed for high-voltage isolation applications. This component features a 4170Vrms isolation rating and single-channel transistor output in a 6-DIP package. The 4N28TM is currently classified as obsolete, making identification of equivalent and substitute parts essential for ongoing design support and procurement planning.

Key Parameters

Parameter	Value
Manufacturer Part Number	4N28TM
Manufacturer	onsemi
Category	Optoisolators
Number of Channels	1
Voltage - Isolation	4170Vrms
Current Transfer Ratio (Min)	10% @ 10mA
Output Type	Transistor with Base
Voltage - Output (Max)	30V
Voltage - Forward (Vf) (Typ)	1.18V
Current - DC Forward (If) (Max)	60 mA
Vce Saturation (Max)	500mV
Operating Temperature	-40°C ~ 100°C
Package / Case	6-DIP (0.400", 10.16mm)
Mounting Type	Through Hole
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility for the 4N28TM is determined by the following critical parameters:

Isolation Voltage: 4170Vrms minimum
Number of Channels: 1 channel
Output Type: Transistor with Base
Package Type: 6-DIP form factor
Mounting: Through Hole
Current Transfer Ratio: 10% @ 10mA minimum
Maximum Output Voltage: 30V
Maximum Forward Current: 60 mA
Vce Saturation: 500mV maximum

Parts meeting all these criteria are considered direct substitutes. Parts with variations in secondary parameters (such as operating temperature range, turn-on/turn-off time specifications, or packaging dimensions within the 6-DIP family) may be evaluated based on application requirements.

Parameter Comparison

Parameter	4N28TM	4N28TVM	4N28G	4N28M
Manufacturer	onsemi	onsemi	Isocom Components 2004 LTD	onsemi
Number of Channels	1	1	1	1
Voltage - Isolation	4170Vrms	4170Vrms	7.5Vpk	4170Vrms
Current Transfer Ratio (Min)	10% @ 10mA	10% @ 10mA	10% @ 10mA	10% @ 10mA
Output Type	Transistor with Base	Transistor with Base	Transistor with Base	Transistor with Base
Voltage - Output (Max)	30V	30V	30V	30V
Voltage - Forward (Vf) (Typ)	1.18V	1.18V	1.2V	1.18V
Current - DC Forward (If) (Max)	60 mA	60 mA	60 mA	60 mA
Vce Saturation (Max)	500mV	500mV	500mV	500mV
Operating Temperature	-40°C ~ 100°C	-40°C ~ 100°C	-55°C ~ 100°C	-40°C ~ 100°C
Package / Case	6-DIP (0.400", 10.16mm)	6-DIP (0.400", 10.16mm)	6-DIP (0.400", 10.16mm)	6-DIP (0.300", 7.62mm)
Product Status	Obsolete	Last Time Buy	Active	Active

Engineering Selection Recommendations

4N28TVM (onsemi): This part maintains identical electrical specifications to the 4N28TM with matching isolation voltage (4170Vrms), output characteristics, and package dimensions. The 4N28TVM is classified as Last Time Buy, indicating limited availability. Selection of this part is appropriate for applications requiring exact electrical equivalence with the original 4N28TM design.

4N28M (onsemi): This part provides full electrical equivalence to the 4N28TM across all critical parameters. The 4N28M is classified as Active and offers the highest availability (22,302 units in stock). The primary difference is the package dimension (0.300" vs. 0.400" DIP spacing), which may require PCB layout verification. This part is recommended for new procurement when board layout accommodates the tighter DIP spacing.

4N28G (Isocom Components 2004 LTD): This part meets the core functional requirements with matching channel count, output type, and package form factor. However, the isolation voltage specification (7.5Vpk) is significantly lower than the 4N28TM (4170Vrms). The 4N28G is classified as Active with good availability. Selection of this part is restricted to applications where the lower isolation voltage is acceptable and does not compromise system safety or performance requirements.

Frequently Asked Questions (FAQ)

Q: Can the 4N28TVM be used as a direct replacement for the 4N28TM?

A: Yes. The 4N28TVM maintains identical electrical specifications including isolation voltage (4170Vrms), current transfer ratio, output voltage, and package dimensions (6-DIP 0.400"). The primary consideration is availability, as the 4N28TVM is classified as Last Time Buy.

Q: What is the key difference between the 4N28M and 4N28TM?

A: The 4N28M is electrically equivalent to the 4N28TM across all critical parameters. The difference is in DIP package spacing: the 4N28M uses 0.300" spacing while the 4N28TM uses 0.400" spacing. PCB layout compatibility must be verified before selection.

Q: Is the 4N28G a suitable substitute for high-voltage isolation applications?

A: The 4N28G is not suitable for applications requiring 4170Vrms isolation. The 4N28G isolation rating is 7.5Vpk, which is substantially lower. The 4N28G may only be selected for applications with lower isolation voltage requirements.

Q: What packaging considerations apply to these substitutes?

A: All parts use 6-DIP through-hole mounting. The 4N28TM and 4N28TVM use 0.400" DIP spacing, while the 4N28M uses 0.300" DIP spacing. The 4N28G uses standard 0.400" spacing. PCB footprint compatibility must be confirmed before part selection.

Q: Which substitute offers the best availability?

A: The 4N28M (onsemi) offers the highest availability with 22,302 units in stock and Active product status. This part is recommended for new designs when package spacing is compatible with board layout.

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