FOD270L Equivalent & Substitute Parts

Part Overview

The FOD270L is an optoisolator with Darlington output and base connection, manufactured by onsemi. It provides 5000Vrms isolation voltage in a single-channel 8-DIP package. The part is classified as obsolete, making equivalent substitutes necessary for new designs and ongoing production support. Substitute parts must maintain compatibility across isolation voltage, output type, package configuration, and electrical performance parameters.

Key Parameters

Parameter	FOD270L
Manufacturer	onsemi
Product Status	Obsolete
Number of Channels	1
Voltage - Isolation	5000Vrms
Output Type	Darlington with Base
Voltage - Output (Max)	7V
Current - Output / Channel	60mA
Package / Case	8-DIP (0.300", 7.62mm)
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole

Substitute Part Grouping Explanation

Substitution eligibility for the FOD270L is determined by the following critical parameters:

Isolation Voltage: Minimum 5000Vrms required
Output Type: Darlington with Base configuration
Package: 8-DIP (0.300", 7.62mm) through-hole mounting
Number of Channels: Single channel
Output Current Capability: Minimum 60mA per channel
Maximum Output Voltage: Minimum 7V

The following parts meet these substitution criteria:

6N138 (Fairchild Semiconductor): Matches isolation voltage, output type, package, and current rating
6N139-020E (Broadcom Limited): Exceeds isolation voltage and output voltage specifications; active product status
HCPL-270L (Broadcom Limited): Reduced isolation voltage (3750Vrms); does not meet 5000Vrms requirement; included for reference only

Parameter Comparison

Parameter	FOD270L	6N138	6N139-020E	HCPL-270L
Manufacturer	onsemi	Fairchild Semiconductor	Broadcom Limited	Broadcom Limited
Product Status	Obsolete	Obsolete	Active	Active
Number of Channels	1	1	1	1
Voltage - Isolation	5000Vrms	5000Vrms	5000Vrms	3750Vrms
Current Transfer Ratio (Min)	400% @ 500µA	300% @ 1.6mA	500% @ 1.6mA	300% @ 1.6mA
Turn On / Turn Off Time (Typ)	3µs, 50µs	1.35µs, 7.6µs	200ns, 2µs	25µs, 50µs
Output Type	Darlington with Base	Darlington with Base	Darlington with Base	Darlington
Voltage - Output (Max)	7V	7V	18V	7V
Current - Output / Channel	60mA	60mA	60mA	60mA
Voltage - Forward (Vf) (Typ)	1.35V	1.4V	1.4V	1.5V
Operating Temperature	-40°C ~ 85°C	-55°C ~ 100°C	-40°C ~ 85°C	0°C ~ 70°C
Package / Case	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)	8-DIP (0.300", 7.62mm)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
RoHS Status	Not specified	RoHS non-compliant	ROHS3 Compliant	RoHS non-compliant

Engineering Selection Recommendations

Primary Substitute: 6N139-020E

The 6N139-020E is the recommended substitute for new designs. It maintains the required 5000Vrms isolation voltage and 8-DIP package configuration. The part has active product status, ensuring long-term availability. It exceeds the FOD270L in maximum output voltage (18V vs. 7V) and offers faster switching performance (200ns turn-on vs. 3µs). ROHS3 compliance supports modern manufacturing and environmental requirements.

Secondary Substitute: 6N138

The 6N138 provides direct electrical equivalence to the FOD270L with matching isolation voltage, output type, and package. However, it shares obsolete product status with the original part. Extended operating temperature range (-55°C to 100°C) provides additional margin for demanding applications. This option is suitable for legacy system maintenance where active product status is not required.

Not Recommended: HCPL-270L

The HCPL-270L does not meet the 5000Vrms isolation voltage requirement, providing only 3750Vrms. It is unsuitable as a direct substitute for applications requiring full 5000Vrms isolation. Additionally, the operating temperature range (0°C to 70°C) is narrower than the FOD270L specification.

Frequently Asked Questions (FAQ)

Q: Can the 6N139-020E replace the FOD270L in all applications?

A: The 6N139-020E meets all critical substitution parameters: 5000Vrms isolation, Darlington with Base output, 8-DIP package, and 60mA output current. The higher maximum output voltage (18V vs. 7V) and faster switching times are compatible with FOD270L circuit designs. Verify circuit-specific requirements before implementation.

Q: Why is the HCPL-270L listed if it cannot substitute the FOD270L?

A: The HCPL-270L is included for reference because it shares the same base product family and package. However, its 3750Vrms isolation voltage does not meet the 5000Vrms requirement of the FOD270L. It is not a valid substitute for applications requiring full isolation voltage specification.

Q: What is the difference between "Darlington with Base" and "Darlington" output types?

A: Darlington with Base provides an accessible base terminal for circuit control, allowing direct base current injection. Standard Darlington output does not expose the base connection. The FOD270L requires Darlington with Base configuration; substitutes must maintain this output type.

Q: Are all substitute parts available in the same packaging format?

A: Yes. All listed substitutes use 8-DIP (0.300", 7.62mm) through-hole packaging, matching the FOD270L footprint and mounting requirements. No PCB layout modifications are necessary for package compatibility.

Q: Does product status affect electrical performance?

A: Product status (Active vs. Obsolete) does not affect electrical performance. It indicates manufacturing availability and long-term supply reliability. Active products like the 6N139-020E provide assured future availability, while obsolete products may face supply constraints.

Q: What compliance certifications should I consider for new designs?

A: The 6N139-020E is ROHS3 compliant, meeting modern environmental and manufacturing standards. The 6N138 and HCPL-270L are RoHS non-compliant. For new product development, ROHS3 compliance is recommended to ensure regulatory alignment and supply chain compatibility.

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