FODM2701A Equivalent & Substitute Parts

Part Overview

The FODM2701A is a 3750Vrms optoisolator with transistor output manufactured by onsemi in a 4-SMD surface mount package. This component provides galvanic isolation for single-channel DC input applications with a maximum output voltage of 40V and 80mA output current capability. The part is currently obsolete, making equivalent substitutes necessary for ongoing production and maintenance applications.

Key Parameters

Parameter	Value
Manufacturer Part Number	FODM2701A
Manufacturer	onsemi
Category	Optoisolators
Number of Channels	1
Voltage - Isolation	3750Vrms
Current Transfer Ratio (Min)	50% @ 5mA
Current Transfer Ratio (Max)	300% @ 5mA
Output Type	Transistor
Voltage - Output (Max)	40V
Current - Output / Channel	80mA
Vce Saturation (Max)	300mV
Operating Temperature	-40°C ~ 110°C
Mounting Type	Surface Mount
Package / Case	4-SMD, Gull Wing
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility for the FODM2701A is determined by the following critical parameters:

Voltage isolation rating of 3750Vrms (mandatory match)
Single channel configuration
Transistor output type
DC input type
Surface mount package with 4-pin gull wing configuration
Maximum output voltage of 40V or greater
Output current capability of 80mA or greater
Current transfer ratio minimum of 50% @ 5mA or greater

Substitute parts are grouped into two categories based on these criteria:

Direct Equivalents: Parts meeting all critical parameters with identical or superior electrical specifications and active product status.

Functional Alternatives: Parts meeting core isolation and output requirements but with variations in secondary parameters such as output voltage rating, current transfer ratio range, or saturation voltage.

Parameter Comparison

Parameter	FODM2701A	FODM2701R2	FODM121A	PS2701-1-F3-A	LTV-357T	LTV-357T-B	PC451J00000F
Manufacturer	onsemi	onsemi	onsemi	Renesas	Lite-On	Lite-On	SHARP/Socle
Product Status	Obsolete	Active	Active	Not For New Designs	Active	Active	Active
Voltage - Isolation	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms
Number of Channels	1	1	1	1	1	1	1
Current Transfer Ratio (Min)	50% @ 5mA	50% @ 5mA	100% @ 5mA	50% @ 5mA	50% @ 5mA	130% @ 5mA	40% @ 5mA
Current Transfer Ratio (Max)	300% @ 5mA	300% @ 5mA	300% @ 5mA	300% @ 5mA	600% @ 5mA	260% @ 5mA	Not Specified
Output Type	Transistor	Transistor	Transistor	Transistor	Transistor	Transistor	Transistor
Voltage - Output (Max)	40V	40V	80V	40V	35V	35V	350V
Current - Output / Channel	80mA	80mA	80mA	80mA	50mA	50mA	50mA
Vce Saturation (Max)	300mV	300mV	400mV	300mV	200mV	200mV	300mV
Rise / Fall Time (Typ)	3µs, 3µs	3µs, 3µs	3µs, 3µs	3µs, 5µs	4µs, 3µs	4µs, 3µs	4µs, 5µs
Operating Temperature	-40°C ~ 110°C	-40°C ~ 110°C	-40°C ~ 110°C	-55°C ~ 100°C	-55°C ~ 110°C	-55°C ~ 110°C	-25°C ~ 100°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	4-SMD, Gull Wing	4-SMD, Gull Wing	4-SMD, Gull Wing	4-SOP	4-SOP	4-SOP	4-Mini-Flat
RoHS Status	Not Specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	RoHS Compliant

Engineering Selection Recommendations

Primary Recommendation: FODM2701R2

The FODM2701R2 is the direct equivalent replacement for the obsolete FODM2701A. Both parts share identical electrical specifications including 40V maximum output voltage, 80mA output current, 300mV maximum saturation voltage, and 3µs rise/fall times. The FODM2701R2 is currently active and available in Cut Tape and Digi-Reel packaging. RoHS3 compliance provides regulatory alignment for new designs.

Secondary Recommendation: FODM121A

The FODM121A offers superior current transfer ratio performance (100% minimum vs. 50% minimum) and higher maximum output voltage (80V vs. 40V) while maintaining identical isolation voltage and output current capability. This part is active and RoHS3 compliant. Selection is appropriate when higher output voltage headroom is required.

Alternative Recommendation: PS2701-1-F3-A

The PS2701-1-F3-A from Renesas matches the FODM2701A electrical specifications exactly, including 40V output voltage and 80mA output current. However, this part carries "Not For New Designs" status, limiting its use to legacy system maintenance and repair applications only.

Limited Compatibility: LTV-357T and LTV-357T-B

The Lite-On LTV-357T series provides 3750Vrms isolation and transistor output but with reduced output current (50mA vs. 80mA) and lower maximum output voltage (35V vs. 40V). These parts are suitable only for applications with lower current requirements. LTV-357T-B offers tighter current transfer ratio specification (130-260% vs. 50-300%).

Not Recommended: PC451J00000F

The PC451J00000F from SHARP/Socle Technology has a current transfer ratio minimum of 40%, below the FODM2701A specification of 50%. Additionally, the operating temperature range (-25°C to 100°C) is narrower than the original part. This part is suitable only for applications with relaxed performance requirements.

Frequently Asked Questions (FAQ)

Q: Can FODM2701R2 be used as a direct drop-in replacement for FODM2701A?

A: Yes. The FODM2701R2 is electrically and mechanically identical to the FODM2701A. Both use 4-SMD gull wing packaging and share all critical electrical parameters. The primary difference is product status: FODM2701R2 is active while FODM2701A is obsolete.

Q: What is the difference between FODM2701R2 and FODM121A?

A: Both are onsemi optoisolators with 3750Vrms isolation. The FODM121A has a higher minimum current transfer ratio (100% vs. 50%) and higher maximum output voltage (80V vs. 40V). The FODM2701R2 maintains the original FODM2701A specifications exactly. Selection depends on whether the application requires the enhanced specifications of FODM121A.

Q: Why is PS2701-1-F3-A marked "Not For New Designs"?

A: The PS2701-1-F3-A carries this status from Renesas, indicating the manufacturer is discontinuing this product line. While electrically compatible with FODM2701A, this part should be used only for maintenance of existing systems, not for new product development.

Q: Can LTV-357T replace FODM2701A in all applications?

A: No. The LTV-357T has reduced output current capability (50mA vs. 80mA) and lower maximum output voltage (35V vs. 40V). It is suitable only for applications with lower current and voltage requirements. Verify your circuit design can operate within these reduced specifications before substitution.

Q: What packaging differences exist among the substitute parts?

A: FODM2701A, FODM2701R2, and FODM121A use 4-SMD gull wing packages. PS2701-1-F3-A, LTV-357T, and LTV-357T-B use 4-SOP packages. PC451J00000F uses 4-Mini-Flat packaging. While all are surface mount, physical footprints differ. Verify PCB layout compatibility before selection.

Q: Are all substitute parts RoHS compliant?

A: FODM2701R2, FODM121A, PS2701-1-F3-A, LTV-357T, and LTV-357T-B are ROHS3 compliant. PC451J00000F is RoHS compliant. The original FODM2701A compliance status is not specified. For new designs, select from the RoHS-compliant alternatives.

Q: Which substitute has the fastest switching speed?

A: FODM2701A and FODM2701R2 both specify 3µs rise and fall times. LTV-357T and LTV-357T-B specify 4µs rise time with 3µs fall time. PC451J00000F specifies 4µs rise and 5µs fall times. For applications requiring the fastest switching, FODM2701R2 is the optimal choice.

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