IRFU3709ZPBF N-Channel MOSFET 30V 86A Equivalent & Substitute Parts

Part Overview

The IRFU3709ZPBF is an N-Channel MOSFET manufactured by Infineon Technologies, rated for 30V drain-to-source voltage with 86A continuous drain current at 25°C. This device is packaged in IPAK (TO-251AA) through-hole configuration and is part of the HEXFET® series. The IRFU3709ZPBF is classified as Obsolete, making identification of equivalent substitute parts necessary for ongoing production and maintenance applications. Substitute parts must maintain electrical and mechanical compatibility within the specified parameter ranges.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	30	V
Continuous Drain Current (Id) @ 25°C	86	A (Tc)
On-State Resistance (Rds On Max) @ 15A, 10V	6.5	mOhm
Gate Threshold Voltage (Vgs(th) Max) @ 250µA	2.25	V
Gate Charge (Qg Max) @ 4.5V	26	nC
Input Capacitance (Ciss Max) @ 15V	2330	pF
Power Dissipation (Max)	79	W (Tc)
Operating Temperature Range	-55 to 175	°C (TJ)
Package Type	IPAK (TO-251AA)	Through Hole
FET Type	N-Channel	—
Technology	MOSFET (Metal Oxide)	—

Substitute Part Grouping Explanation

Substitution of the IRFU3709ZPBF is determined by strict adherence to the following electrical and mechanical parameters:

Critical Compatibility Parameters:

Drain to Source Voltage (Vdss): Must equal or exceed 30V
Package Type: Must be IPAK (TO-251AA) through-hole configuration
FET Type: Must be N-Channel
Technology: Must be MOSFET (Metal Oxide)
Operating Temperature Range: Must support -55°C to 175°C (TJ)

Performance Parameters for Substitution:

Continuous Drain Current (Id): Substitute must meet or exceed 86A at 25°C
On-State Resistance (Rds On): Lower or equal values indicate improved performance
Gate Charge (Qg): Lower values reduce switching losses
Input Capacitance (Ciss): Lower values reduce gate drive requirements
Power Dissipation: Higher ratings provide thermal margin

The IRLU8743PBF qualifies as a substitute based on matching all critical compatibility parameters while providing enhanced electrical performance characteristics.

Parameter Comparison

Parameter	IRFU3709ZPBF	IRLU8743PBF	Unit
Manufacturer	Infineon Technologies	Infineon Technologies	—
FET Type	N-Channel	N-Channel	—
Technology	MOSFET (Metal Oxide)	MOSFET (Metal Oxide)	—
Drain to Source Voltage (Vdss)	30	30	V
Continuous Drain Current (Id) @ 25°C	86	160	A (Tc)
Rds On (Max) @ Vgs 10V	6.5 @ 15A	3.1 @ 25A	mOhm
Gate Threshold Voltage (Vgs(th) Max)	2.25 @ 250µA	2.35 @ 100µA	V
Gate Charge (Qg Max) @ 4.5V	26	59	nC
Input Capacitance (Ciss Max) @ 15V	2330	4880	pF
Power Dissipation (Max)	79	135	W (Tc)
Operating Temperature Range	-55 to 175	-55 to 175	°C (TJ)
Package Type	IPAK (TO-251AA)	IPAK (TO-251AA)	Through Hole
Series	HEXFET®	HEXFET®	—

Engineering Selection Recommendations

IRFU3709ZPBF Status: Obsolete. This part is no longer recommended for new designs and may face supply constraints.

IRLU8743PBF Suitability: The IRLU8743PBF is classified as Not For New Designs but remains available in inventory (2000 pcs). This substitute maintains identical voltage rating (30V Vdss) and package configuration (IPAK TO-251AA through-hole), ensuring mechanical and electrical compatibility.

Performance Advantages of IRLU8743PBF:

Continuous drain current increased from 86A to 160A, providing 86% higher current capacity
On-state resistance reduced from 6.5mOhm to 3.1mOhm, reducing conduction losses
Power dissipation increased from 79W to 135W, providing enhanced thermal headroom
Operating temperature range identical (-55°C to 175°C)

Compliance Considerations:

IRLU8743PBF: RoHS3 Compliant, REACH Unaffected, EAR99 classification
IRFU3709ZPBF: REACH Unaffected, EAR99 classification
Both devices: Moisture Sensitivity Level 1 (Unlimited)

For applications requiring the IRFU3709ZPBF, the IRLU8743PBF provides direct substitution with superior electrical performance and thermal characteristics within the same physical footprint.

Frequently Asked Questions (FAQ)

Q: Can IRLU8743PBF directly replace IRFU3709ZPBF in existing circuit boards?

A: Yes. Both devices use identical IPAK (TO-251AA) through-hole packaging with the same pin configuration and lead spacing. No PCB modifications are required.

Q: What are the key electrical differences between these parts?

A: The IRLU8743PBF provides higher continuous drain current (160A vs. 86A), lower on-state resistance (3.1mOhm vs. 6.5mOhm), and greater power dissipation capability (135W vs. 79W). Both maintain the same 30V voltage rating and operating temperature range.

Q: Why is gate charge higher in the IRLU8743PBF?

A: Gate charge (Qg) increases with die size and current capacity. The IRLU8743PBF's higher current rating (160A) results in increased gate charge (59nC vs. 26nC). Gate drive circuits must supply sufficient current to charge the gate within the required switching time.

Q: Are there any thermal considerations when substituting?

A: The IRLU8743PBF has higher power dissipation capability (135W vs. 79W), which typically indicates a larger die. In applications where the original part operated near thermal limits, the substitute may provide improved thermal margin. Verify that gate drive voltage and current specifications remain compatible with existing circuitry.

Q: What is the difference between product status "Obsolete" and "Not For New Designs"?

A: Obsolete indicates the IRFU3709ZPBF is no longer manufactured and supply is limited. Not For New Designs indicates the IRLU8743PBF remains available but Infineon does not recommend it for new circuit development. For maintenance and replacement applications, the IRLU8743PBF is suitable.

Q: Are both parts RoHS compliant?

A: The IRLU8743PBF is RoHS3 Compliant. The IRFU3709ZPBF RoHS status is not specified in the provided data. Both are REACH Unaffected and classified as EAR99.

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