IRFZ44Z N-Channel 55V 51A MOSFET Equivalent & Substitute Parts

Part Overview

The IRFZ44Z is an N-Channel MOSFET manufactured by Infineon Technologies, rated for 55V drain-to-source voltage and 51A continuous drain current in a TO-220AB through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for new designs and production continuity. The IRFZ44Z operates across a temperature range of -55°C to 175°C and dissipates up to 80W at the case temperature. Substitutes must maintain electrical compatibility within the specified voltage, current, and thermal parameters while accommodating packaging and compliance requirements.

Key Parameters

Parameter	Value	Unit
Drain-to-Source Voltage (Vdss)	55	V
Continuous Drain Current (Id) @ 25°C	51	A
On-State Resistance (Rds On) @ 31A, 10V	13.9	mOhm
Gate Threshold Voltage (Vgs(th)) @ 250µA	4	V
Gate Charge (Qg) @ 10V	43	nC
Power Dissipation (Max)	80	W
Operating Temperature Range	-55 to 175	°C
Package Type	TO-220AB	—
Mounting Type	Through Hole	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution eligibility is determined by the following criteria applied strictly to the provided parameters:

Primary Compatibility Criteria:

Drain-to-Source Voltage (Vdss): Must equal or exceed 55V
Continuous Drain Current (Id): Must equal or exceed 51A at 25°C
Gate Threshold Voltage (Vgs(th)): Must be compatible at 4V nominal specification
Gate Drive Voltage: Must operate at 10V nominal drive
Operating Temperature Range: Must span -55°C to 175°C minimum
Mounting Type: Through Hole configuration required
Package: TO-220 family (TO-220AB or TO-220-3 acceptable)

Secondary Considerations:

On-State Resistance (Rds On): Lower values indicate improved performance
Power Dissipation: Higher ratings provide thermal margin
Product Status: Active status preferred for long-term availability
RoHS Compliance: ROHS3 compliance preferred for regulatory alignment

Substitute parts are grouped into two categories: Direct Replacements (matching or exceeding all primary criteria with minimal parameter variance) and Enhanced Alternatives (exceeding primary criteria with improved electrical performance).

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ 25°C (A)	Rds On (mOhm)	Qg (nC)	Pd Max (W)	Status	Package
IRFZ44Z	Infineon	55	51	13.9 @ 31A, 10V	43 @ 10V	80	Obsolete	TO-220AB
HUF75332P3	onsemi	55	60	19 @ 60A, 10V	85 @ 20V	145	Active	TO-220-3
HUF75339P3	onsemi	55	75	12 @ 75A, 10V	130 @ 20V	200	Active	TO-220-3
HUF75344P3	onsemi	55	75	8 @ 75A, 10V	210 @ 20V	285	Active	TO-220-3
IRFZ44PBF	Vishay Siliconix	60	50	28 @ 31A, 10V	67 @ 10V	150	Active	TO-220AB
IRFZ44RPBF	Vishay Siliconix	60	50	28 @ 31A, 10V	67 @ 10V	150	Active	TO-220AB
PHP191NQ06LT,127	Nexperia USA Inc.	55	75	3.7 @ 25A, 10V	95.6 @ 5V	300	Obsolete	TO-220AB
PHP79NQ08LT,127	Nexperia USA Inc.	75	73	16 @ 25A, 10V	30 @ 5V	157	Obsolete	TO-220AB
STP45NF06	STMicroelectronics	60	38	28 @ 19A, 10V	58 @ 10V	80	Active	TO-220
STP55NF06	STMicroelectronics	60	50	18 @ 27.5A, 10V	60 @ 10V	110	Active	TO-220
STP60NF06L	STMicroelectronics	60	60	14 @ 30A, 10V	66 @ 4.5V	110	Active	TO-220

Engineering Selection Recommendations

Category 1: Direct Replacements (Vdss = 55V, Id ≥ 51A)

The following parts satisfy all primary electrical criteria and maintain TO-220 family packaging:

HUF75332P3 (onsemi): Meets minimum current requirement at 60A with 55V rating. Active product status ensures long-term availability. ROHS3 compliant. Gate charge of 85 nC @ 20V is higher than original, requiring gate driver verification for switching frequency applications.
HUF75339P3 (onsemi): Exceeds current rating at 75A with improved on-state resistance of 12 mOhm. Active status and ROHS3 compliance. Suitable for applications requiring enhanced thermal performance.
HUF75344P3 (onsemi): Highest performance option with 75A rating and 8 mOhm on-state resistance. Active status and ROHS3 compliance. Recommended for power-dense applications where thermal margin is critical.

Category 2: Voltage-Elevated Alternatives (Vdss > 55V)

IRFZ44PBF and IRFZ44RPBF (Vishay Siliconix): Both rated 60V / 50A in TO-220AB package. Active status and ROHS3 compliant. Higher voltage rating provides additional design margin. On-state resistance of 28 mOhm is higher than IRFZ44Z; suitable for lower-frequency or lower-current-density applications.
STP55NF06 (STMicroelectronics): 60V / 50A rating with 18 mOhm on-state resistance. Active status and ROHS3 compliant. Highest inventory availability (155,400 pcs). Recommended for high-volume production requiring supply security.
STP60NF06L (STMicroelectronics): 60V / 60A rating with 14 mOhm on-state resistance. Active status and ROHS3 compliant. Extended temperature range to -65°C. Suitable for applications requiring lower on-state losses.

Category 3: Obsolete Alternatives (Not Recommended for New Designs)

PHP191NQ06LT,127 (Nexperia): Obsolete status. 55V / 75A with exceptional 3.7 mOhm on-state resistance. Use only for legacy system maintenance where supply exists.
PHP79NQ08LT,127 (Nexperia): Obsolete status. 75V / 73A rating. Use only for legacy system maintenance.

Category 4: Current-Limited Alternatives (Id < 51A)

STP45NF06 (STMicroelectronics): 60V / 38A rating. Current rating below IRFZ44Z specification. Not suitable as direct replacement; use only in applications with reduced current requirements.

Frequently Asked Questions (FAQ)

Q1: Can I use HUF75332P3 as a direct replacement for IRFZ44Z?

A: HUF75332P3 meets the primary electrical criteria (55V, 60A ≥ 51A) and operates within the required temperature range. Both use TO-220 family packaging. However, gate charge increases from 43 nC to 85 nC, which may affect switching frequency performance in high-speed applications. Verify gate driver capability before substitution.

Q2: What is the difference between TO-220AB and TO-220-3 packaging?

A: Both are through-hole TO-220 family packages with identical pin configurations and thermal characteristics. TO-220AB and TO-220-3 designations refer to supplier packaging variations and are mechanically and electrically interchangeable for PCB mounting purposes.

Q3: Why do some substitutes have higher Vdss ratings (60V or 75V) than the original 55V?

A: Higher voltage ratings provide additional design margin and do not compromise functionality in 55V applications. A 60V-rated device operates safely at 55V with improved reliability. This is standard engineering practice for component selection.

Q4: Is ROHS3 compliance mandatory for my application?

A: ROHS3 compliance is required for products sold in the European Union and many other markets. If your application requires EU market access or compliance with RoHS directives, select only ROHS3-compliant alternatives. The IRFZ44Z is RoHS non-compliant; all recommended active substitutes are ROHS3 compliant.

Q5: Which substitute offers the best thermal performance?

A: HUF75344P3 provides the highest power dissipation rating (285W) and lowest on-state resistance (8 mOhm @ 75A, 10V), resulting in minimal heat generation. This part is optimal for applications requiring maximum thermal efficiency.

Q6: Can I use STP45NF06 as a substitute?

A: STP45NF06 is rated for only 38A continuous drain current, which is below the IRFZ44Z specification of 51A. This part is not suitable as a direct replacement. Use only if your application current requirement is ≤ 38A.

Q7: Why is IRFZ44Z marked as obsolete?

A: Obsolete status indicates the manufacturer has discontinued production. Existing inventory may be available from distributors, but long-term supply is not guaranteed. Active alternatives ensure design continuity and production reliability.

Q8: What is the significance of gate charge (Qg) differences?

A: Gate charge determines the energy required to switch the MOSFET on and off. Higher gate charge (e.g., 85 nC vs. 43 nC) requires more gate driver current or longer switching times. For high-frequency applications (> 100 kHz), verify that your gate driver can supply the required charge within acceptable switching time windows.

Q9: Are all substitute parts available in the same packaging?

A: Most substitutes use TO-220-3 or TO-220AB packaging, which are mechanically compatible. STP series parts use TO-220 designation. All are through-hole packages with identical pin layouts and thermal interface characteristics. Verify PCB footprint compatibility before ordering.

Q10: Which substitute has the highest inventory availability?

A: STP55NF06 (STMicroelectronics) has the highest inventory at 155,400 pieces in stock, followed by HUF75339P3 (28,300 pieces) and PHP79NQ08LT,127 (6,731 pieces). High inventory availability reduces lead time risk for production schedules.

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