FDS3512 Equivalent & Substitute Parts

Part Overview

The FDS3512 is an N-Channel 80V 4A MOSFET manufactured by onsemi in the PowerTrench® series, housed in an 8-SOIC surface mount package. This device is classified as obsolete, indicating discontinuation from active production. The FDS3512 is suitable for general-purpose switching applications requiring moderate current handling at 80V drain-source voltage ratings.

Due to its obsolete status, locating replacement units from original inventory becomes increasingly difficult. Substitute parts must maintain electrical compatibility across critical parameters including drain-source voltage, continuous drain current, on-resistance characteristics, and thermal specifications to ensure functional equivalence in existing circuit designs.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	80	V
Continuous Drain Current (Id) @ 25°C	4	A
On-Resistance (Rds On Max) @ 4A, 10V	70	mOhm
Gate Threshold Voltage (Vgs(th) Max) @ 250µA	4	V
Gate Charge (Qg Max) @ 10V	18	nC
Input Capacitance (Ciss Max) @ 40V	634	pF
Power Dissipation (Max)	2.5	W
Operating Temperature Range	-55 to 175	°C
Package Type	8-SOIC	Surface Mount
RoHS Status	ROHS3 Compliant	-

Substitute Part Grouping Explanation

Substitution eligibility for the FDS3512 is determined by the following critical parameters:

Mandatory Compatibility Criteria:

Drain-Source Voltage (Vdss): Must equal or exceed 80V
Continuous Drain Current (Id): Must equal or exceed 4A at 25°C
On-Resistance (Rds On): Must not exceed 70mOhm at rated current and gate voltage
Gate Threshold Voltage (Vgs(th)): Must not exceed 4V at 250µA
Package Type: Must be 8-SOIC or mechanically compatible surface mount variant
RoHS Compliance: Must maintain ROHS3 compliance status

Substitute Categories:

Manufacturer Recommended Substitute: FDS3590 (onsemi) — Active product with identical voltage rating, superior current rating (6.5A), lower on-resistance (39mOhm), and maintained thermal specifications within the same package family.

Parametric Equivalent: FDS3512 — Identical part number representing the original specification baseline.

Similar Alternative: 94-3660PBF (Infineon Technologies) — Higher voltage rating (100V), comparable current rating (4.5A), and similar on-resistance characteristics, suitable for applications with elevated voltage margins.

Similar Alternative: RS6N120BHTB1 (Rohm Semiconductor) — Significantly higher current rating (120A) and lower on-resistance (4.9mOhm), available in 8-HSOP package variant, applicable for high-current applications with identical voltage rating.

Parameter Comparison

Parameter	FDS3512 (Main)	FDS3590 (MFR Recommended)	94-3660PBF (Similar)	RS6N120BHTB1 (Similar)
Manufacturer	onsemi	onsemi	Infineon Technologies	Rohm Semiconductor
Product Status	Obsolete	Active	Active	Active
Vdss (V)	80	80	100	80
Id @ 25°C (A)	4	6.5	4.5	120
Rds On Max (mOhm)	70 @ 4A, 10V	39 @ 6.5A, 10V	60 @ 2.7A, 10V	4.9 @ 60A, 6V
Vgs(th) Max (V)	4 @ 250µA	4 @ 250µA	5.5 @ 250µA	4 @ 1mA
Gate Charge Qg Max (nC)	18 @ 10V	35 @ 10V	50 @ 10V	53 @ 10V
Ciss Max (pF)	634 @ 40V	1180 @ 40V	930 @ 25V	3420 @ 40V
Power Dissipation Max (W)	2.5	2.5	Not specified	104
Operating Temperature (°C)	-55 to 175	-55 to 150	Not specified	Up to 150
Package	8-SOIC	8-SOIC	8-SOIC	8-HSOP
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	Not specified

Engineering Selection Recommendations

Primary Recommendation: FDS3590

The FDS3590 is the manufacturer-recommended substitute for the obsolete FDS3512. Both devices are onsemi PowerTrench® series MOSFETs with identical 80V drain-source voltage ratings and maintained 2.5W power dissipation limits. The FDS3590 is currently in active production status, ensuring long-term availability and supply chain continuity. The FDS3590 exceeds the FDS3512 in continuous drain current (6.5A versus 4A) and provides superior on-resistance performance (39mOhm versus 70mOhm), delivering improved thermal efficiency in switching applications. Both devices maintain ROHS3 compliance and identical gate threshold voltage specifications (4V @ 250µA), ensuring direct functional compatibility in existing circuit designs. The FDS3590 operates across a slightly reduced temperature range (-55°C to 150°C versus -55°C to 175°C), which remains suitable for most industrial and commercial applications.

Secondary Alternative: 94-3660PBF

The 94-3660PBF from Infineon Technologies provides an alternative for applications requiring elevated voltage margins. This device maintains a 100V drain-source voltage rating with comparable 4.5A continuous drain current and 60mOhm on-resistance at 2.7A. The higher voltage rating accommodates circuit designs with transient overvoltage conditions. This part is in active production and ROHS3 compliant. The 94-3660PBF exhibits a higher gate threshold voltage (5.5V @ 250µA) compared to the FDS3512 (4V @ 250µA), which may require gate drive circuit adjustments in designs with marginal gate voltage supplies.

Tertiary Alternative: RS6N120BHTB1

The RS6N120BHTB1 from Rohm Semiconductor is applicable exclusively to applications requiring significantly higher current handling (120A continuous drain current). This device maintains the 80V drain-source voltage rating and delivers exceptional on-resistance performance (4.9mOhm @ 60A, 6V). The RS6N120BHTB1 is housed in an 8-HSOP package, requiring PCB layout modifications compared to the 8-SOIC footprint of the FDS3512. This substitute is suitable only for high-current switching applications where the increased current capacity and reduced on-resistance provide measurable thermal and efficiency benefits.

Frequently Asked Questions (FAQ)

Q: Can the FDS3590 directly replace the FDS3512 without circuit modifications?

A: The FDS3590 maintains electrical compatibility with the FDS3512 across all critical parameters including drain-source voltage (80V), gate threshold voltage (4V @ 250µA), and package type (8-SOIC). Direct substitution is supported without circuit modifications. The FDS3590 provides superior performance characteristics (higher current rating and lower on-resistance) that enhance rather than compromise circuit operation.

Q: What is the primary difference between the FDS3590 and FDS3512?

A: The FDS3590 is the active production successor to the obsolete FDS3512. Both devices share identical voltage ratings (80V Vdss) and power dissipation limits (2.5W). The FDS3590 provides increased continuous drain current (6.5A versus 4A) and reduced on-resistance (39mOhm versus 70mOhm), resulting in improved thermal performance and switching efficiency.

Q: Is the 94-3660PBF from Infineon a suitable replacement for the FDS3512?

A: The 94-3660PBF is a viable alternative for applications where a higher voltage rating (100V versus 80V) provides design margin benefits. The device maintains comparable current ratings (4.5A) and on-resistance characteristics (60mOhm @ 2.7A). However, the higher gate threshold voltage (5.5V @ 250µA) may require gate drive circuit evaluation in designs with limited gate voltage supplies.

Q: When should the RS6N120BHTB1 be considered as a substitute?

A: The RS6N120BHTB1 is applicable exclusively to applications requiring continuous drain currents significantly exceeding 4A. This device delivers 120A continuous current capability and exceptional on-resistance (4.9mOhm @ 60A, 6V). The 8-HSOP package requires PCB layout modifications compared to the 8-SOIC footprint. Substitution is recommended only when high-current performance requirements justify package and layout changes.

Q: Are all substitute parts RoHS compliant?

A: The FDS3590 and 94-3660PBF are confirmed ROHS3 compliant. The RS6N120BHTB1 RoHS compliance status is not specified in the provided technical data. Verification of RoHS compliance status for the RS6N120BHTB1 is required for applications subject to RoHS regulatory requirements.

Q: What is the impact of the FDS3590's higher gate charge (35nC versus 18nC) on circuit design?

A: The FDS3590's increased gate charge (35nC @ 10V versus 18nC @ 10V) requires proportionally higher gate drive current to achieve equivalent switching speed. Gate drive circuits must supply sufficient current to charge the increased capacitance within the required switching time window. This consideration is particularly relevant in high-frequency switching applications where gate drive power dissipation becomes significant.

Q: Can the FDS3512 be used in applications rated for the FDS3590?

A: The FDS3512 cannot reliably substitute for the FDS3590 in applications designed for the higher current rating (6.5A). The FDS3512's maximum continuous drain current is 4A, limiting its use to lower-current applications. Exceeding the 4A rating results in excessive junction temperature rise and potential device failure.

Q: What packaging considerations apply when substituting with the RS6N120BHTB1?

A: The RS6N120BHTB1 is housed in an 8-HSOP package, which differs from the 8-SOIC package of the FDS3512. The 8-HSOP package features enhanced thermal characteristics with a larger die pad for improved heat dissipation. PCB layout modifications are required, including updated footprint geometry and thermal via patterns. Direct socket substitution is not possible without PCB redesign.

Q: What is the operating temperature range difference between the FDS3590 and FDS3512?

A: The FDS3512 operates across -55°C to 175°C, while the FDS3590 operates across -55°C to 150°C. The FDS3590's reduced upper temperature limit (150°C versus 175°C) remains suitable for most industrial and commercial applications. Applications requiring operation above 150°C junction temperature must retain the FDS3512 or identify alternative devices with extended temperature ratings.

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