FDC655AN N-Channel 30V 6.3A MOSFET Equivalent & Substitute Parts

Part Overview

The FDC655AN is an N-Channel 30V 6.3A MOSFET manufactured by onsemi in the PowerTrench® series, housed in a SuperSOT™-6 (SOT-23-6 Thin) surface mount package. This device is classified as obsolete, necessitating identification of active equivalent and substitute parts for new designs and ongoing production requirements. The FDC655AN serves as a general-purpose switching transistor for applications requiring moderate current handling at 30V drain-source voltage ratings.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	30	V
Continuous Drain Current (Id) @ 25°C	6.3	A
On-State Resistance (Rds On) @ 6.3A, 10V	27	mOhm
Gate Threshold Voltage (Vgs(th)) @ 250µA	3	V
Gate Charge (Qg) @ 5V	13	nC
Input Capacitance (Ciss) @ 15V	830	pF
Power Dissipation (Max)	1.6	W
Operating Temperature Range	-55 to 150	°C
Package Type	SOT-23-6 Thin / TSOT-23-6	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitution of the FDC655AN is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Drain-Source Voltage (Vdss): Must equal or exceed 30V
Continuous Drain Current (Id): Must equal or exceed 6.3A at 25°C
On-State Resistance (Rds On): Lower or equivalent values ensure compatible switching performance
Gate Threshold Voltage (Vgs(th)): Must be compatible with drive circuit voltage levels
Package Type: Surface mount SOT-23-6 or TSOT-23-6 variants for mechanical compatibility
Operating Temperature Range: Must support -55°C to 150°C junction temperature

Substitution Categories:

Category 1: Direct Equivalents (Same Electrical Performance) Parts meeting or exceeding all primary electrical specifications with identical or superior performance characteristics and active product status.

Category 2: Functional Alternatives (Reduced Current Rating) Parts with lower continuous drain current ratings (2A to 4.5A) suitable for applications not requiring the full 6.3A capability. These parts maintain 30V Vdss rating and compatible package types.

Category 3: Enhanced Performance Variants Parts from the same manufacturer (onsemi) with improved electrical characteristics and active product status.

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ 25°C (A)	Rds On @ 10V (mOhm)	Vgs(th) @ 250µA (V)	Qg @ Vgs (nC)	Ciss @ 15V (pF)	Power Diss. (W)	Package	Status
FDC655AN	onsemi	30	6.3	27	3	13 @ 5V	830	1.6	SOT-23-6	Obsolete
FDC655BN	onsemi	30	6.3	25	3	15 @ 10V	570	1.6	SOT-23-6	Active
DMG6402LVT-7	Diodes Inc.	30	6	30 @ 7A	2	11.4 @ 10V	498	1.75	TSOT-23-6	Active
RTQ045N03TR	Rohm	30	4.5	43 @ 4.5A	1.5	10.7 @ 4.5V	540	1.25	TSMT6	Not For New Designs
RTQ035N03TR	Rohm	30	3.5	54 @ 3.5A	1.5	6.4 @ 4.5V	285	1.25	TSMT6	Not For New Designs
RSQ045N03TR	Rohm	30	4.5	38 @ 4.5A	2.5	9.5 @ 5V	520	0.6	TSMT6	Active
RSQ020N03TR	Rohm	30	2	134 @ 2A	2.5	3.1 @ 5V	110	0.6	TSMT6	Active
RTQ020N03TR	Rohm	30	2	125 @ 2A	1.5	3.3 @ 4.5V	135	1.25	TSMT6	Active

Engineering Selection Recommendations

Primary Recommendation: FDC655BN

The FDC655BN is the direct active equivalent of the FDC655AN. Both parts share identical electrical specifications (30V Vdss, 6.3A Id), the same PowerTrench® series designation, and compatible SOT-23-6 packaging. The FDC655BN features improved on-state resistance (25mOhm versus 27mOhm) and reduced input capacitance (570pF versus 830pF), providing superior switching performance. The FDC655BN carries active product status with RoHS3 compliance and unlimited moisture sensitivity level (MSL 1), making it suitable for new designs and production applications.

Secondary Recommendation: DMG6402LVT-7

The DMG6402LVT-7 manufactured by Diodes Incorporated provides near-equivalent performance with 30V Vdss and 6A continuous drain current. This part maintains compatibility with the 30V voltage class and delivers comparable current handling. The DMG6402LVT-7 is active, RoHS3 compliant, and housed in TSOT-23-6 packaging. The slightly higher power dissipation (1.75W versus 1.6W) and marginally higher on-state resistance (30mOhm at 7A) represent acceptable trade-offs for applications where Diodes Incorporated sourcing is preferred.

Alternative Recommendations for Reduced Current Applications:

For applications requiring less than 6.3A continuous drain current, the following active parts provide suitable alternatives:

RSQ045N03TR (Rohm): 30V, 4.5A, active status, 0.6W power dissipation, TSMT6 package
RTQ020N03TR (Rohm): 30V, 2A, active status, 1.25W power dissipation, TSMT6 package

These parts maintain 30V Vdss compatibility and offer active product status. Selection depends on specific current requirements and thermal design constraints.

Parts Not Recommended for New Designs:

RTQ045N03TR and RTQ035N03TR carry "Not For New Designs" product status and should be avoided in new development projects, despite active inventory availability.

Frequently Asked Questions (FAQ)

Q: Can FDC655BN directly replace FDC655AN in existing designs?

A: Yes. The FDC655BN is the active equivalent of the FDC655AN with identical electrical ratings (30V Vdss, 6.3A Id) and compatible SOT-23-6 packaging. The FDC655BN features improved electrical characteristics (lower Rds On and Ciss) and carries active product status, making it the preferred direct replacement.

Q: What is the difference between SOT-23-6 and TSMT6 packages?

A: SOT-23-6 (SuperSOT™-6 or TSOT-23-6) and TSMT6 (SC-95) are distinct surface mount package types with different physical dimensions and pin configurations. While both are six-pin surface mount packages, they are not mechanically interchangeable. PCB layout and footprint design must match the specific package type. Verify package compatibility before substitution.

Q: Why is the FDC655AN marked as obsolete?

A: The FDC655AN is obsolete due to product lifecycle management by onsemi. The FDC655BN serves as the active replacement, offering equivalent or superior electrical performance with current manufacturing support and compliance certifications.

Q: Can I use DMG6402LVT-7 if my application requires exactly 6.3A?

A: The DMG6402LVT-7 is rated for 6A continuous drain current, which is 0.3A below the FDC655AN specification. For applications with strict 6.3A requirements, the FDC655BN is the appropriate choice. For applications with 6A or lower current demands, the DMG6402LVT-7 is suitable.

Q: What does "Not For New Designs" status mean?

A: Parts marked "Not For New Designs" (such as RTQ045N03TR and RTQ035N03TR) are in mature or declining production phases. While inventory may be available, manufacturers do not recommend these parts for new product development. Use active-status parts (FDC655BN, DMG6402LVT-7, RSQ045N03TR) for new designs.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended substitute parts (FDC655BN, DMG6402LVT-7, RSQ045N03TR, RSQ020N03TR, RTQ020N03TR) carry RoHS3 compliance certification. The original FDC655AN does not list RoHS status, which is another reason to transition to active equivalents.

Q: How do gate charge (Qg) differences affect circuit design?

A: Gate charge determines the energy required to switch the MOSFET on and off. Lower gate charge (such as DMG6402LVT-7 at 11.4nC) reduces driver power consumption and enables faster switching compared to higher gate charge devices (FDC655AN at 13nC). For most applications, these differences are negligible; however, high-frequency switching circuits may benefit from lower Qg devices.

Q: What is the significance of input capacitance (Ciss) in substitution?

A: Input capacitance affects gate drive requirements and switching speed. The FDC655BN (570pF) has lower Ciss than the FDC655AN (830pF), resulting in faster switching transitions and reduced driver stress. Lower Ciss is generally advantageous; however, existing gate drive circuits designed for the FDC655AN will function with the FDC655BN without modification.

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