FDMS8670S N-Channel 30V 20A/42A MOSFET Equivalent & Substitute Parts

Part Overview

The FDMS8670S is an N-Channel MOSFET manufactured by onsemi, rated for 30V drain-to-source voltage with continuous drain current of 20A at Ta (ambient temperature) and 42A at Tc (case temperature). This device is housed in an 8-PQFN (5x6) surface mount package and belongs to the PowerTrench® and SyncFET™ series. The part is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	Value	Unit
Drain-to-Source Voltage (Vdss)	30	V
Continuous Drain Current @ 25°C (Ta)	20	A
Continuous Drain Current @ 25°C (Tc)	42	A
On-Resistance (Rds On) @ 20A, 10V	3.5	mOhm
Gate Threshold Voltage (Vgs(th)) @ 1mA	3	V
Gate Charge (Qg) @ 10V	73	nC
Input Capacitance (Ciss) @ 15V	4000	pF
Power Dissipation (Ta)	2.5	W
Power Dissipation (Tc)	78	W
Operating Temperature Range	-55 to 150	°C
Package Type	8-PQFN (5x6)	—
FET Type	N-Channel	—
Technology	MOSFET (Metal Oxide)	—

Substitute Part Grouping Explanation

Substitution of the FDMS8670S is determined by strict alignment of the following electrical and mechanical parameters:

Primary Substitution Criteria:

Drain-to-Source Voltage (Vdss): Must equal or exceed 30V
Continuous Drain Current (Id @ Ta): Must meet or exceed 20A at ambient temperature
On-Resistance (Rds On): Lower or equivalent values ensure compatible performance
Gate Threshold Voltage (Vgs(th)): Must be compatible with existing gate drive circuits
Package Type: Surface mount 8-pin configurations (8-PQFN, 8-VSONP, PG-TDSON-8-5) with 5x6mm footprints are mechanically compatible
Operating Temperature Range: Must support -55°C to 150°C minimum
Compliance: RoHS3 compliant, REACH unaffected, MSL 1 (Unlimited)

Substitute parts are grouped into two categories based on current rating and on-resistance characteristics:

Category A (Higher Current Capability): Parts with continuous drain current ≥28A at Ta, suitable for direct replacement with enhanced thermal performance.

Category B (Moderate Current Capability): Parts with continuous drain current between 17A and 24A at Ta, suitable for applications where the full 20A rating is not continuously required.

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ Ta (A)	Id @ Tc (A)	Rds On (mOhm)	Vgs(th) (V)	Qg (nC)	Ciss (pF)	Package	Status
FDMS8670S	onsemi	30	20	42	3.5	3	73	4000	8-PQFN (5x6)	Obsolete
NTMFS4C05NT1G	onsemi	30	11.9	—	3.4	2.2	14	1972	5-DFN (5x6)	Active
BSC042N03MSGATMA1	Infineon	30	17	93	4.2	2	55	4300	PG-TDSON-8-5	Active
BSC050N03LSGATMA1	Infineon	30	18	80	5	2.2	35	2800	PG-TDSON-8-5	Active
BSC057N03LSGATMA1	Infineon	30	17	71	5.7	2.2	30	2400	PG-TDSON-8-5	Obsolete
CSD16413Q5A	Texas Instruments	25	24	100	3.9	1.9	11.7	1780	8-VSONP (5x6)	Active
CSD17301Q5A	Texas Instruments	30	28	100	2.6	1.55	25	3480	8-VSONP (5x6)	Active
CSD17305Q5A	Texas Instruments	30	29	100	3.4	1.6	18.3	2600	8-VSONP (5x6)	Active
CSD17306Q5A	Texas Instruments	30	24	100	3.7	1.6	15.3	2170	8-VSONP (5x6)	Active
CSD17501Q5A	Texas Instruments	30	—	100	2.9	1.8	17	2630	8-VSONP (5x6)	Active
CSD17581Q5A	Texas Instruments	30	24	123	3.4	1.7	54	3640	8-VSONP (5x6)	Active

Engineering Selection Recommendations

Primary Substitutes (Recommended for Direct Replacement):

CSD17305Q5A (Texas Instruments, NexFET™ series) is the preferred substitute. It meets all critical electrical parameters: 30V Vdss, 29A continuous drain current at Ta (exceeding the 20A requirement), and 3.4mOhm on-resistance. The device is active, RoHS3 compliant, and housed in an 8-VSONP (5x6) package with identical footprint compatibility. Gate threshold voltage of 1.6V is lower than the FDMS8670S, requiring verification of gate drive circuit compatibility.

CSD17306Q5A (Texas Instruments, NexFET™ series) provides equivalent performance with 24A continuous drain current at Ta and 3.7mOhm on-resistance. This part is active and RoHS3 compliant with the same package footprint.

CSD17301Q5A (Texas Instruments, NexFET™ series) offers superior performance with 28A continuous drain current at Ta and 2.6mOhm on-resistance, providing enhanced thermal efficiency. This part is active and RoHS3 compliant.

Secondary Substitutes (Conditional Replacement):

BSC042N03MSGATMA1 (Infineon, OptiMOS™ series) provides 17A continuous drain current at Ta with 4.2mOhm on-resistance. This part is active and RoHS3 compliant but falls below the 20A continuous current specification. Suitable only for applications where peak current requirements do not exceed 17A sustained operation.

BSC050N03LSGATMA1 (Infineon, OptiMOS™ series) provides 18A continuous drain current at Ta with 5mOhm on-resistance. This part is active and RoHS3 compliant but also falls below the 20A specification. Suitable for reduced-current applications.

CSD17581Q5A (Texas Instruments, NexFET™ series) provides 24A continuous drain current at Ta with 3.4mOhm on-resistance and 83W power dissipation at Tc, exceeding the FDMS8670S thermal capability. This part is active and RoHS3 compliant.

Not Recommended:

NTMFS4C05NT1G (onsemi) provides only 11.9A continuous drain current, falling significantly below the 20A requirement. Package is 5-DFN, which differs from the 8-pin configurations of other substitutes.

CSD16413Q5A (Texas Instruments) has a Vdss rating of 25V, below the required 30V specification, and is therefore not suitable.

BSC057N03LSGATMA1 (Infineon) is listed as obsolete and provides only 17A continuous drain current at Ta, making it unsuitable for replacement purposes.

All recommended substitutes maintain RoHS3 compliance, REACH unaffected status, and MSL 1 (Unlimited) moisture sensitivity level, ensuring regulatory and environmental compatibility with the original FDMS8670S.

Frequently Asked Questions (FAQ)

Q: Can CSD17305Q5A directly replace FDMS8670S in existing PCB layouts?

A: The CSD17305Q5A uses an 8-VSONP (5x6) package, which shares the same 5x6mm footprint as the FDMS8670S 8-PQFN package. Pin configuration and lead spacing are compatible for direct PCB substitution. However, gate threshold voltage differs (1.6V vs. 3V), requiring verification that existing gate drive circuits can operate at the lower threshold.

Q: What is the primary difference between the Texas Instruments NexFET™ and Infineon OptiMOS™ substitutes?

A: Texas Instruments NexFET™ parts (CSD17305Q5A, CSD17306Q5A, CSD17301Q5A, CSD17581Q5A) feature lower gate threshold voltages (1.55V to 1.8V) and lower on-resistance values, providing superior switching performance and thermal efficiency. Infineon OptiMOS™ parts (BSC042N03MSGATMA1, BSC050N03LSGATMA1) feature higher gate threshold voltages (2V to 2.2V) and higher on-resistance values, requiring higher gate drive voltage but offering more robust gate drive margin.

Q: Why is NTMFS4C05NT1G not recommended as a substitute?

A: The NTMFS4C05NT1G provides only 11.9A continuous drain current at ambient temperature, which is 40% below the FDMS8670S 20A specification. Additionally, it uses a 5-DFN package with only 5 leads, whereas the FDMS8670S uses an 8-pin package. This part is suitable only for applications requiring significantly lower current ratings.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All recommended substitute parts are RoHS3 compliant, REACH unaffected, and carry MSL 1 (Unlimited) moisture sensitivity level ratings, matching the environmental and regulatory compliance of the original FDMS8670S.

Q: What is the significance of the Tc (case temperature) current rating versus Ta (ambient temperature) rating?

A: The Ta rating represents continuous drain current under ambient temperature conditions (typically 25°C) without active cooling. The Tc rating represents continuous drain current when the device case is actively cooled to 25°C. For applications with thermal management (heatsinks, forced air cooling), the Tc rating applies. The FDMS8670S provides 20A at Ta and 42A at Tc. Substitute parts with higher Tc ratings (80A to 123A) indicate superior thermal performance under active cooling conditions.

Q: Can BSC042N03MSGATMA1 or BSC050N03LSGATMA1 be used if the application does not require the full 20A continuous current?

A: Yes, if the application's sustained current requirement is below 17A to 18A respectively, these Infineon parts are suitable substitutes. However, design margins should account for the higher on-resistance values (4.2mOhm to 5mOhm) compared to the FDMS8670S (3.5mOhm), resulting in increased power dissipation and heat generation.

Q: What gate drive voltage is required for each substitute part?

A: The FDMS8670S operates with gate drive voltages of 4.5V (minimum) to 10V (maximum). Texas Instruments NexFET™ substitutes operate with lower gate drive voltages (3V to 8V for CSD17301Q5A, 3V to 8V for CSD17305Q5A, 3V to 8V for CSD17306Q5A, 4.5V to 10V for CSD17501Q5A and CSD17581Q5A). Infineon OptiMOS™ substitutes operate with 4.5V to 10V gate drive voltages, matching the original specification. Verify that existing gate drive circuits can supply the required voltage range for the selected substitute.

Q: Is the onsemi NTMFS4C05NT1G from the same manufacturer as the FDMS8670S?

A: Yes, both are manufactured by onsemi. However, the NTMFS4C05NT1G is not a suitable substitute due to its significantly lower current rating (11.9A vs. 20A) and different package configuration (5-DFN vs. 8-PQFN).

Q: Which substitute offers the best thermal performance?

A: CSD17581Q5A provides the highest power dissipation capability at case temperature (83W at Tc), followed by CSD17301Q5A (100A at Tc with lower on-resistance). Both exceed the FDMS8670S thermal rating of 78W at Tc. For applications requiring maximum thermal headroom, CSD17581Q5A is recommended.

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