S4040RQ2TP Equivalent & Substitute Parts

Part Overview

The S4040RQ2TP is a Silicon Controlled Rectifier (SCR) manufactured by Littelfuse Inc., rated for 400V off-state voltage with 40A RMS on-state current capability. This thyristor is designed for standard recovery applications in Through Hole TO-220 packaging and maintains Active product status with full RoHS3 compliance. Substitute parts are identified when electrical parameters remain within acceptable operating ranges while maintaining mechanical compatibility and thermal characteristics.

Key Parameters

Parameter	Value	Unit
Voltage - Off State	400	V
Current - On State (It (RMS))	40	A
Voltage - Gate Trigger (Vgt) (Max)	1.5	V
Current - Gate Trigger (Igt) (Max)	40	mA
Voltage - On State (Vtm) (Max)	1.8	V
SCR Type	Standard Recovery	-
Mounting Type	Through Hole	-
Package / Case	TO-220-3	-
Operating Temperature	-40 to 125	°C

Substitute Part Grouping Explanation

The S4055RTP qualifies as a parametric equivalent based on the following criteria:

Matching Parameters:

Off-state voltage: 400V (identical)
Gate trigger voltage (Vgt): 1.5V maximum (identical)
Gate trigger current (Igt): 40mA maximum (identical)
On-state voltage (Vtm): 1.8V maximum (identical)
SCR type: Standard Recovery (identical)
Mounting type: Through Hole (identical)
Package class: TO-220-3 (identical)
Operating temperature range: -40°C to 125°C (identical)
RoHS3 compliance: Yes (identical)

Distinguishing Parameter:

Current - On State (It (RMS)): S4040RQ2TP rated 40A; S4055RTP rated 55A

The S4055RTP provides higher RMS current capacity while maintaining all critical gate control and voltage parameters. This substitution is valid for applications where the 40A rating is not a limiting design constraint.

Parameter Comparison

Parameter	S4040RQ2TP	S4055RTP	Unit
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	-
Category	Thyristors	Thyristors	-
Voltage - Off State	400	400	V
Voltage - Gate Trigger (Vgt) (Max)	1.5	1.5	V
Current - Gate Trigger (Igt) (Max)	40	40	mA
Voltage - On State (Vtm) (Max)	1.8	1.8	V
Current - On State (It (AV)) (Max)	25	35	A
Current - On State (It (RMS)) (Max)	40	55	A
Current - Hold (Ih) (Max)	60	60	mA
Current - Off State (Max)	10	10	µA
SCR Type	Standard Recovery	Standard Recovery	-
Operating Temperature	-40 to 125	-40 to 125	°C
Mounting Type	Through Hole	Through Hole	-
Package / Case	TO-220-3	TO-220-3	-
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	-
Product Status	Active	Active	-

Engineering Selection Recommendations

Both the S4040RQ2TP and S4055RTP maintain Active product status with full RoHS3 compliance and REACH unaffected designation. Selection between these parts depends on application current requirements:

S4040RQ2TP is appropriate for designs with maximum RMS current demand of 40A or less, where the lower current rating aligns with circuit specifications.

S4055RTP is suitable for applications requiring up to 55A RMS current capacity. The higher current rating provides design margin without compromising gate control characteristics or thermal operating range. Both parts share identical gate trigger parameters, on-state voltage characteristics, and package footprint, ensuring functional compatibility in TO-220 mounting applications.

Frequently Asked Questions (FAQ)

Q: Can S4055RTP replace S4040RQ2TP in existing designs?

A: Yes, provided the application does not require the lower current rating as a design constraint. The S4055RTP maintains identical gate trigger voltage, gate trigger current, on-state voltage, and operating temperature specifications. The higher RMS current rating (55A vs 40A) represents increased capacity, not a functional change.

Q: Are the package dimensions identical?

A: Both parts use TO-220-3 package classification. The S4040RQ2TP specifies TO-220 Non-Isolated Tab, while the S4055RTP specifies TO-220AB-R. Verify mechanical compatibility with your PCB layout and thermal management design before substitution.

Q: Do gate control parameters differ between these parts?

A: No. Both parts share identical maximum gate trigger voltage (1.5V) and maximum gate trigger current (40mA), ensuring equivalent gate drive circuit requirements and control characteristics.

Q: What is the temperature operating range for both parts?

A: Both the S4040RQ2TP and S4055RTP operate across -40°C to 125°C, providing identical thermal specifications for system design.

Q: Are compliance certifications the same?

A: Yes. Both parts are RoHS3 compliant, REACH unaffected, and classified under ECCN EAR99 with identical HTSUS coding (8541.30.0080).

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