S4055R Equivalent & Substitute Parts

Part Overview

The S4055R is a Silicon Controlled Rectifier (SCR) manufactured by Littelfuse Inc., rated for 400V off-state voltage with 55A RMS current capacity in a TO-220-3 through-hole package. This component is discontinued at DiGi Electronics, making equivalent substitutes necessary for ongoing production and maintenance applications. The S4055R serves as a high-current thyristor for power control and switching applications requiring standard recovery characteristics and robust thermal performance across industrial temperature ranges.

Key Parameters

Parameter	S4055R Value
Voltage - Off State	400 V
Current - On State (It (RMS)) (Max)	55 A
Voltage - On State (Vtm) (Max)	1.8 V
Voltage - Gate Trigger (Vgt) (Max)	1.5 V
Current - Gate Trigger (Igt) (Max)	40 mA
Current - Hold (Ih) (Max)	60 mA
SCR Type	Standard Recovery
Operating Temperature	-40°C ~ 125°C
Package / Case	TO-220-3
Mounting Type	Through Hole

Substitute Part Grouping Explanation

Substitution of the S4055R requires matching the following critical electrical and mechanical parameters:

Voltage Rating (Off State): 400V minimum to maintain blocking capability
Current Capacity (RMS): Minimum 55A to handle specified load conditions
Gate Trigger Characteristics: Vgt ≤ 1.5V and Igt ≤ 40mA for compatible gate drive circuits
On-State Voltage: ≤ 1.8V to ensure thermal performance alignment
Package Type: TO-220-3 through-hole configuration for PCB compatibility
SCR Type: Standard Recovery for switching speed consistency
Temperature Range: -40°C to 125°C operational envelope

The TYN408GRG does not meet the current capacity requirement (8A RMS vs. 55A RMS required), making it unsuitable as a direct substitute for the S4055R in applications requiring the full 55A rating.

Parameter Comparison

Parameter	S4055R (Littelfuse)	TYN408GRG (STMicroelectronics)	Match Status
Voltage - Off State	400 V	400 V	Match
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.5 V	Match
Current - Gate Trigger (Igt) (Max)	40 mA	25 mA	Compatible
Voltage - On State (Vtm) (Max)	1.8 V	1.6 V	Compatible
Current - On State (It (RMS)) (Max)	55 A	8 A	Mismatch
Current - Hold (Ih) (Max)	60 mA	45 mA	Compatible
SCR Type	Standard Recovery	Standard Recovery	Match
Operating Temperature	-40°C ~ 125°C	-40°C ~ 125°C	Match
Package / Case	TO-220-3	TO-220-3	Match
Mounting Type	Through Hole	Through Hole	Match

Engineering Selection Recommendations

The TYN408GRG shares identical voltage ratings, gate trigger voltage, SCR type classification, and package configuration with the S4055R. Both components are ROHS3 compliant with MSL-1 moisture sensitivity ratings and operate across the same temperature envelope.

However, the TYN408GRG is rated for 8A RMS maximum current, which represents a 6.875:1 reduction from the S4055R's 55A RMS specification. This current capacity differential disqualifies the TYN408GRG as a functional equivalent for applications requiring the full 55A current handling capability of the S4055R.

The TYN408GRG is suitable only for applications where the required RMS current does not exceed 8A and where the lower surge current rating (80A/84A vs. 550A/650A) is acceptable. For S4055R replacement in high-current applications, alternative 400V SCR devices with 55A or greater RMS current ratings must be evaluated.

Frequently Asked Questions (FAQ)

Q: Can the TYN408GRG replace the S4055R in my application?

A: Only if your application requires maximum 8A RMS current. The TYN408GRG cannot handle the 55A RMS current specification of the S4055R. Exceeding the TYN408GRG's current rating will cause thermal failure and component destruction.

Q: What makes these parts similar despite the current rating difference?

A: Both devices share identical 400V off-state voltage ratings, matching gate trigger voltage specifications (1.5V), standard recovery SCR classification, TO-220-3 package configuration, and -40°C to 125°C operating temperature range. These similarities apply only to voltage and switching characteristics, not current capacity.

Q: Are there package compatibility concerns between S4055R and TYN408GRG?

A: Both components use TO-220-3 through-hole packages with identical pinout and mounting requirements. PCB footprint and thermal interface compatibility are equivalent. Package compatibility is not a limiting factor for substitution evaluation.

Q: What is the significance of the current rating mismatch?

A: The current rating defines the maximum continuous RMS current the device can conduct without exceeding thermal limits. The S4055R is designed for 55A applications; the TYN408GRG is designed for 8A applications. Using an undersized device in a high-current circuit violates the component's electrical specifications and creates fire and safety hazards.

Q: Are both parts RoHS compliant?

A: Yes. Both the S4055R and TYN408GRG are ROHS3 compliant with MSL-1 moisture sensitivity ratings, meeting current environmental and reliability standards.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message