S8055R Equivalent & Substitute Parts

Part Overview

The S8055R is a silicon-controlled rectifier (SCR) manufactured by Littelfuse Inc., rated for 800 V off-state voltage and 55 A RMS on-state current in a TO-220-3 through-hole package. This component is classified as discontinued at DiGi Electronics, making equivalent substitute parts necessary for ongoing design requirements and procurement planning. The S8055R operates across a temperature range of -40°C to 125°C and complies with ROHS3 standards.

Key Parameters

Parameter	S8055R (Littelfuse)
Voltage - Off State	800 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
Current - Off State (Max)	20 µA
SCR Type	Standard Recovery
Package / Case	TO-220-3
Operating Temperature	-40°C ~ 125°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the S8055R is determined by the following critical electrical and mechanical parameters:

Off-state voltage rating: Must equal 800 V
Package type: Must be TO-220-3 through-hole configuration
SCR type: Must be Standard Recovery
Operating temperature range: Must support -40°C to 125°C
RoHS compliance: Must meet ROHS3 standards

The substitute parts TYN825RG and TYN840RG, both manufactured by STMicroelectronics, meet these core requirements. However, they differ in on-state current ratings: TYN825RG is rated for 25 A RMS, and TYN840RG is rated for 40 A RMS, compared to the S8055R's 55 A RMS rating. These differences establish distinct application boundaries based on circuit current requirements.

Parameter Comparison

Parameter	S8055R (Littelfuse)	TYN825RG (STMicroelectronics)	TYN840RG (STMicroelectronics)
Voltage - Off State	800 V	800 V	800 V
Current - On State (It (RMS)) (Max)	55 A	25 A	40 A
Voltage - On State (Vtm) (Max)	1.8 V	1.6 V	1.6 V
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.3 V	1.3 V
Current - Gate Trigger (Igt) (Max)	40 mA	40 mA	35 mA
Current - Hold (Ih) (Max)	60 mA	50 mA	75 mA
Current - Off State (Max)	20 µA	5 µA	5 µA
SCR Type	Standard Recovery	Standard Recovery	Standard Recovery
Package / Case	TO-220-3	TO-220-3	TO-220-3
Operating Temperature	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Discontinued at DiGi Electronics	Active	Active

Engineering Selection Recommendations

TYN840RG is the preferred substitute for applications requiring maximum current capacity closest to the S8055R specification. With a 40 A RMS rating, it accommodates circuits designed for up to 40 A continuous operation. This part is currently active in production and maintains full ROHS3 compliance and REACH unaffected status.

TYN825RG is suitable for applications with lower current requirements, rated for 25 A RMS. This part is also active in production with equivalent compliance certifications and offers the highest inventory availability (17,700 units).

Both substitute parts feature improved gate trigger voltage characteristics (1.3 V maximum versus 1.5 V) and reduced off-state leakage current (5 µA versus 20 µA), representing performance enhancements over the discontinued S8055R.

Frequently Asked Questions (FAQ)

Q: Can TYN825RG or TYN840RG be used in circuits originally designed for S8055R?

A: Substitution depends on circuit current requirements. TYN840RG supports up to 40 A RMS and is suitable for designs operating at or below this threshold. TYN825RG is limited to 25 A RMS. If the original design requires the full 55 A RMS capability of the S8055R, neither substitute is appropriate without circuit redesign.

Q: Are the package dimensions identical between S8055R and the substitute parts?

A: All three parts use the TO-220-3 through-hole package configuration. Physical mounting and thermal interface characteristics are compatible.

Q: What is the impact of lower gate trigger voltage on circuit operation?

A: The substitute parts feature a maximum gate trigger voltage of 1.3 V compared to the S8055R's 1.5 V. This represents improved gate sensitivity and does not negatively affect circuit compatibility. Gate drive circuits designed for the S8055R will function with the substitute parts.

Q: Are there compliance or certification differences between these parts?

A: All three parts are ROHS3 compliant. TYN825RG and TYN840RG carry additional REACH unaffected status certification. No compliance barriers exist for substitution.

Q: What is the significance of reduced off-state leakage current in the substitute parts?

A: The substitute parts exhibit 5 µA maximum off-state leakage compared to the S8055R's 20 µA. This represents lower standby power dissipation and improved blocking characteristics, which are beneficial for circuit performance.

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