SK040R Thyristor SCR 1KV 40A TO-220 Equivalent & Substitute Parts

Part Overview

The SK040R is a Silicon Controlled Rectifier (SCR) manufactured by Littelfuse Inc., rated for 1 kV off-state voltage and 40 A RMS on-state current in a TO-220-3 through-hole package. This component is classified as discontinued at DiGi Electronics, necessitating identification of functionally equivalent alternatives for ongoing applications. The part operates across the industrial temperature range of -40°C to 125°C and complies with ROHS3 standards.

Key Parameters

Parameter	SK040R Value
Voltage - Off State	1 kV
Current - On State (It (RMS)) (Max)	40 A
Voltage - On State (Vtm) (Max)	1.8 V
Current - Gate Trigger (Igt) (Max)	40 mA
Voltage - Gate Trigger (Vgt) (Max)	1.5 V
SCR Type	Standard Recovery
Package / Case	TO-220-3
Operating Temperature	-40°C to 125°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the SK040R is determined by the following critical parameters:

Voltage Rating (Off State): Must equal or exceed 1 kV to maintain blocking capability
Current Rating (RMS): Must support minimum 40 A RMS on-state current for equivalent load handling
Package Type: Must be TO-220-3 through-hole configuration for mechanical and thermal compatibility
SCR Type: Must be Standard Recovery to match switching characteristics
Operating Temperature Range: Must encompass -40°C to 125°C
Gate Trigger Parameters: Vgt and Igt must be compatible with existing gate drive circuitry

The TYN1012TRG from STMicroelectronics is identified as a manufacturer-recommended substitute. However, this part operates at 12 A RMS maximum on-state current, which is below the 40 A RMS specification of the SK040R. This represents a current derating and is suitable only for applications where the actual load current does not exceed 12 A RMS.

Parameter Comparison

Parameter	SK040R (Littelfuse)	TYN1012TRG (STMicroelectronics)	Compatibility Notes
Voltage - Off State	1 kV	1 kV	Matched
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.3 V	TYN1012TRG requires lower gate voltage
Current - Gate Trigger (Igt) (Max)	40 mA	5 mA	TYN1012TRG requires significantly lower gate current
Voltage - On State (Vtm) (Max)	1.8 V	1.6 V	TYN1012TRG exhibits lower forward voltage drop
Current - On State (It (RMS)) (Max)	40 A	12 A	TYN1012TRG rated at 30% of SK040R current capacity
Current - Hold (Ih) (Max)	60 mA	15 mA	TYN1012TRG requires lower holding current
Current - Off State (Max)	30 µA	5 µA	TYN1012TRG exhibits lower leakage current
SCR Type	Standard Recovery	Standard Recovery	Matched
Package / Case	TO-220-3	TO-220-3	Matched
Operating Temperature	-40°C to 125°C	-40°C to 125°C	Matched
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Matched

Engineering Selection Recommendations

The TYN1012TRG is an active product from STMicroelectronics and maintains full ROHS3 compliance, making it suitable for new designs and ongoing production where component availability is required. The SK040R discontinuation status necessitates transition to an alternative.

Selection of TYN1012TRG as a substitute is valid only when the application's actual on-state current requirement does not exceed 12 A RMS. The lower gate trigger voltage (1.3 V vs. 1.5 V) and gate trigger current (5 mA vs. 40 mA) indicate improved gate sensitivity, which may require gate drive circuit adjustment to prevent unintended triggering in noise-sensitive environments.

The reduced forward voltage drop (1.6 V vs. 1.8 V) results in lower power dissipation and improved thermal performance in the TO-220 package. Applications operating at or near the 40 A RMS rating of the SK040R require evaluation of alternative 40 A class SCRs with equivalent voltage ratings and package compatibility.

Frequently Asked Questions (FAQ)

Q: Can TYN1012TRG directly replace SK040R in all applications?

A: No. The TYN1012TRG is rated for 12 A RMS maximum on-state current, compared to SK040R's 40 A RMS rating. Direct substitution is valid only for applications where actual load current does not exceed 12 A RMS. Applications requiring the full 40 A capacity require alternative 40 A class SCRs.

Q: What are the gate drive circuit implications of using TYN1012TRG?

A: The TYN1012TRG requires lower gate trigger voltage (1.3 V maximum vs. 1.5 V) and significantly lower gate trigger current (5 mA maximum vs. 40 mA). Existing gate drive circuits designed for SK040R specifications may require adjustment to prevent over-driving the gate terminal.

Q: Are both parts mechanically compatible in TO-220 mounting?

A: Yes. Both SK040R and TYN1012TRG use the TO-220-3 through-hole package configuration, providing identical mechanical and thermal interface compatibility. No PCB layout modifications are required for package substitution.

Q: What compliance certifications apply to TYN1012TRG?

A: TYN1012TRG is ROHS3 compliant and REACH unaffected, matching the regulatory status of SK040R. Both parts are classified under ECCN EAR99 and HTSUS 8541.30.0080.

Q: How do the thermal characteristics compare?

A: The TYN1012TRG exhibits lower forward voltage drop (1.6 V vs. 1.8 V) and lower on-state current rating, resulting in reduced power dissipation. For equivalent current levels, TYN1012TRG generates less heat in the TO-220 package, improving thermal margin.

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