S4040R SCR 400V 40A TO-220 Equivalent & Substitute Parts

Part Overview

The S4040R is a Standard Recovery SCR (Silicon Controlled Rectifier) rated for 400V off-state voltage and 40A RMS on-state current, manufactured by Littelfuse Inc. in a TO-220-3 through-hole package. This component is discontinued at DiGi Electronics, making equivalent substitutes necessary for ongoing design support and procurement. The S4040R serves applications requiring thyristor switching and power control in industrial and consumer electronics operating within its specified voltage and current ratings.

Key Parameters

Parameter	Value	Unit
Voltage - Off State	400	V
Current - On State (It (RMS))	40	A
Voltage - On State (Vtm) (Max)	1.8	V
Current - Gate Trigger (Igt) (Max)	40	mA
SCR Type	Standard Recovery	-
Package / Case	TO-220-3	-
Operating Temperature	-40 to 125	°C
RoHS Status	ROHS3 Compliant	-

Substitute Part Grouping Explanation

Substitution eligibility for the S4040R is determined by the following critical parameters:

Primary Matching Criteria:

Off-state voltage rating equal to or greater than 400V
RMS on-state current rating equal to or greater than 40A
Standard Recovery SCR type
TO-220-3 package configuration
Through-hole mounting compatibility
Operating temperature range encompassing -40°C to 125°C

Secondary Compatibility Factors:

Gate trigger voltage and current within acceptable application ranges
On-state voltage drop compatible with circuit design
Non-repetitive surge current capability
RoHS3 compliance and environmental certifications

Two substitute parts meet these criteria with distinct voltage and current characteristics suitable for different application scenarios.

Parameter Comparison

Parameter	S4040R (Littelfuse)	TYN408GRG (STMicroelectronics)	TYN640RG (STMicroelectronics)
Voltage - Off State	400 V	400 V	600 V
Current - On State (It (RMS))	40 A	8 A	40 A
Voltage - On State (Vtm) (Max)	1.8 V	1.6 V	1.6 V
Current - Gate Trigger (Igt) (Max)	40 mA	25 mA	35 mA
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.5 V	1.3 V
Current - Hold (Ih) (Max)	60 mA	45 mA	75 mA
Current - Off State (Max)	10 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 to 125 °C	-40 to 125 °C	-40 to 125 °C
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Discontinued	Active	Active

Engineering Selection Recommendations

TYN640RG (Primary Substitute): The TYN640RG from STMicroelectronics provides direct current and power handling equivalence to the S4040R with identical 40A RMS on-state current rating. This part maintains the same TO-220-3 package, operating temperature range, and RoHS3 compliance. The TYN640RG offers higher off-state voltage (600V versus 400V), making it suitable for applications where the S4040R was used in 400V circuits, as higher voltage ratings are backward-compatible in lower-voltage applications. The part is currently in active production status with 2200 units in stock, ensuring long-term availability.

TYN408GRG (Limited Scope Substitute): The TYN408GRG from STMicroelectronics matches the 400V off-state voltage rating of the S4040R but is rated for only 8A RMS on-state current. This part is suitable only for applications where the original design operated at significantly reduced current levels below the S4040R's 40A capability. The TYN408GRG maintains identical package, temperature range, and RoHS3 compliance. This substitute is appropriate for current-limited circuits or where thermal management constraints restrict actual operating current to 8A or below.

Both substitutes are manufactured by STMicroelectronics, carry ROHS3 compliance, and are in active production status, providing superior long-term availability compared to the discontinued S4040R.

Frequently Asked Questions (FAQ)

Q: Can the TYN640RG replace the S4040R in all applications? A: The TYN640RG is electrically compatible with the S4040R for applications operating at 400V or below. The higher 600V rating does not create incompatibility in lower-voltage circuits. Both parts share identical RMS current capacity (40A), package configuration (TO-220-3), and operating temperature range (-40°C to 125°C). Verification of gate drive circuit compatibility is recommended due to minor differences in gate trigger specifications.

Q: When should the TYN408GRG be selected? A: The TYN408GRG is appropriate only when the application's actual operating current is 8A RMS or below. This part matches the S4040R's 400V off-state voltage and package type but cannot handle the full 40A current capacity. Selection of this part requires confirmation that circuit design or thermal constraints limit current to within its 8A rating.

Q: Are there package compatibility concerns with these substitutes? A: All three parts use the TO-220-3 through-hole package configuration. Physical mounting and thermal interface compatibility are identical. PCB layout and heatsink attachment remain unchanged between the S4040R and both substitute parts.

Q: What are the compliance and availability advantages of these substitutes? A: Both TYN640RG and TYN408GRG are in active production status with current inventory availability (2200 and 1565 units respectively), compared to the S4040R's discontinued status. Both substitutes maintain ROHS3 compliance and carry REACH Unaffected status, ensuring regulatory compliance for new designs and ongoing production.

Q: How do gate trigger specifications differ between these parts? A: The S4040R specifies 40mA maximum gate trigger current; the TYN640RG requires 35mA and the TYN408GRG requires 25mA. All three parts share 1.5V maximum gate trigger voltage (TYN640RG is 1.3V). Gate drive circuits designed for the S4040R will operate the substitutes within specification, though the lower trigger current requirements of the substitutes may provide improved gate drive efficiency.

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