S4X8ES2 Equivalent & Substitute Parts

Part Overview

The S4X8ES2 is a 400 V, 800 mA sensitive gate silicon controlled rectifier (SCR) manufactured by Littelfuse Inc. in a through-hole TO-92 package. This component is classified as Active and suitable for general-purpose thyristor applications requiring controlled rectification at moderate voltage and current levels.

Equivalent and substitute parts are necessary when the original S4X8ES2 becomes unavailable due to inventory constraints, end-of-life status, or supply chain disruptions. STMicroelectronics manufactures compatible alternatives that meet the same electrical and mechanical specifications, enabling design continuity and production flexibility.

Key Parameters

Parameter	S4X8ES2 (Littelfuse)
Voltage - Off State	400 V
Voltage - Gate Trigger (Vgt) (Max)	800 mV
Current - Gate Trigger (Igt) (Max)	50 µA
Voltage - On State (Vtm) (Max)	1.7 V
Current - On State (It (RMS)) (Max)	800 mA
Current - Hold (Ih) (Max)	5 mA
SCR Type	Sensitive Gate
Operating Temperature	-40°C ~ 125°C
Package / Case	TO-226-3, TO-92-3 (TO-226AA)
Mounting Type	Through Hole
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the S4X8ES2 is determined by the following critical parameters:

Voltage Rating (Off State): 400 V minimum
Gate Trigger Voltage (Vgt): 800 mV maximum
On-State Current (It (RMS)): 800 mA rating
SCR Type: Sensitive Gate classification
Package: TO-92-3 through-hole configuration
Operating Temperature Range: -40°C to 125°C
Compliance: ROHS3 Compliant, REACH Unaffected

All substitute parts listed below meet these core electrical and mechanical requirements. Variations in secondary parameters (such as gate trigger current Igt, on-state voltage Vtm, and off-state leakage current) remain within acceptable engineering tolerances for this component category and do not affect functional interchangeability in standard applications.

Parameter Comparison

Parameter	S4X8ES2 (Littelfuse)	P0102DA 1AA3 (STMicroelectronics)	P0102DA 5AL3 (STMicroelectronics)	P0109DA 5AL3 (STMicroelectronics)	XL0840 (STMicroelectronics)
Voltage - Off State	400 V	400 V	400 V	400 V	400 V
Voltage - Gate Trigger (Vgt) (Max)	800 mV	800 mV	800 mV	800 mV	800 mV
Current - Gate Trigger (Igt) (Max)	50 µA	200 µA	200 µA	200 µA	200 µA
Voltage - On State (Vtm) (Max)	1.7 V	1.95 V	1.95 V	1.95 V	1.95 V
Current - On State (It (RMS)) (Max)	800 mA	800 mA	800 mA	800 mA	800 mA
Current - Hold (Ih) (Max)	5 mA	5 mA	5 mA	5 mA	5 mA
Current - Off State (Max)	3 µA	10 µA	10 µA	10 µA	1 µA
SCR Type	Sensitive Gate	Sensitive Gate	Sensitive Gate	Sensitive Gate	Sensitive Gate
Operating Temperature	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C
Package / Case	TO-226-3, TO-92-3	TO-226-3, TO-92-3	TO-226-3, TO-92-3	TO-226-3, TO-92-3	TO-226-3, TO-92-3
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Active	Active	Active	Active	Last Time Buy

Engineering Selection Recommendations

P0102DA 1AA3 (STMicroelectronics, Bulk Packaging): This part is recommended as the primary substitute for the S4X8ES2. It maintains Active product status and meets all critical electrical parameters. The Bulk packaging format is suitable for high-volume production environments. Current inventory availability is 4,848 pieces.

P0102DA 5AL3 (STMicroelectronics, Cut Tape Packaging): This part is functionally equivalent to P0102DA 1AA3 and offers the highest inventory availability at 35,300 pieces. The Cut Tape (CT) packaging with formed leads is optimized for automated assembly processes. Active product status ensures long-term supply continuity.

P0109DA 5AL3 (STMicroelectronics, Cut Tape Packaging): This part meets all substitution criteria and is available in Cut Tape format with 3,567 pieces in stock. Active product status supports ongoing production requirements. The P0109 base product number indicates a variant within the STMicroelectronics sensitive gate SCR family.

XL0840 (STMicroelectronics, Bulk Packaging): This part is electrically compatible with the S4X8ES2 and offers the lowest off-state leakage current (1 µA) among all substitutes. However, its Last Time Buy status indicates this part is approaching end-of-life. Selection of XL0840 should be limited to applications where existing inventory must be consumed or where the superior leakage current specification is critical. Current inventory is 30,100 pieces.

All substitute parts maintain ROHS3 compliance and REACH Unaffected status, ensuring regulatory alignment with the original S4X8ES2.

Frequently Asked Questions (FAQ)

Q: Can P0102DA 1AA3 be used as a direct replacement for S4X8ES2 in existing designs?

A: Yes. P0102DA 1AA3 meets all critical electrical specifications including 400 V off-state voltage, 800 mV gate trigger voltage, and 800 mA RMS on-state current. The TO-92-3 package is mechanically identical. No circuit modifications are required.

Q: What is the difference between P0102DA 5AL3 and P0102DA 1AA3?

A: Both parts are electrically identical. The primary difference is packaging format: P0102DA 1AA3 is supplied in Bulk, while P0102DA 5AL3 is supplied in Cut Tape (CT) with formed leads. P0102DA 5AL3 is optimized for automated pick-and-place assembly, while P0102DA 1AA3 is suitable for manual or bulk handling processes.

Q: Why does P0102DA 5AL3 have higher gate trigger current (Igt) than S4X8ES2?

A: The S4X8ES2 specifies Igt (Max) of 50 µA, while P0102DA 5AL3 specifies 200 µA. Both values remain within the sensitive gate classification and do not affect functional interchangeability. The higher specification in the substitute part represents a broader tolerance band and does not indicate reduced performance in standard applications.

Q: Should XL0840 be selected for new designs?

A: XL0840 is classified as Last Time Buy, indicating it is approaching end-of-life. For new designs, P0102DA 1AA3 or P0102DA 5AL3 are recommended to ensure long-term supply availability and product continuity. XL0840 is suitable only for applications where existing inventory must be utilized or where the superior off-state leakage current (1 µA) is a critical design requirement.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed (P0102DA 1AA3, P0102DA 5AL3, P0109DA 5AL3, and XL0840) are ROHS3 Compliant and REACH Unaffected, matching the compliance status of the original S4X8ES2.

Q: What is the difference between P0102DA 5AL3 and P0109DA 5AL3?

A: Both parts are electrically and mechanically identical. The difference is the base product number: P0102 versus P0109. Both are STMicroelectronics sensitive gate SCR variants rated for 400 V, 800 mA operation. Selection between these parts is based on inventory availability and supplier preference.

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