L4X3 TRIAC Equivalent & Substitute Parts

Part Overview

The L4X3 is a Logic - Sensitive Gate TRIAC manufactured by Littelfuse Inc., rated for 400 V off-state voltage and 800 mA on-state current in a DO-214AA surface mount package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The L4X3 operates within a temperature range of -40°C to 110°C and features a maximum gate trigger voltage of 1.3 V with 3 mA gate trigger current. Its sensitive gate configuration makes it suitable for low-power switching applications requiring minimal gate drive.

Key Parameters

Parameter	Value
Triac Type	Logic - Sensitive Gate
Voltage - Off State	400 V
Current - On State (It (RMS)) (Max)	800 mA
Voltage - Gate Trigger (Vgt) (Max)	1.3 V
Current - Gate Trigger (Igt) (Max)	3 mA
Current - Hold (Ih) (Max)	5 mA
Operating Temperature	-40°C ~ 110°C (TJ)
Mounting Type	Surface Mount
Package / Case	DO-214AA, SMB (3 Leads), Compak
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the L4X3 is determined by the following critical parameters:

Triac Type: Logic - Sensitive Gate configuration
Voltage - Off State: Minimum 400 V rating
Current - On State: Minimum 800 mA capability
Gate Trigger Characteristics: Vgt ≤ 1.3 V and Igt ≤ 3 mA
Mounting Type: Surface Mount
Package Compatibility: DO-214AA or equivalent footprint

Two substitute categories are identified:

Direct Equivalent (L4X3RP): Identical electrical specifications and packaging, differing only in product status (Active vs. Obsolete) and packaging format (Tape & Reel).

Higher-Rated Substitutes (BT131W-600,135 and Z0103MN,135): These parts exceed the L4X3 specifications in voltage rating (600 V) and current capacity (1 A), maintaining compatible gate trigger characteristics and surface mount packaging. These substitutes are suitable where higher voltage or current margins are acceptable.

Parameter Comparison

Parameter	L4X3	L4X3RP	BT131W-600,135	Z0103MN,135
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	WeEn Semiconductors	WeEn Semiconductors
Product Status	Obsolete	Active	Active	Active
Triac Type	Logic - Sensitive Gate	Logic - Sensitive Gate	Logic - Sensitive Gate	Logic - Sensitive Gate
Voltage - Off State	400 V	400 V	600 V	600 V
Current - On State (It (RMS)) (Max)	800 mA	800 mA	1 A	1 A
Voltage - Gate Trigger (Vgt) (Max)	1.3 V	1.3 V	1.5 V	1.3 V
Current - Gate Trigger (Igt) (Max)	3 mA	3 mA	3 mA	3 mA
Current - Hold (Ih) (Max)	5 mA	5 mA	5 mA	7 mA
Operating Temperature (TJ)	-40°C ~ 110°C	-40°C ~ 110°C	125°C	125°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	DO-214AA, SMB (3 Leads)	DO-214AA, SMB (3 Leads)	TO-261-4, TO-261AA	TO-261-4, TO-261AA
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	RoHS Compliant	RoHS Compliant

Engineering Selection Recommendations

L4X3RP is the primary substitute for direct replacement. It maintains identical electrical specifications and temperature range while offering active product status and improved availability (3900 pcs in stock vs. 903 pcs for L4X3). Both parts are ROHS3 compliant and use the same DO-214AA package footprint.

BT131W-600,135 and Z0103MN,135 are suitable substitutes where circuit design permits higher voltage and current ratings. Both parts are active products with RoHS compliance and extended operating temperature to 125°C. The package footprint differs (TO-261-4 vs. DO-214AA), requiring PCB layout modification. Z0103MN,135 maintains the 1.3 V gate trigger voltage specification identical to L4X3, while BT131W-600,135 specifies 1.5 V maximum.

Selection should prioritize L4X3RP for form-fit-function replacement. Higher-rated alternatives require circuit validation and PCB redesign due to package differences.

Frequently Asked Questions (FAQ)

Q: Can L4X3RP be used as a direct replacement for L4X3?

A: Yes. L4X3RP is electrically and mechanically identical to L4X3, with the same DO-214AA package, voltage rating (400 V), current rating (800 mA), and gate trigger specifications. The primary difference is product status (Active vs. Obsolete) and packaging format (Tape & Reel).

Q: What are the key differences between L4X3 and the higher-rated substitutes?

A: BT131W-600,135 and Z0103MN,135 provide 600 V off-state voltage and 1 A on-state current, compared to L4X3's 400 V and 800 mA. Both use different packages (TO-261-4 vs. DO-214AA), requiring PCB layout changes. Gate trigger characteristics remain compatible for sensitive gate applications.

Q: Are package changes required when using BT131W-600,135 or Z0103MN,135?

A: Yes. BT131W-600,135 and Z0103MN,135 use TO-261-4 (TO-261AA) packages, while L4X3 uses DO-214AA. PCB footprint modification is necessary. L4X3RP uses the same DO-214AA package and requires no layout changes.

Q: Do all substitute parts meet RoHS compliance?

A: Yes. L4X3RP is ROHS3 compliant. BT131W-600,135 and Z0103MN,135 are RoHS compliant. All parts meet environmental regulatory requirements.

Q: What is the temperature operating range difference?

A: L4X3 and L4X3RP operate from -40°C to 110°C. BT131W-600,135 and Z0103MN,135 extend to 125°C maximum junction temperature, providing wider thermal margin in high-temperature applications.

Q: Can higher-rated parts be used in applications designed for L4X3?

A: Yes, provided circuit design permits. Higher voltage and current ratings provide design margin. However, package differences require PCB redesign. Gate trigger specifications remain compatible for sensitive gate switching applications.

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