LH1544AB Solid State Relay - Equivalent & Substitute Parts

Part Overview

The LH1544AB is a solid state relay (SSR) manufactured by Vishay Semiconductor Opto Division, configured as a SPST-NO (Single Pole Single Throw - Normally Open) relay with dual channels in an 8-DIP through-hole package. The device is rated for 40 mA load current at 0-200V AC/DC operation with a maximum on-state resistance of 110 Ohms.

The LH1544AB is classified as obsolete. Equivalent and substitute parts are available from active product lines that maintain compatible electrical and mechanical specifications, enabling direct replacement in existing designs and new applications.

Substiute Parts

LH1544AB

Vishay Semiconductor Opto DivisionIn Stock: 2681LH1544AB Datasheet

Current PartRFQ

VOR2121A8

Vishay Semiconductor Opto DivisionIn Stock: 1014VOR2121A8 Datasheet

DirectRFQ

VOR2121B8

Vishay Semiconductor Opto DivisionIn Stock: 967VOR2121B8 Datasheet

MFR RecommendedRFQ

AQW227N

Panasonic Electric WorksIn Stock: 1362AQW227N Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the LH1544AB is determined by the following critical parameters:

• Circuit Configuration: All substitutes maintain SPST-NO (1 Form A) x 2 dual-channel topology
• Package / Case: Primary substitutes use 8-DIP (0.300", 7.62mm) through-hole package for direct pin compatibility
• Mounting Type: Through-hole mounting is required for mechanical compatibility with existing PCB layouts
• Termination Style: PC Pin termination ensures socket and board compatibility
• Load Voltage Range: Substitutes must support minimum 0-200V operation
• Output Type: AC/DC capability is maintained across all substitutes
• RoHS Compliance: All substitutes maintain ROHS3 compliance for regulatory alignment

Substitutes are grouped into two categories: direct pin-compatible through-hole replacements (VOR2121A8, AQW227N) and surface-mount alternatives (VOR2121B8) for applications where mounting technology transition is acceptable.

Parameter Comparison

Engineering Selection Recommendations

For Direct Through-Hole Replacement (No PCB Modification Required):

VOR2121A8 and AQW227N are pin-compatible through-hole substitutes. Both maintain the 8-DIP (0.300", 7.62mm) package with PC Pin termination, enabling direct socket replacement without PCB layout changes. VOR2121A8 is manufactured by Vishay, the original OEM, and offers increased load current capacity (200 mA vs. 40 mA) and extended voltage rating (250V vs. 200V). AQW227N from Panasonic provides comparable performance with slightly lower on-state resistance (50 Ohms vs. 110 Ohms) and maintains the original 200V load voltage specification.

For Surface-Mount Applications (PCB Redesign Required):

VOR2121B8 is a surface-mount variant using 8-SMD package with gull-wing termination. This option requires PCB layout modification and is suitable only for new designs or board revisions. It provides the same electrical performance as VOR2121A8 with enhanced thermal characteristics typical of surface-mount construction.

Compliance and Availability:

All substitute parts maintain ROHS3 compliance and are classified as active products with confirmed inventory availability. Selection should prioritize through-hole options (VOR2121A8, AQW227N) for retrofit applications to minimize implementation cost and design risk.

Frequently Asked Questions (FAQ)

Q: Can VOR2121A8 directly replace LH1544AB without PCB modification?

A: Yes. VOR2121A8 maintains identical package (8-DIP), mounting type (through-hole), and termination style (PC Pin) as LH1544AB. The device can be inserted into existing sockets without PCB changes. The increased load current rating (200 mA) and voltage range (250V) provide enhanced capability margins.

Q: What is the difference between VOR2121A8 and VOR2121B8?

A: VOR2121A8 uses through-hole mounting (8-DIP with PC Pin termination), while VOR2121B8 uses surface-mount technology (8-SMD with gull-wing termination). Electrical specifications are identical. VOR2121B8 requires PCB redesign and is not suitable for direct socket replacement.

Q: Is AQW227N compatible with existing LH1544AB socket designs?

A: Yes. AQW227N maintains the 8-DIP through-hole package and PC Pin termination, enabling direct socket compatibility. The device is manufactured by Panasonic and provides comparable electrical performance with lower on-state resistance (50 Ohms vs. 110 Ohms).

Q: What are the key electrical differences between the substitutes?

A: VOR2121A8 and VOR2121B8 offer higher load current (200 mA vs. 40 mA) and extended voltage rating (250V vs. 200V). AQW227N maintains the original 200V voltage specification with 50 mA load current. All three substitutes have lower on-state resistance than the original LH1544AB, resulting in reduced power dissipation and improved thermal performance.

Q: Are all substitutes RoHS compliant?

A: Yes. VOR2121A8, VOR2121B8, and AQW227N are all ROHS3 compliant, matching the regulatory status of the obsolete LH1544AB.

Q: Which substitute should be selected for a retrofit application?

A: For retrofit applications requiring no PCB modification, select either VOR2121A8 (Vishay OEM) or AQW227N (Panasonic). Both maintain through-hole mounting and PC Pin termination. VOR2121A8 is recommended when higher current capacity and voltage margin are beneficial. AQW227N is suitable when maintaining the original 200V specification is required.