L4981B Equivalent & Substitute Parts

Part Overview

The L4981B is a Power Factor Correction (PFC) controller integrated circuit manufactured by STMicroelectronics, designed for average current mode operation at 100kHz switching frequency. This device is classified as obsolete, indicating it has been discontinued from active production. The L4981B operates within a 14.5V to 19.5V supply voltage range and is packaged in a 20-DIP through-hole configuration suitable for conventional PCB assembly methods.

Due to its obsolete status, sourcing new original units may present supply chain challenges. Identifying functionally equivalent substitute parts with compatible electrical and mechanical parameters is essential for design continuity and production planning.

Substiute Parts

L4981B

STMicroelectronicsIn Stock: 1265L4981B Datasheet

Current PartRFQ

L4981BD

STMicroelectronicsIn Stock: 2966L4981BD Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the L4981B is determined by strict alignment of the following electrical and mechanical parameters:

Electrical Compatibility Criteria:

• Mode of operation: Average Current
• Switching frequency: 100kHz
• Supply voltage range: 14.5V ~ 19.5V
• Startup current: 100 µA
• Operating temperature range: -40°C ~ 125°C

Mechanical Compatibility Criteria:

• Base product number: L4981
• Regulatory compliance: ROHS3 Compliant, REACH Unaffected

Packaging Consideration: The L4981B is available in 20-DIP through-hole packaging. Substitute parts may utilize alternative package types (such as 20-SOIC surface mount) provided all electrical parameters remain identical. Package selection depends on PCB assembly capabilities and design requirements.

The L4981BD qualifies as a direct electrical substitute, sharing identical functional specifications while offering an alternative surface-mount package option and active product status.

Parameter Comparison

Engineering Selection Recommendations

L4981BD as Primary Substitute:

The L4981BD is the direct electrical equivalent of the L4981B, maintaining identical functional specifications across all critical parameters: average current mode operation, 100kHz switching frequency, 14.5V to 19.5V supply voltage range, and -40°C to 125°C operating temperature range.

Advantages of L4981BD:

• Active product status ensures ongoing availability and supply chain stability
• ROHS3 and REACH compliance maintained
• Identical electrical performance and pin functionality
• Higher inventory availability (2874 Pcs vs. 1237 Pcs for L4981B)

Design Considerations:

The primary difference between L4981B and L4981BD is the package type: L4981B uses 20-DIP through-hole mounting, while L4981BD uses 20-SOIC surface-mount packaging. This distinction requires PCB redesign if transitioning between the two parts. The L4981BD has a higher Moisture Sensitivity Level (MSL 3 vs. MSL 1), requiring controlled storage conditions during handling and assembly.

Selection between these parts depends on manufacturing process capability and PCB design constraints rather than electrical performance.

Frequently Asked Questions (FAQ)

Q: Can the L4981BD directly replace the L4981B without circuit modifications?

A: The L4981BD provides identical electrical functionality and pin configuration to the L4981B. However, the package type differs: L4981B is 20-DIP (through-hole) while L4981BD is 20-SOIC (surface-mount). Direct PCB-level substitution requires compatible footprint design. Schematic-level functionality remains unchanged.

Q: What is the significance of the different Moisture Sensitivity Levels (MSL)?

A: The L4981B has MSL 1 (Unlimited), allowing indefinite shelf storage without moisture absorption concerns. The L4981BD has MSL 3 (168 Hours), requiring that the component be used within 168 hours of package opening under controlled humidity conditions. This affects storage, handling, and assembly procedures but does not impact electrical performance.

Q: Are there any compliance or regulatory differences between these parts?

A: Both the L4981B and L4981BD maintain identical ROHS3 compliance and REACH Unaffected status. No regulatory or compliance barriers exist for substitution from a compliance perspective.

Q: Why is the L4981B listed as obsolete?

A: Obsolete status indicates the L4981B has been discontinued from active production by STMicroelectronics. The L4981BD, sharing the same base product number (L4981) and electrical specifications, represents the active continuation of this product line in surface-mount packaging.

Q: What are the key electrical parameters that define substitution eligibility?

A: Substitution eligibility is determined by: average current mode operation, 100kHz switching frequency, 14.5V to 19.5V supply voltage range, 100 µA startup current, and -40°C to 125°C operating temperature range. Any part meeting these specifications with the L4981 base product number qualifies as an electrical equivalent.

Q: Can the L4981BD be used in existing L4981B designs without performance degradation?

A: Electrical performance is identical between the two parts. Performance degradation does not occur from an electrical standpoint. PCB layout modifications are required to accommodate the different package footprint (20-DIP vs. 20-SOIC).