UC3855BN Equivalent & Substitute Parts

Part Overview

The UC3855BN is a Power Factor Correction (PFC) controller IC manufactured by Texas Instruments, designed for average current mode operation at 500kHz switching frequency. This device is classified as Last Time Buy, indicating end-of-life status with limited availability. The UC3855BN operates in the 10.5V to 20V supply range and is packaged in a 20-pin DIP through-hole configuration, making it suitable for legacy and industrial power management applications requiring PFC functionality.

Due to its Last Time Buy status, identifying functionally compatible substitute components is essential for design continuity and long-term supply chain planning.

Substiute Parts

UC3855BN

Texas InstrumentsIn Stock: 3236UC3855BN Datasheet

Current PartRFQ

UCC28180DR

Texas InstrumentsIn Stock: 25251UCC28180DR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the UC3855BN is determined by the following critical parameters:

• Functional Category: Both parts must be PFC controller ICs from Texas Instruments
• Control Mode: The UC3855BN operates in average current mode; the UCC28180DR operates in continuous conduction (CCM) mode, representing a different control topology
• Switching Frequency Range: UC3855BN operates at fixed 500kHz; UCC28180DR operates across 18kHz ~ 250kHz range
• Supply Voltage Compatibility: UC3855BN requires 10.5V ~ 20V; UCC28180DR requires 21V nominal
• Package Type: UC3855BN uses 20-DIP through-hole; UCC28180DR uses 8-SOIC surface mount
• Regulatory Compliance: Both devices are ROHS3 compliant and REACH unaffected

The UCC28180DR is identified as a manufacturer-recommended substitute, though it operates under different electrical parameters and requires different mounting and board layout considerations.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The UC3855BN is Last Time Buy, while the UCC28180DR is Active. This status difference reflects ongoing manufacturer support and availability for the UCC28180DR.

Regulatory Compliance: Both devices meet ROHS3 and REACH requirements, ensuring compliance with current environmental standards.

Supply Chain Availability: The UCC28180DR has significantly higher inventory availability (25,200 pcs) compared to the UC3855BN (3,205 pcs), supporting long-term design continuity.

Functional Differences: The UC3855BN and UCC28180DR employ different control topologies (average current versus continuous conduction mode) and operate across different frequency ranges. These differences require circuit topology evaluation and may necessitate design modifications to peripheral components and control feedback networks.

Packaging and Assembly: Substitution requires transition from through-hole to surface-mount technology, affecting PCB layout, assembly processes, and manufacturing capabilities.

Frequently Asked Questions (FAQ)

Q: Can the UCC28180DR directly replace the UC3855BN without circuit modifications?

A: No. The UCC28180DR operates in continuous conduction (CCM) mode while the UC3855BN uses average current mode. These control topologies require different feedback network designs and may require modifications to power stage components and control circuitry.

Q: What are the key electrical differences between these parts?

A: The UC3855BN operates at fixed 500kHz with 10.5V ~ 20V supply range, while the UCC28180DR operates across 18kHz ~ 250kHz with 21V supply requirement. The UCC28180DR also features lower startup current (75 µA versus 150 µA) and wider operating temperature range (-40°C ~ 125°C versus 0°C ~ 70°C).

Q: Does the package change from 20-DIP to 8-SOIC affect board design?

A: Yes. The transition from through-hole to surface-mount packaging requires PCB redesign, different assembly processes, and modified thermal management considerations. The 8-SOIC package is significantly smaller than the 20-DIP package.

Q: Are both devices compliant with current environmental regulations?

A: Yes. Both the UC3855BN and UCC28180DR are ROHS3 compliant and REACH unaffected, meeting current environmental standards.

Q: Why is the UCC28180DR recommended as a substitute if it requires design changes?

A: The UCC28180DR is manufacturer-recommended based on functional PFC controller category and regulatory compliance. However, substitution requires engineering evaluation of control topology differences and circuit adaptation to ensure proper system performance.