L4985A

Overview

The L4985A is a Continuous Conduction Mode (CCM) Power Factor Correction (PFC) controller designed for boost converters. It features an integrated 800V high-voltage startup block with active X-capacitor discharge, eliminating the need for parallel resistors to meet safety standards like IEC 61010-1 and IEC 62368-1. The device utilizes a proprietary multiplier emulator and THD optimizer to ensure minimal total harmonic distortion across all operating conditions. It operates at a quasi-fixed frequency of 65 kHz, providing a low-component-count solution for power supplies ranging from hundreds to several thousand watts.

Feature Summary

• Integrated 800V high-voltage startup circuit with active input filter capacitor discharge
• Proprietary multiplier emulator ensuring minimal line current total harmonic distortion
• Quasi-fixed frequency operation at 65 kHz using dedicated off-time modulator
• Comprehensive protection mechanisms including feedback loop fault, OVP, OCP, and inductor saturation

Applications

• SMPS pre-regulators compliant with EN61000-3-2 and JEIDA-MITI standards
• Medical SMPS designs requiring specific output regulation during mains sags
• Power supplies ranging from 150 W to several kW

Procurement Notes

Verify the suffix 'A' against official STMicroelectronics documentation to confirm it denotes the 65 kHz switching frequency variant. Ensure compatibility with required thermal management for SO-8 packages. Confirm that the specific revision matches the intended safety certifications such as IEC 61010-1 or IEC 62368-1 compliance requirements for your application design.

Selection Notes

Select this component when designing CCM PFC stages requiring high-voltage startup without external discharge resistors. It is suitable for applications demanding low THD performance across wide load ranges. Consider the 65 kHz frequency for balancing EMI filtering complexity and magnetic component size. Evaluate the SO-8 package constraints against available PCB space and thermal dissipation capabilities.

Part Context

The L4985 belongs to STMicroelectronics' family of CCM PFC controllers. It shares architectural similarities with the L4986 but lacks the power good signal output found in the latter. This series targets high-efficiency power factor correction solutions, offering integrated features that reduce external component count compared to traditional discrete implementations.

Replacement Considerations

The L4985B serves as a functional substitute within the same package if a 130 kHz switching frequency is acceptable. Verify pinout compatibility and control loop stability when transitioning between frequency variants.