L4981A

Overview

The L4981A is a fixed-frequency average current mode Power Factor Correction (PFC) controller manufactured by STMicroelectronics. It operates at a switching frequency of 115 kHz and supports universal AC input voltages ranging from 85V to 265V without line switching requirements. The device achieves a power factor up to 0.99 with line current distortion limited to less than 5%. Key electrical parameters include a supply voltage range of 12V to 19V, a typical start-up current of 0.3mA, and an operating temperature range from -40°C to 125°C. It integrates overvoltage and overcurrent protection features.

Feature Summary

• Fixed frequency operation utilizing average current mode PWM control to maintain sinusoidal line current without slope compensation.
• Integrated high-current bipolar and DMOS totem-pole output for direct MOSFET gate driving.
• Built-in protections including overvoltage detection, programmable overcurrent limits, and under-voltage lockout with hysteresis.
• Synchronization capability via dedicated I/O pin allowing master or slave configuration with downstream controllers.

Applications

• High-efficiency AC-DC pre-regulators for server and telecom power supplies
• Universal input power factor correction stages in consumer electronics
• Bridgeless PFC topologies for mid-range power applications

Procurement Notes

Verify the specific package variant required, as the L4981A family includes both DIP-20 and SOIC-20 options. Confirm whether tube or tape-and-reel packaging is needed for production lines. Ensure compatibility with existing board layouts when substituting older revisions. Check for RoHS compliance status if environmental regulations apply to the end product. Validate that the fixed-frequency specification meets EMI filter design constraints.

Selection Notes

Select the L4981A when a fixed switching frequency is required to optimize input filter size compared to line-modulated alternatives. This model is suitable for designs needing average current mode control for lower noise sensitivity. Consider the integrated gate driver capabilities and protection features to reduce external component count. Evaluate synchronization needs if interfacing with secondary PWM controllers in multi-stage power systems.

Part Context

The L4981A belongs to the L4981 series, which also includes the L4981B featuring line-modulated frequency operation. Both variants share similar control architectures but differ in frequency modulation strategies. The L4981A specifically targets applications where constant frequency operation simplifies electromagnetic interference filtering. It serves as a foundational component for continuous conduction mode boost PFC converters.

Replacement Considerations

The L4981BD is listed as a similar replacement option. Verify package compatibility and functional equivalence before substitution. Note that the L4981A itself may be obsolete in some regions; check current availability status.