STMicroelectronics L4984D

The L4984D is a current-mode Power Factor Correction (PFC) controller developed by STMicroelectronics. It operates using line-modulated fixed-off-time (LM-FOT) control, enabling fixed-frequency operation for boost PFC converters in continuous conduction mode (CCM). This controller is packaged in a 10-pin SSOP package and is designed to provide a low-cost solution for CCM-operated boost PFC pre-regulators. It is compliant with EN61000-3-2 and JEIDA-MITI standards and is suitable for power supplies ranging from a few hundred watts to over 1 kW.

The L4984D features a highly linear multiplier that reduces crossover distortion of the AC input current, allowing for wide-range mains operation with low Total Harmonic Distortion (THD). The output voltage is controlled by a voltage-mode error amplifier and an accurate internal voltage reference. The device also includes various protection features such as overvoltage protection, feedback loop failure protection, inductor saturation protection, and AC brownout detection.

The L4984D is energy-efficient and supports remote on/off control, making it suitable for applications that comply with the latest energy-saving requirements like Blue Angel, ENERGY STAR, and Energy 2000.

• Line-modulated fixed-off-time (LM-FOT) control of CCM-operated PFC pre-regulators
• Proprietary LM-FOT modulator for nearly fixed-frequency operation
• Proprietary multiplier design for minimum THD of AC input current
• Fast “bi-directional” input voltage feedforward (1/V2 correction)
• Accurate adjustable output overvoltage protection
• Protection against feedback loop failure (latched shutdown)
• Inductor saturation protection
• AC brownout detection
• Digital leading-edge blanking on current sense
• Soft-start
• 600 mA source and 800 mA sink current totem pole gate driver

The L4984D is suitable for various high-power applications, including:

• PFC pre-regulators for IEC61000-3-2 and JEIDA-MITI compliant Switch-Mode Power Supplies (SMPS) exceeding 1 kW
• Desktop PCs, servers, and web servers
• Industrial power supplies requiring high efficiency and compliance with energy-saving standards like Blue Angel, ENERGY STAR, and Energy 2000

1. What is the primary function of the L4984D?

   The L4984D is a current-mode Power Factor Correction (PFC) controller operating with line-modulated fixed-off-time (LM-FOT) control.

2. What package type does the L4984D come in?

   The L4984D comes in a 10-pin SSOP package.

3. What is the operating temperature range of the L4984D?

   The operating temperature range is from -25 °C to 125 °C.

4. What are the key protection features of the L4984D?

   The key protection features include overvoltage protection, feedback loop failure protection, inductor saturation protection, and AC brownout detection.

5. How does the L4984D improve line transient response?

   The L4984D uses a proprietary “bi-directional” input voltage feedforward (1/V2 correction) technique to improve line transient response.

6. What is the accuracy of the internal reference voltage?

   The internal reference voltage has an accuracy of 1% at Tj = 25 °C.

7. What is the current capability of the gate driver output?

   The gate driver output is capable of -600 mA source and +800 mA sink current.

8. What standards does the L4984D comply with?

   The L4984D complies with EN61000-3-2 and JEIDA-MITI standards.

9. What energy-saving standards does the L4984D support?

   The L4984D supports energy-saving standards like Blue Angel, ENERGY STAR, and Energy 2000.

10. How does the L4984D handle brownout conditions?

    The L4984D has an AC brownout detection feature that shuts down the IC and reduces consumption during brownout conditions.

11. What is the purpose of the soft-start feature in the L4984D?

    The soft-start feature limits peak current and extends off-time to prevent flux runaway in the initial cycles.