Overview
The L4981A, produced by STMicroelectronics, is a power factor corrector (PFC) pre-regulator integrated circuit designed to achieve high power factor correction up to 0.99. Realized in BCD 60II technology, this IC contains all the necessary control functions for designing high-efficiency power supplies with sinusoidal line current consumption. The L4981A can operate in systems with mains voltages between 85V to 265V without any line switch, offering the flexibility to work at a fixed frequency. It integrates various features such as a power MOSFET gate driver, precise voltage reference, error amplifier, under-voltage lockout, current sense, and soft start, making it a comprehensive solution for power supply design.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Operating Supply Voltage (VCC) | 12V to 19.5V | V |
| Operating Ambient Temperature | -40 to 125 °C | °C |
| Storage Temperature | -55 to 150 °C | °C |
| Power Dissipation at Tamb = 70°C (DIP20) | 1 W | W |
| Power Dissipation at Tamb = 70°C (SO20) | 0.6 W | W |
| Gate Driver Output Peak Current (t = 1µs) | SINK: 2 A, SOURCE: 1.5 A | A |
| Initial Oscillator Frequency Accuracy | 85 to 115 KHz | KHz |
| Overvoltage Protection Threshold | 5.1 V (typ) ± 20 mV | V |
| Overcurrent Protection Threshold | Programmable using external resistors | - |
Key Features
- Precise 2% on-chip reference externally available
- Overvoltage and overcurrent protection
- Soft start
- Low start-up current (0.3mA typical)
- High current bipolar and DMOS totem pole output
- Control boost PWM up to 0.99 power factor
- Universal input mains (85V to 265V)
- Limit line current distortion to < 5%
- Average current mode PWM for minimum noise sensitivity
- Under voltage lockout with hysteresis and programmable turn-on threshold
- Feed forward line and load regulation
Applications
The L4981A is suitable for a wide range of high-efficiency power supply applications, including:
- Switch-mode power supplies requiring high power factor correction
- Industrial power supplies
- Medical equipment power supplies
- Aerospace and defense power supplies
- High-power consumer electronics
Q & A
- What is the primary function of the L4981A IC?
The primary function of the L4981A IC is to provide power factor correction (PFC) to achieve a high power factor up to 0.99 in power supply systems.
- What are the operating voltage ranges for the L4981A?
The L4981A operates with mains voltages between 85V to 265V and an operating supply voltage (VCC) of 12V to 19.5V.
- What types of protection does the L4981A offer?
The L4981A offers overvoltage and overcurrent protection, as well as under-voltage lockout with hysteresis and programmable turn-on threshold.
- How does the L4981A manage line current distortion?
The L4981A limits line current distortion to less than 5% using average current mode PWM.
- What is the significance of the soft start feature in the L4981A?
The soft start feature helps in reducing the inrush current during startup, ensuring a smooth and controlled power-up sequence.
- Can the L4981A be used in high-temperature environments?
- How is the oscillator frequency controlled in the L4981A?
The oscillator frequency can be controlled using external resistors and capacitors connected to the ROSC and COSC pins.
- What is the purpose of the SYNC pin in the L4981A?
The SYNC pin is used for synchronization and can operate as both an input and output, allowing synchronization with other devices.
- How is the overcurrent level programmed in the L4981A?
The overcurrent level can be programmed using a simple resistor for the L4981A, and for better precision, an external divider can be used for the L4981B.
- What are some typical applications of the L4981A?
The L4981A is typically used in switch-mode power supplies, industrial power supplies, medical equipment, aerospace and defense, and high-power consumer electronics.
