LNK305 PMIC Datasheet, Features, Pinout, and Applications

The LNK305 is a highly integrated Power Management Integrated Circuit (PMIC) from Power Integrations designed for offline switch-mode power supplies. With its integrated control, switching, and protection features, the LNK305 simplifies power supply design while ensuring high efficiency and reliability. It is widely used in consumer electronics, industrial equipment, and appliances where compact and cost-effective power solutions are required.

Overview of LNK305

The LinkSwitch-TN range is meticulously engineered to supplant traditional linear and capacitor-driven (cap dropper) non-isolated power supply units for applications requiring up to 360 mA of output current. These devices are designed to be as cost-effective as their predecessors yet vastly superior in terms of performance and energy efficiency. Each LinkSwitch-TN unit combines several critical features into one compact, monolithic IC: a 700 V power MOSFET, an oscillator, a basic On/Off control system, a high-voltage switched current source, frequency jittering, and comprehensive protection mechanisms, including cycle-by-cycle current limiting and thermal shutdown. Power for startup and operation is directly drawn from the DRAIN pin voltage, which negates the need for a separate bias power supply in buck or flyback configurations. Additionally, these devices incorporate an automatic restart feature in the LNK305 model to securely control output power under abnormal conditions like short circuits or open loops, thereby minimizing the number of components and reducing costs associated with system-level load protection. The inclusion of an internal supply allows for the optional use of a non-safety grade optocoupler as a level shifter to improve line and load regulation in buck and buck-boost converters.

The LNK305 is a member of the LinkSwitch®-TN family of ICs designed for non-isolated, offline power supplies. It combines a high-voltage power MOSFET, oscillator, and control logic into a single package, enabling efficient step-down conversion from AC mains to low-voltage DC. The LNK305 features advanced protection mechanisms, including thermal shutdown, current limiting, and overvoltage protection, making it ideal for robust and safe power supply designs.

LNK305 Feature

Efficient Alternative to Linear and Cap Dropper Systems

• The most cost-effective, minimal-component buck converter is available.
• Integrated auto-restart functionality protects against shorts and open circuits, reducing the need for additional external components.
• The LNK302 model offers a simpler control system without auto-restart, optimizing for an extremely low-cost setup.
• Operates at 66 kHz with precise current limitations, compatible with standard 1 mH inductors for outputs up to 120 mA.
• Exhibits minimal deviation due to tight manufacturing tolerances and insignificant temperature influence.
• A high breakdown voltage of 700 V ensures robust surge protection.
• Frequency jittering significantly lowers electromagnetic interference by about 10 dB, minimizing the need for extensive EMI filtering.
• Features a high thermal shutdown threshold (+135 °C minimum).

Superior Performance Compared to Discrete and Passive Alternatives

• Compatible with buck, buck-boost, and flyback designs.
• Ensures robust system-level protection against thermal overload, output shorts, and open control loops.
• Provides exceptional regulation of both line and load under standard conditions.
• Offers high response speed, enabling rapid activation without voltage overshoot.
• Current limit functionality effectively dampens line noise.
• Accommodates a universal input voltage range from 85 VAC to 265 VAC.
• Incorporates built-in current limitations and hysteretic thermal safety.
• Outperforms passive configurations in efficiency and power factor.
• Fully compatible with surface-mount technology manufacturing.

EcoSmart™ – Optimal Energy Efficiency

• In a self-powered buck topology, it typically consumes just 50/80 mW at 115/230 VAC input when idle (with Opto feedback).
• In a flyback setup with an external bias, power consumption is typically only 7/12 mW at 115/230 VAC input under no-load conditions.
• Complies with the regulations of the California Energy Commission (CEC), Energy Star, and EU standards for energy efficiency.

LNK305 Pinout

Pin Functional Description

DRAIN (D) Pin:

This pin serves as the connection point for the Power MOSFET's drain. It supplies the necessary operating current for both initial startup and ongoing steady-state operations.

BYPASS (BP) Pin:

This pin connects to an external 0.1 µF bypass capacitor, essential for stabilizing the internally generated 5.8 V power supply.

FEEDBACK (FB) Pin:

In regular use, this pin regulates the switching behavior of the Power MOSFET. The switching process is halted once the current flowing into this pin exceeds 49 µA.

SOURCE (S) Pin:

Connected to the source terminal of the Power MOSFET, this pin also acts as the common ground reference for both the BYPASS and FEEDBACK pins.

Absolute Maximum Ratings

LNK305 Application

Appliances and Timers

The LNK305 is extensively utilized in the design of household appliances and timing devices due to its efficiency and reliability. In appliances, this component can be found in the control systems of washing machines, microwave ovens, and air conditioners, where it helps manage power supply and ensures devices operate smoothly under varying electrical conditions. For timers, the LNK305 contributes to the precision and durability of these devices. It is instrumental in applications such as programmable digital clocks, automated sprinkler systems, and other time-sensitive controls, where maintaining accurate timing is crucial.

LED Drivers and Industrial Controls

In the realm of LED lighting, the LNK305 is critical for developing drivers that ensure the stable and efficient operation of LEDs. It regulates the power delivered to the LED arrays, optimizing light output and prolonging the lifespan of the lighting system. This is particularly important in environments requiring robust lighting solutions, such as commercial buildings and outdoor areas. For industrial controls, the LNK305 enhances the functionality and reliability of systems involved in manufacturing and processing. It is used in the control panels of heavy machinery, automated assembly lines, and sensor-based monitoring systems, where it helps maintain operational consistency and safety.

LNK305 Package

The LNK305 is available in compact 8-pin DIP, SMD, and SO packages, designed for ease of integration into PCB layouts. These packages support both through-hole and surface-mount assembly, making the IC compatible with a variety of manufacturing processes and application requirements.

• PDIP-8B (P Package)

• SMD-8B (G Package)

• SO-8C (D Package)

LNK305 Manufacturer

Power Integrations, a leading provider of high-efficiency power conversion ICs, manufactures the LNK305. Power Integrations is known for its innovative solutions that simplify power supply design and improve energy efficiency in consumer, industrial, and appliance applications.

LNK305 Datasheet

The LNK305 datasheet provides detailed technical specifications, including electrical characteristics, pin configurations, and application design guidelines. Engineers can refer to the datasheet for optimizing the integration of the LNK305 into their systems, ensuring efficient and reliable power supply designs.

LNK305 vs. Other PMICs

• LNK305 vs. LNK306: The LNK306 is a higher power variant in the LinkSwitch-TN family, delivering up to 10W. While the LNK305 is optimized for low-power applications, the LNK306 provides additional headroom for higher power requirements.
• LNK305 vs. VIPer22A: The VIPer22A from STMicroelectronics is another high-voltage PMIC for offline applications. However, the LNK305's simplified design and integrated features make it a more cost-effective solution for low-power designs.
• LNK305 vs. LM2596: The LM2596 is a buck regulator IC for DC-DC conversion, whereas the LNK305 is designed for offline AC-DC applications, offering integrated high-voltage operation.

Popular LNK305 ICs

Conclusion

The LNK305 PMIC is a reliable, energy-efficient solution for low-power, offline AC-DC power supplies. With its integrated MOSFET, protection features, and compact package, the LNK305 simplifies power supply design and reduces overall costs. Its high efficiency and universal input voltage compatibility make it a versatile choice for applications in consumer electronics, appliances, industrial systems, and LED lighting.

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