LNK306DG-TL Integrated Circuits (ICs)

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1. Description

LinkSwitch-TN is specifically designed to replace all linear and capacitor-fed (cap dropper) non-isolated power supplies in the under 360 mA output current range at equal system cost while offering much higher performance and energy efficiency. LinkSwitch-TN devices integrate a 700 V power MOSFET, oscillator, simple On/Off control scheme, a high-voltage switched current source, frequency jittering, cycle-by-cycle current limit and thermal shutdown circuitry onto a monolithic IC. The start-up and operating power are derived directly from the voltage on the DRAIN pin, eliminating the need for a bias supply and associated circuitry in buck or flyback converters. The fully integrated auto-restart circuit in the LNK304-306 safely limits output power during fault conditions such as short-circuit or open loop, reducing component count and system-level load protection cost. A local supply provided by the IC allows use of a nonsafety graded optocoupler acting as a level shifter to further enhance line and load regulation performance in buck and buck-boost converters, if required.

2. Feature

    1. Lowest cost and component count buck converter solution 

    2. Fully integrated auto-restart for short-circuit and open loop fault protection – saves external component costs

    3. LNK302 uses a simplified controller without auto-restart for very low system cost

    4. 66 kHz operation with accurate current limit – allows low cost off-the-shelf 1 mH inductor for up to 120 mA output current

    5. Tight tolerances and negligible temperature variation

    6. High breakdown voltage of 700 V provides excellent input surge withstand

    7. Frequency jittering dramatically reduces EMI (~10 dB)

    8. Minimizes EMI filter cost

    9. High thermal shutdown temperature (+135 °C minimum)

3. Product Features

    1. Supports buck, buck-boost and flyback topologies

    2. System Level Thermal Overload, Output Shorts and Opens Control loop protection

    3. Excellent line and load regulation even in typical configurations

    4. High bandwidth provides fast turn-on without overshoot

    5. Current limiting operation suppresses line ripple

    6. Universal input voltage range (85 VAC to 265 VAC)

    7. Built-in current limit and hysteretic thermal protection

    8. More efficient than passive solutions

    9. Higher power factor than capacitor powered solutions

  10. Fully manufacturable in SMD

4. Applications

    1. Appliances and timers

    2. LED drivers and industrial controls

5. Pin configuration

6. Pin Functional Description

    1. DRAIN (D) Pin: Power MOSFET drain connection. Provides internal operating current for both start-up and steady-state operation.

    2. BYPASS (BP) Pin: Connection point for a 0.1 mF external bypass capacitor for the internally generated 5.8 V supply.

    3. FEEDBACK (FB) Pin: During normal operation, switching of the power MOSFET is controlled by this pin. MOSFET switching is terminated when a current greater than 49 µA is delivered into this pin.

    4. SOURCE (S) Pin: This pin is the power MOSFET source connection. It is also the ground reference for the BYPASS and FEEDBACK pins.