RDK-138

RDK-138 is specifically designed to replace all linear and capacitor-fed (cap dropper) non-isolated power supplies in the under 170mA output current range at equal system cost while offering much higher performance and energy efficiency. RDK-138 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 fly back converters. The fully integrated auto-restart circuit in the RDK-138 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 non safety graded optocoupler acting as a level shifter to further enhance line and load regulation performance in buck and buck-boost converters, if required.

• Cost Effective Linear/Cap Dropper Replacement
  • Lowest cost and component count buck converter solution
  • Fully integrated auto-restart for short-circuit and open loop fault protection - saves external component costs
  • LNK302 uses a simplified controller without auto-restart for very low system cost
  • 66 kHz operation with accurate current limit - allows low cost off-the-shelf 1 mH inductor for up to 120 mA output current
  • Tight tolerances and negligible temperature variation
  • High breakdown voltage of 700 V provides excellent input surge withstand
  • Frequency jittering dramatically reduces EMI (~10 dB)
  • Minimizes EMI filter cost
  • High thermal shutdown temperature (+135 °C minimum)
• Much Higher Performance Over Discrete Buck and Passive Solutions
  • Supports buck, buck-boost and fly back topologies
  • System level thermal overload, output short-circuit and open control loop protection