Zero¹ Loss Automatic X Capacitor Rapid Discharge IC

Figure 1. Typical Application – Not a Simplified Circuit.

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Product Details

When AC voltage is applied, CAP300DG blocks current flow in the X capacitor safety discharge resistors, reducing the power loss to less than 5 mW, or essentially zero¹ at 230 VAC. When AC voltage is disconnected, CAP300DG automatically discharges the X capacitor by connecting the series discharge resistors. This operation allows total flexibility in the choice of the X capacitor to optimize differential mode EMI filtering and reduce inductor costs, with no change in power consumption.

Designing with CAP300DG is simply a matter of selecting the appropriate external resistor values for the X capacitor value being used to achieve the necessary time constant. The simplicity and ruggedness of the two terminal CAP300DG IC makes it an ideal choice in systems designed to meet ErP Lot 6 requirements.


Key Features

  • Meets IEC 60335 X capacitor discharge of <34 V in <1 sec
  • One part to cover X capacitor values from 100 nF to 6 mF
  • Blocks current through X capacitor discharge resistors when AC voltage is connected
  • Automatically discharges X capacitors through discharge resistors when AC is disconnected
  • Simplifies EMI filter design – larger X capacitor allows smaller inductive components with no change in consumption
  • Only two terminals – meets safety standards for use before or after system input fuse
  • >4 mm creepage on package and PCB
  • Self supplied – no external bias required
  • High common mode surge immunity – no external ground connection
  • High differential surge withstand – 1000 V internal MOSFETs
  • NEMKO and CB certified

Component Table

Product³BVDSSTotal X CapacitanceTotal Series Resistance²
(R1 + R2)
CAP300DG1000 V100 nF to 6 µF54 KΩ Minimum


  1. IEC 62301 clause 4.5 rounds standby power use below 5 mW to zero.
  2. Values are nominal. RC time constant is <1 second.
  3. Packages: D: SO-8.

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