Zero Loss Automatic X Capacitor Discharge IC

Figure 1. Typical Application – Not a Simplified Circuit.

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When AC voltage is applied, CAP200DG blocks current flow in the X capacitor safety discharge resistors, reducing the power loss to less than 5 mW, or essentially zero at 230 VAC. When AC voltage is disconnected, CAP200DG 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 CAP200DG 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 CAP200DG IC makes it an ideal choice in systems designed to meet EuP Lot 6 requirements.


Key Features

  • 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 certification

Component Selection Guide

Product2BVDSSMax Total X CapacitanceTotal
(R1 + R2)
CAP200DG 1000 V 100 nF to 6 µF 7.5 MΩ to 142 kΩ


  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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