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RF filter for an active medical device (AMD) for handling high RF power induced in an associated implanted lead from an external RF field

  • US 9,014,808 B2
  • Filed: 02/23/2014
  • Issued: 04/21/2015
  • Est. Priority Date: 03/01/2011
  • Status: Active Grant
First Claim
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1. An EMI broadband lowpass filtered hermetically sealed feedthrough assembly for an active implantable medical device, the feedthrough assembly including at least one capacitor configured for handling high power by a low equivalent series resistance (ESR), the feedthrough assembly comprising:

  • a) a conductive ferrule;

    b) an insulator hermetically sealed to the conductive ferrule;

    c) a conductor hermetically sealed and disposed through the insulator between a body fluid side and a device side and in a non-conductive relation with the conductive ferrule;

    d) a broadband lowpass capacitor disposed on the device side and configured to be installed inside an electromagnetically shielded and hermetic conductive housing of an active implantable medical device, the capacitor comprising a first and second end metallization, wherein the first end metallization is connected to at least ten active electrode plates and wherein the second end metallization is connected to at least ten ground electrode plates, wherein the at least ten active electrode plates are interleaved and disposed parallel to the at least ten ground electrode plates in a capacitor dielectric, wherein the capacitor dielectric has a dielectric constant of less than 200;

    e) an active electrical connection electrically coupling the first end metallization to the conductor; and

    f) a ground electrical connection electrically coupling the second end metallization to the conductive ferrule;

    g) wherein the capacitor comprises;

    i) a temperature coefficient of capacitance between plus 400 to minus 7112 parts per million per degree centigrade (ppm/°

    C);

    ii) a capacitance of between 10 and 20,000 picofarads;

    iii) wherein ESR is the sum of a dielectric loss plus an ohmic loss, and the capacitor comprises a dielectric loss tangent measured in ohms at an MRI RF pulsed frequency or range of frequencies that is less than five percent of the capacitor'"'"'s ESR; and

    iv) wherein the capacitor'"'"'s ESR at the MRI RF pulsed frequency or range of frequencies is less than 2.0 ohms; and

    h) wherein the conductive ferrule is configured to be disposed into an opening of the housing for an active implantable medical device.

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