ESD testing of giant magnetoresistive (GMR) heads with diodes is described. While the use of diodes did increase the magnetic and failure voltages of the GMR head, the magnetic failure voltage was increased much less than the resistance failure voltage. This results in an unfortunate side effect, which is to dramatically increase in the range over which magnetic damage occurs without a resistance change. This problem was especially clear for the case of two diodes in series. The current flow through the GMR head and diode were measured and agreed with SPICE circuit simulation results. The difference between magnetic and resistance protection is due to the nonlinear clamping behavior of the diode. It is concluded that serious magnetic damage will be the predominant failure signature for GMR heads with ESD protect diodes.
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