Method and apparatus for protecting magnetoresistive heads from electrostatic discharge

An apparatus providing protection against current flow into a transducer during a first non-operating condition of the transducer, the transducer comprising a first and a second output terminal, the apparatus comprising:

• a first serial branch disposed between the first output terminal and ground, the first serial branch comprising a first fuse and a source/drain path of a first depletion mode transistor;
• a second serial branch disposed between the second output terminal and ground, the second serial branch comprising a second fuse and a source/drain path of a second depletion mode transistor;
• a first normally-open transistor having a first source/drain terminal connected between the first fuse and the first depletion mode transistor;
• a second normally-open transistor having a first source/drain terminal connected between the second fuse and the second depletion mode transistor;
• a control signal for placing the transducer in an operating condition, wherein the control signal closes the first and the second normally-open transistors permitting current flow from a power supply connected to a second source/drain terminal of the first and the second normally-open transistors through the first and the second depletion mode transistors and through the first and the second fuses to ground for opening the first and the second fuses;
• and
• wherein during the first non-operating condition the first and the second output terminals are shorted by the first and the second serial branches.

An apparatus comprising:

• a transducer having first and second differential output terminals;
• a first serial branch comprising a first fuse and a source/drain path of a first depletion mode transistor disposed between the first differential output terminal and a common node;
• a second serial branch comprising a second fuse and a source/drain path of a second depletion mode transistor disposed between the second differential output terminal and the common node;
• a first switching element having a first terminal connected between the first fuse and the first depletion mode transistor;
• a second switching element having a first terminal connected between the second fuse and the second depletion mode transistor;
• and
• the first and the second switching elements responsive to a control signal for causing current to flow through the first and the second switching elements for opening the first and the second fuses.

An apparatus for protecting a transducer from damage during an electrostatic discharge event, the transducer having first and second output terminals, the apparatus comprising:

• a first shorting branch connected between the first output terminal and a ground node;
• a second shorting branch connected between the second output terminal and a ground node;
• the first and the second shorting branches comprising a first and a second switch element, respectively, each controllable to an open state in response to a first control signal for opening the first and the second shorting branches;
• a third and a fourth switch element responsive to a power source and connected to the first and the second shorting branches respectively and each responsive to a second control signal for opening the first and the second shorting branches in response to current through the first and the second shorting branches as supplied by the power source.

A disk drive storage apparatus comprising:

• a transducer having a first and a second differential output terminal:
• a first fuse and a source/drain path of a first depletion mode transistor disposed between the first differential output terminal and a common node;
• a second serial branch comprising a second fuse and a source/drain path of a second depletion mode transistor disposed between the second differential output terminal and a common node;
• a first switching element having a first terminal connected to a common connection of the first fuse and the first depletion mode transistor;
• a second switching element having a first terminal connected to a common connection of the second fuse and the second depletion mode transistor;
• and
• a control signal for closing the first and the second switching elements to permit current flow through the first and the second fuses for opening the first and the second fuses.