Methods and apparatus for trimming electrical devices
AssigneeTexas Instruments Incorporated
InventorsGregory G. Romas, Jr., Jian Wang
Life of this patent
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Abstract
Trimming methods and apparatus are disclosed for selectively removing resistance between first and second nodes in an electrical device, including trim circuits comprising a resistor and a diode formed in the resistor body having a conductive portion which may be selectively melted to short the resistor. A multi-bit trim cell is disclosed having trim cells individually comprising a resistor with a diode formed in the resistor body for selectively shorting the resistor, and a fuse for selectively disconnecting the diode from a trim pad.
Claims29
A trim circuit for providing a selectively removable resistance between first and second nodes in an electrical device, comprising:
- a resistor comprising a resistor body and first and second ends and providing an electrical resistance between the first and second nodes, the first end of the resistor being connected to the first node and to a first pad in the electrical device;
- and
- a diode formed in the resistor body and comprising an anode, a cathode, and a conductive portion connected to one of the anode and the cathode, the anode being connected to the second end of the resistor, and the cathode being connected to a second pad in the electrical device;
- wherein the conductive portion of the diode connects the first and second ends of the resistor so as to remove resistance between the first and second nodes after a trim voltage is applied across the first and second pads.
A multi-bit trim circuit for providing a selectively removable resistance between first and second nodes in an electrical device, comprising:
- a first trim cell connected to the first node and to first and second pads in the electrical device;
- and
- a second trim cell connected between the first trim cell and the second node;
- wherein the first and second trim cells individually comprise:
- a resistor comprising a resistor body extending in a substrate between first and second ends and providing an electrical resistance between the first and second nodes;
- and
- a diode formed in the resistor body and comprising an anode, a cathode, and a conductive portion connected to the cathode, the anode being connected to the second end of the resistor, the cathode being connected to the second pad, and the conductive portion connecting the first and second ends of the resistor.
A trim circuit for providing a selectively removable resistance between first and second nodes in an electrical device, comprising:
- a resistor comprising a resistor body and first and second ends and providing an electrical resistance between the first and second nodes, the first end of the resistor being connected to the first node and to a first pad, and the second end of the resistor being connected to the second node;
- a diode, formed in said resistor body and comprising an anode connected to the second end of the resistor, a cathode, and a conductive portion connected to the cathode to electrically connect the first and second ends of the resistor after a trim voltage is applied across the first and second pads;
- and
- a fuse connected between the conductive portion of the diode and a second pad to selectively disconnect the cathode from the second pad after a trim current is applied between the first and second pads.
A method of trimming an electrical device to selectively remove resistance between two nodes in the device, the method comprising:
- applying a trim voltage across first and second pads in the electrical device to short a first resistor in a first trim cell between the two nodes,
- applying a trim current between the first and second pads to disconnect the first trim cell from the second pad;
- determining if further trimming is needed;
- and
- repeating application of the trim voltage and the trim current to remove further resistance the two nodes if further trimming is needed.
The method of clam 24, wherein applying the trim voltage comprises applying about 8 volts at about 600 mA across the first and second pads to short the first resistor.
Dependencies are inferred from the claim text.