Variable impedance sense architecture and method
First Claim
Patent Images
1. A variable impedance sense circuit, comprising:
- a comparator having inputs coupled to at least a first array of switchable impedance elements, the comparator outputting a first drift value that indicates a detected change in the impedance of the first array; and
at least a first counter circuit that generates a count value for calibrating the first array, the at least first counter circuit modifying the count value in response to the first drift value when such a modification does not increase an impedance difference between the first array and a reference impedance to generate an output count value.
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Abstract
A variable impedance sense (VIS) circuit (400) can detect a drift in the impedance of variable impedance circuits due to changes in operating conditions. Adjustments to binary impedance setting codes are made in response to a detected drift only when such changes do not increase a worst case variation from a target impedance. Adjustments can also be made in response to a detected input offset polarity.
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Citations
21 Claims
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1. A variable impedance sense circuit, comprising:
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a comparator having inputs coupled to at least a first array of switchable impedance elements, the comparator outputting a first drift value that indicates a detected change in the impedance of the first array; and at least a first counter circuit that generates a count value for calibrating the first array, the at least first counter circuit modifying the count value in response to the first drift value when such a modification does not increase an impedance difference between the first array and a reference impedance to generate an output count value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of sensing an impedance value for input/output (I/O) matching that compensates for drifts in variable impedance elements, comprising the steps of:
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detecting a first drift change in variable impedance elements; generating a multi-bit digital value corresponding to a reference impedance with an analog-to-digital conversion; and adjusting the digital value according to the first drift change in the variable impedance elements when such an adjustment does not increase an impedance difference between the variable impedance elements and the reference impedance. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A variable impedance sensing architecture, comprising:
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an analog-to-digital converter (ADC) circuit having inputs coupled to a first variable impedance array and a second variable impedance array that outputs a drift indication reflecting a change in at least one of the variable impedance arrays and an input offset indication; and a counter/control circuit that selectively adjusts a binary code representing an impedance of at least one of the variable impedance arrays in response to at least the drift indication value and the input offset indication. - View Dependent Claims (18, 19, 20, 21)
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Specification