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US 8,138,768 B2Granted
Sensing circuit for devices with protective coating
AssigneeNXP B.V.
InventorsJohannes A. J. Van Geloven, Robertus A. M. Wolters, Nynke Verhaech
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AssigneeNXP B.V.
InventorsJohannes A. J. Van Geloven, Robertus A. M. Wolters, Nynke Verhaech
Estimating the term…
An integrated circuit has an inhomogeneous protective layer or coating over a circuit to be protected, and a sensing circuit (80) arranged to sense a first impedance of a part of the protective coating compared to a reference impedance (CO) located on the integrated circuit. The sensing circuit is able to measure a change in the first impedance, e.g. caused by tampering. The sensing circuit has an amplifier (OTA) having a feedback loop, such that the impedance being sensed is in the feedback loop. The sensing circuit can be incorporated in an oscillator circuit (OTA, Comp) so that the frequency depends on the impedance. Where the impedance is a capacitance, sensing electrodes adjacent to the protective layer or coating, form the capacitance. The electrodes can be arranged as selectable interdigitated comb structures, so that the protective layer or coating extends in between the teeth of the comb structures.
An integrated circuit having a circuit to be protected, a protective layer over the circuit to be protected, and a sensing circuit arranged to sense a first impedance of a first part of the protective layer compared to a reference impedance located on the integrated circuit, the sensing circuit also comprising an amplifier and a comparator, wherein an output of the amplifier is fed to an input of the comparator, and a main feedback path is fed from an output of the comparator back to an input of the amplifier, such that first and reference impedance being sensed are in the main feedback path.
An integrated circuit having a circuit to be protected, a protective layer over the circuit to be protected, and a sensing circuit arranged to sense a first impedance of a first part of the protective layer compared to a reference impedance located on the integrated circuit, the sensing circuit also comprising an amplifier and a comparator, wherein an output of the amplifier is fed to an input of the comparator, and a main feedback path is fed from an output of the comparator back to an input of the amplifier, such that first and reference impedance being sensed are in the main feedback path;
An integrated circuit having a circuit to be protected, a protective layer over the circuit to be protected, and a sensing circuit arranged to sense a first impedance of a first part of the protective layer compared to a reference impedance located on the integrated circuit, the sensing circuit also comprising an amplifier and a comparator, wherein an output of the amplifier is fed to an input of the comparator, and a main feedback path is fed from an output of the comparator back to an input of the amplifier, such that first and reference impedance being sensed are in the main feedback path;
A method of using an integrated circuit having a circuit to be protected, a protective layer being arranged over the circuit to be protected, the method comprising:
A method of manufacturing an integrated circuit, having the steps of forming a circuit to be protected, forming a protective layer over the circuit to be protected, and forming a sensing circuit to sense a first impedance of a first part of the protective layer and a reference impedance located on the integrated circuit, wherein the sensing circuit also comprises an amplifier and a comparator, wherein an output of the amplifier is fed to an input of the comparator, and a main feedback path is fed from an output of the comparator back to an input of the amplifier, such that first and reference impedance being sensed are in the main feedback path.
Dependencies are inferred from the claim text.