Tolerant input circuit
First Claim
1. A tolerant input circuit for connection to a power supply and an input pad, the tolerant input circuit comprising:
- an input circuit;
a step-down device including a first N-channel MOS transistor connected between the input pad and the input circuit, the first N-channel MOS transistor of the step-down device having a gate supplied with voltage from the power supply, wherein voltage of a high voltage signal provided to the input pad is decreased to a value lower than or equal to that of the voltage of the power supply by the step-down device and provided to the input circuit, the first N-channel MOS transistor including a back gate; and
a back gate voltage control circuit, connected to the back gate of the first N-channel MOS transistor in the step-down device, for increasing back gate voltage of the first N-channel MOS transistor in the step-down device when the input pad is provided with the high voltage signal.
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Accused Products
Abstract
A tolerant input circuit that functions stably regardless of fabrication differences without having to adjust the threshold value of an input circuit. The tolerant input circuit includes a step-down device configured by an N-channel MOS transistor connected between an input pad and the input circuit. Voltage from a power supply is supplied to the gate of the N-channel MOS transistor in the step-down device to decrease the voltage of a high voltage signal provided to the input pad to the voltage of the power supply or lower. The signal with decreased voltage is provided to the input circuit. The tolerant input circuit includes a back gate voltage control circuit for increasing back gate voltage of the N-channel MOS transistor in the step-down device when the input pad is provided with a high voltage signal.
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Citations
15 Claims
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1. A tolerant input circuit for connection to a power supply and an input pad, the tolerant input circuit comprising:
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an input circuit;
a step-down device including a first N-channel MOS transistor connected between the input pad and the input circuit, the first N-channel MOS transistor of the step-down device having a gate supplied with voltage from the power supply, wherein voltage of a high voltage signal provided to the input pad is decreased to a value lower than or equal to that of the voltage of the power supply by the step-down device and provided to the input circuit, the first N-channel MOS transistor including a back gate; and
a back gate voltage control circuit, connected to the back gate of the first N-channel MOS transistor in the step-down device, for increasing back gate voltage of the first N-channel MOS transistor in the step-down device when the input pad is provided with the high voltage signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A tolerant input circuit for connection to a power supply and an input pad, the tolerant input circuit comprising:
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an input circuit;
a first N-channel MOS transistor connected between the input pad and the input circuit, the first N-channel MOS transistor having a gate connected to the power supply, the first N-channel MOS transistor including a back gate; and
a second N-channel MOS transistor connected between the input pad and the back gate of the first N-channel MOS transistor. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A tolerant input circuit for connection to a power supply and an input pad, the tolerant input circuit comprising:
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an input circuit;
a first N-channel MOS transistor connected between the input pad and the input circuit, the first N-channel MOS transistor having a gate connected to the power supply and a back gate connected to a node between the first N-channel MOS transistor and the input circuit. - View Dependent Claims (15)
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Specification