Microcomputer having a built-in A/D converter with a resistor between an external terminal and an I/O circuit
First Claim
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1. A microcomputer comprising:
- an internal circuit having a data processing function;
a built-in A/D converter circuit connected to said internal circuit;
an I/O circuit connected to said internal circuit;
an external terminal for input/output shared by an input terminal of said A/D converter circuit;
a first branch wire connecting said external terminal via said I/O circuit to said internal circuit;
a second branch wire connecting said external terminal to said A/D converter circuit, and a predetermined resistor inserted on said first branch wire connecting said external terminal to said I/O circuit and designed to have a sufficiently higher resistance than a parasitic resistance of said first branch wire.
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Abstract
The present invention provides a microcomputer having a built-in A/D converter circuit and sharing an external terminal with an input terminal of the A/D converter so as to reduce the size and weight of the semiconductor integrated circuit, wherein a resistor is inserted to eliminate deterioration of the A/D converter circuit due to the reduction in the number of the terminals.
16 Citations
6 Claims
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1. A microcomputer comprising:
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an internal circuit having a data processing function;
a built-in A/D converter circuit connected to said internal circuit;
an I/O circuit connected to said internal circuit;
an external terminal for input/output shared by an input terminal of said A/D converter circuit;
a first branch wire connecting said external terminal via said I/O circuit to said internal circuit;
a second branch wire connecting said external terminal to said A/D converter circuit, and a predetermined resistor inserted on said first branch wire connecting said external terminal to said I/O circuit and designed to have a sufficiently higher resistance than a parasitic resistance of said first branch wire. - View Dependent Claims (2, 3, 4, 5, 6)
a first-conductive field effect transistor (FET) having a source connected to a high-potential power source, a gate supplied with a first control signal from said internal circuit, and a drain connected to a terminal of said predetermined resistor;
a second-conductive field effect transistor (FET) having a drain connected to said drain of said first-conductive FET, a gate supplied with a second control signal from said internal circuit, and a source connected to a low-potential power source; and
a NAND circuit having a first input terminal connected to said terminal of said predetermined resistor, a second input terminal supplied with an input control signal from said internal circuit, and an output terminal connected to said internal circuit.
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4. A microcomputer as claimed in claim 2, wherein said I/O circuit includes:
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a first-conductive field effect transistor (FET) having a source connected to a high-potential power source, a gate supplied with a first control signal from said internal circuit, and a drain connected to a terminal of said predetermined resistor;
a second-conductive field effect transistor (FET) having a drain connected to said drain of said first-conductive FET, a gate supplied with a second control signal from said internal circuit, and a source connected to a low-potential power source; and
a NAND circuit having a first input terminal connected to said terminal of said predetermined resistor, a second input terminal supplied with an input control signal from said internal circuit, and an output terminal connected to said internal circuit.
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5. The microcomputer according to claim 1, wherein the predetermined resistor is designed to have a resistance value at least one hundred times the parasitic resistance of the first branch wire.
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6. The microcomputer according to claim 2, wherein the predetermined resistor is designed to have a resistance value at least one hundred times the parasitic resistance of the first branch wire.
Specification