Output buffer circuit with control circuit for modifying supply voltage and transistor size
First Claim
1. A data processing system comprising:
- a first semiconductor integrated circuit;
a second semiconductor integrated circuit;
a transmission line that connects a first external output buffer of the first semiconductor integrated circuit to the second semiconductor integrated circuit, and connects a second external output buffer of the second semiconductor integrated circuit to the first semiconductor integrated circuit; and
an external power supply circuit that generates an operational supply voltage to the first and the second external output buffers,wherein the first semiconductor integrated circuit instructs the external power supply circuit to be able to modify a level of the operational supply voltage, and includes a first operation mode capable of selectively controlling an output transistor size of the first external output buffer according to the operational supply voltage supplied according to the instruction, and wherein the second semiconductor integrated circuit includes a second operation mode capable of selectively controlling the output transistor size of the second external output buffer according to the operational supply voltage supplied from the external power supply circuit.
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Accused Products
Abstract
In this invention, a control circuit (111) controls both the power supply voltage (VDDQ) and the transistor size of the external output buffer to thereby select the lowest supply voltage that achieves the impedance matching with the transmission line (100), to thereby save bus termination by a resistor, thus consequently achieving both the lowering of the power consumption and the speeding-up in the data transmission. The power consumption during the data transmission is proportional to the square of the supply voltage. If the operational supply voltage of the external output buffer is lowered, the power consumption will be reduced accordingly. If the operational supply voltage of the external output buffer is lowered, the impedance thereof will be increased apparently; and at the same time, if the transistor size of the external output buffer is increased, the increased impedance will be decreased. By bringing the output impedance (ON-resistance) of the external output buffer into conformity with the impedance of the transmission line, it becomes possible to output the signal without distortions on the waveform.
13 Citations
15 Claims
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1. A data processing system comprising:
- a first semiconductor integrated circuit;
a second semiconductor integrated circuit;
a transmission line that connects a first external output buffer of the first semiconductor integrated circuit to the second semiconductor integrated circuit, and connects a second external output buffer of the second semiconductor integrated circuit to the first semiconductor integrated circuit; and
an external power supply circuit that generates an operational supply voltage to the first and the second external output buffers,wherein the first semiconductor integrated circuit instructs the external power supply circuit to be able to modify a level of the operational supply voltage, and includes a first operation mode capable of selectively controlling an output transistor size of the first external output buffer according to the operational supply voltage supplied according to the instruction, and wherein the second semiconductor integrated circuit includes a second operation mode capable of selectively controlling the output transistor size of the second external output buffer according to the operational supply voltage supplied from the external power supply circuit. - View Dependent Claims (2, 3, 4, 5, 6)
- a first semiconductor integrated circuit;
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7. A data processing system comprising:
- a first semiconductor integrated circuit;
a second semiconductor integrated circuit; and
a transmission line that connects a first external output buffer of the first semiconductor integrated circuit to the second semiconductor integrated circuit, and connects a second external output buffer of the second semiconductor integrated circuit to the first semiconductor integrated circuit,wherein the first semiconductor integrated circuit includes an internal power supply circuit that generates an operational supply voltage to the first and the second external output buffers, instructs the internal power supply circuit to be able to modify a level of the operational supply voltage, and includes a first operation mode capable of selectively controlling an output transistor size of the first external output buffer according to the operational supply voltage generated according to the instruction, and wherein the second semiconductor integrated circuit includes a second operation mode capable of selectively controlling the output transistor size of the second external output buffer according to the operational supply voltage supplied from the internal power supply circuit of the first semiconductor integrated circuit. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
- a first semiconductor integrated circuit;
Specification