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Signal transmitting device, circuit block and integrated circuit suited to fast signal transmission
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Inventors: Takekuma, Toshitsugu; Kurihara, Ryoichi; Yamagiwa, Akira;
Assignee: Hitachi, Ltd. (Tokyo, JP)
Primary Examiner: Tokar; Michael
Assistant Examiner: Roseen; Richard
Attorney, Agent or Firm: Antonelli, Terry, Stout & Kraus, LLP
A signal transmitting circuit includes one or more circuit blocks having a driving circuit and an intra-block transmission line for transmitting a signal produced by the driving circuit, one or more circuit blocks having a receiving circuit and an intra-block transmission line for transmitting the signal to said receiving circuit, and a main interblock transmission line for propagating a signal between both of the driving and receiving circuit blocks. Inter-block transmission line is terminated at one or two ends by one or two resistors having substantially the same impedance as the interblock transmission line itself. Each of the intra-block transmission line is provided with a resistance element having a resistance equal to or close to a value derived by subtracting a half of an impedance of the inter-block transmission line from an impedance of the intra-block transmission line, to lower signal amplitude and suppress reflections of a signal at branch points along the main interblock transmission line, thereby enabling a high-speed signal transfer. |
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DETAILED DESCRIPTION It is an object of the present invention to provide a signal transmitting device, a circuit block, and an integrated circuit which are arranged to overcome the foregoing disadvantages, suppress the drop of a signal potential on a transmission line having branched lines, prevent repetitive reflections in each branched line, and keep an amplitude of a signal small on the line, for quickly transmitting a signal.
To achieve the object in a preferred mode, a signal transmitting device comprises a first circuit block including a driving circuit for driving a signal and an intra-block transmission line for transmitting a signal from the driving circuit to the outside of the circuit block, a second circuit block including a receiving circuit for receiving a signal and an intra-block transmission line for transmitting a signal to be inputted to the receiving circuit, and an inter-block transmission line for transmitting the signal between the circuit blocks, wherein the inter-block transmission line is terminated by one or two elements each having a resistance equal to or close to a characteristic impedance value of the inter-block transmission line.
In addition, the resistance of each of resistors 80 to 83 is provided with a resistance equal to or close to a value obtained by subtracting a half of the impedance of the inter-block transmission line from the impedance of the intra-block transmission line.
In a circuit device having plural blocks each having both of a driving circuit and a receiving circuit, likewise, the inter-block transmission line is terminated by one or two elements each having a resistance equal to or close to a characteristic impedance of the inter-block transmission line.
Each intra-block transmission line is provided to have a resistance equal to or close to a value obtained by subtracting a half of the characteristic impedance of the inter-block transmission line from the impedance of the intra-block transmission line.
In the case where a package with a long lead frame such as quad flat package (QFP) or a pin grid array (PGA) is used in an integrated circuit having a driving or a receiving circuit integrated thereon termination is made to the inter-block transmission line, a resistor is provided for impedance matching between the inter-block transmission line and the intra-block transmission line, and the impedance of the lead frame and the impedance of the intra-block transmission line are matched
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