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US 6,686,859 B2Granted
Digital-to-analog-converter
AssigneeMotorola, Inc.
InventorsMasami Aiura, Satoshi Takahashi, Yuichi Nakatani
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AssigneeMotorola, Inc.
InventorsMasami Aiura, Satoshi Takahashi, Yuichi Nakatani
Estimating the term…
It is an objective to provide a digital-to-analog converter circuit that allows the value of the current output from each current source cell to be identical, regardless of the position of that current source cell relative to the power supply line. To ensure that the voltages supplied to the respective current source cells are identical, the power supply lines La and Lb are disposed in the form of a right triangle modified such that their line widths W1 and W2 become constantly narrower on one side depending on the position at which the power supply lines La and Lb are formed. The power supply lines La and Lb are also disposed such that their hypotenuses are opposite to each other.
A digital-to-analog converter circuit, wherein a plurality of current source cells having a first constant current source and a second constant current source are arranged in one direction;
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
By averaging out the errors, e.g. using sliding scale: in the spatial domain
The original and additional components or elements being complementary to each other, e.g. CMOS: using a differential network structure, i.e.…
Using current sources as quantisation value generators: with equal currents which are switched by unary decoded digital signals
Coding
Term ended 27 Jan 2023 (estimated)
The present invention relates to digital-to-analog converter circuits.
Conventionally, as one of digital-to-analog converter circuits, there is a current output type digital-to-analog converter that is ideally suited for image signal processing. FIG. 11 is a circuit diagram depicting one example of a current output type digital-to-analog converter circuit formed on a semiconductor chip, where its input digital data is 4 bits.
In FIG. 11, the current output type digital-to-analog converter circuit 50 has sixteen current source cells 51a-51p disposed at regular intervals. Each of the current source cells 51a-51p comprises first and second constant current sources G1 and G2, respectively, that share an output terminal 52 thereof.
FIG. 1 is a circuit diagram of a current output type digital-to-analog converter circuit according to an embodiment of the present invention.
FIG. 2 is a plan view of first and second power supply lines of the same current output type digital-to-analog converter circuit.
FIG. 3 is a chart depicting the amount of voltage drop at each position of the power supply line due to the respective line resistance in the same current output type digital-to-analog converter circuit.
One embodiment of the digital-to-analog converter circuit that embodies the present invention is described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram depicting one example of a current output type digital-to-analog converter circuit formed on a semiconductor chip, where its input digital data is 4 bits.
In FIG. 1, the current output type digital-to-analog converter circuit 10 has sixteen current source cells 11a-11p arranged at regular intervals. Each of the current source cells 11a-11p is comprised of first and second constant current sources Ga and Gb, respectively, that share an output terminal 12 thereof.
Each of the output terminals 12 is electrically connected to first and second analog output lines 14a and 14b via a changeover switch S, respectively. Each of the changeover switches S is electrically connected to a decoder circuit, which is not shown. Each changeover switch S is designed so that the output terminal 12 is electrically connected to either of a first analog output line 14a or a second analog output line 14b in accordance with a control signal from the decoder circuit.