| US 7,463,177 B2 | ||
| Digital-to-analog converter with secondary resistor string | ||
| Shiming Lan, Tokyo (Japan); and Toshio Teraishi, Tokyo (Japan) | ||
| Assigned to Oki Semiconductor Co., Ltd., (Japan) | ||
| Filed on Jun. 18, 2007, as Appl. No. 11/812,293. | ||
| Application 11/293177 is a division of application No. 11/074692, filed on Mar. 09, 2005, granted, now 7,006,027. | ||
| Application 11/812293 is a continuation of application No. 11/293177, filed on Dec. 05, 2005, granted, now 7,250,889. | ||
| Claims priority of application No. 2004-202409 (JP), filed on Jul. 08, 2004. | ||
| Prior Publication US 2007/0247343 A1, Oct. 25, 2007 | ||
| Int. Cl. H03M 1/78 (2006.01) | ||
| U.S. Cl. 341—154 [341/144] | 6 Claims |
| 1. A method of designing a digital-to-analog (D/A) converter connected to a voltage generator using voltage drops in a resistor
string to generate a plurality of reference voltages forming a monotonic sequence of voltage levels, the D/A converter being
one of X D/A converters identically connected in parallel to the voltage generator to generate X analog voltages simultaneously,
X being a positive integer, the reference voltages having a variation tolerance of Y percent, Y being a positive number, the
resistors in the resistor string having equal resistance values RA, the method comprising:
designing a first control circuit for selecting a first arbitrary one of the plurality of reference voltages as a first output,
the first control circuit having a series resistance RB when conducting current from the voltage generator to the first output;
designing a second control circuit for selecting a second one of the plurality of reference voltages, adjacent in the monotonic
sequence to the first one of the plurality of reference voltages, as a second output; and
designing a third control circuit for generating a third output from the first output and the second output by turning one
or both of a first switching device and a second switching device on, the first switching device being connected in series
with a first resistor between the first output and the third output, the second switching device being connected in series
with a second resistor between the second output and the third output, the first resistor having a resistance RC such that
the combined series resistance of the first resistor and the first control circuit when conducting current is at least (50/Y)·X·RA.
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