| US 7,574,312 B2 | ||
| Semiconductor device and communications terminal and automobile having the same | ||
| Takeshi Nakayama, Nishinomiya (Japan); Eiji Takahashi, Kashiba (Japan); and Yoshiyuki Saito, Katano (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Filed on Nov. 08, 2005, as Appl. No. 11/268,662. | ||
| Claims priority of application No. 2004-323355 (JP), filed on Nov. 08, 2004. | ||
| Prior Publication US 2006/0097748 A1, May 11, 2006 | ||
| Int. Cl. G01F 23/00 (2006.01) | ||
| U.S. Cl. 702—75 [701/47] | 11 Claims |
| 1. A semiconductor device that is configured to operate at any of a plurality of predetermined frequencies, the semiconductor
device comprising:
a plurality of functional units;
a power source network having a plurality of branches that supply power from a power source to said pluraity of functional
units; and
a plurality of switching units, each of said switching units provided along one of said pluraltiy of branches for switching
ON/OFF the supply of power via the associate branch from the power source to said plurality of functional units, wherein
said plurality of functional units includes:
a storage unit configured to map and store the plurality of predetermined frequencies and pieces of switching information
designating on ON state or an OFF state of said switching units, the pieces of switching information being set to provide
different impedance values of said power source network; and
a control unit configured to read, from said storage unit, a piece of switching information corresponding to a current operating
frequency of the semiconductor device, and control the ON/OFF switching of said plurality of switching units in accordance
with the read piece of switching information,
the pieces of switching information are set so as to keep an impedance value of said power source network within a predetermined
range, for any of the plurality of predetermined frequencies at which the semiconductor device operates,
said plurality of functional units further includes a frequency detecting unit configured to monitor the current operating
frequency and, when the current operating frequency changes, detect a new current operating frequency after the change, and
said control unit read from said storage unit a piece of switching information corresponding to the current operating frequency
after change as detected by said frequency detecting unit.
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