Electronic apparatus

• US 7,224,349 B2
• Filed: 06/10/2003
• Issued: 05/29/2007
• Est. Priority Date: 06/18/2002
• Status: Expired due to Fees

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Irie, Michio
• Primary Examiner(s): Shalwala; Bipin
• Assistant Examiner(s): DHARIA, PRABODH M
• Application Number:
  US10/457,767
• Publication Number:
  US 20040041775A1
• Time in Patent Office: 1,449 Days
• Field of Search: 345/99, 345/204, 345/73.1, 345/558, 119/721, 340/10.1, 235/462.46, 455/296, 348/160, 607/60, 705/57, 375/130, 375/367, 375/219, 375/140, 375/142, 331/178, 331/78, 324/76.11, 382/232, 342/457, 342/127
• US Class Current: 345/204
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12
• CPC Class Codes: H04B 2001/7152 with means for suppressing interference

Abstract

The invention efficiently decreases EMI noise occurring with regard to the entirety of an electronic apparatus with a plurality of clocks as references for the operations. The spread spectrum is applied to the clock used by the largest number of ICs, that is, a display clock from among three types of clocks.

Claims

1. An electronic apparatus operating based on a plurality of types of clocks including a spread spectrum clock having a frequency spectrum that is spread and a non-spread spectrum clock having a frequency spectrum that is not spread, the electronic apparatus comprising:

a plurality of ICs using the clocks as references for operations, at least one clock that is used by a largest number of ICs being the spread spectrum clock from among the plurality of types of clocks,

wherein the plurality of ICs includes a first group of ICs and a second group of ICs, the spread spectrum clock being used by the first group of ICs, the non-spread spectrum clock being used by the second group of ICs, and the first group having a number of ICs that is larger than that of the second group.

6. The electronic apparatus as set forth in claim 1:

the at least one clock generator including at least a first clock generator generating the spread spectrum clock and a second clock generator generating the non-spread spectrum clock, the first clock generator and the second clock generator being constructed sharing the same IC.

8. The electronic apparatus as set forth in claim 1, another clock that is used by another IC being the non-spread spectrum clock, the another clock being different from the at least one clock that is used by the largest number of ICs, the another IC not being one of the largest number of ICs.

14. The electronic apparatus as set forth in claim 8, the another IC being an IC that belongs to an IC group having a second largest number of ICs or an IC that belongs to an IC group having a third largest number of ICs.

2. An electronic apparatus operating based on a plurality of types of clocks including a spread spectrum clock having a frequency spectrum that is spread and a non-spread spectrum clock having a frequency spectrum that is not spread, the electronic apparatus comprising:

a plurality of ICs using the clocks as references for operations; and

at least one clock generator generating the clocks, at least one clock with a longest signal path from the clock generator generating the clock to the IC where the clock is ultimately provided being the spread spectrum clock from among the plurality of types of clocks,

wherein the plurality of ICs includes a first IC and a second IC, the spread spectrum clock being used by the first IC, the non-spread spectrum clock being used by the second IC, and a signal path from the at least one clock generator to the first IC being longer than that from the at least one clock generator to the second IC.

9. The electronic apparatus as set forth in claim 2, another clock being the non-spread spectrum clock, the other clock being different from the at least one clock.

3. An electronic apparatus, comprising:

a structure being operable based on a plurality of types of clocks including a spread spectrum clock having a frequency spectrum that is spread and a non-spread spectrum clock having a frequency spectrum that is not spread, at least one clock with a highest frequency being the spread spectrum clock from among the plurality of types of clocks,

wherein the plurality of clocks includes a first clock and a second clock, the spread spectrum clock being the first clock, the non-spread spectrum clock being the second clock, and the first clock having a frequency higher than that of the second clock.

10. The electronic apparatus as set forth in claim 3, another clock being the non-spread spectrum clock, the other clock being different from the at least one clock with the highest frequency.

4. An electronic apparatus operating based on a plurality of types of clocks including a spread spectrum clock having a frequency spectrum that is spread and a non-spread spectrum clock having a frequency spectrum that is not spread, the electronic apparatus comprising:

at least one clock generator generating the clocks, at least one clock with a highest output current from the clock generator being the spread spectrum clock from among the plurality of types of clocks,

wherein the plurality of clocks include a first clock and a second clock, the spread spectrum clock being the first clock, the non-spread spectrum clock being the second clock, and the first clock having an output current from the clock generator that is higher than the current from the clock generator to the second clock.

11. The electronic apparatus as set forth in claim 4, another clock being the non-spread spectrum clock, the other clock being different from the at least one clock with the highest output current.

5. An electronic apparatus operating based on a plurality of types of clocks including a spread spectrum clock having a frequency spectrum that is spread and a non-spread spectrum clock having a frequency spectrum that is not spread, the electronic apparatus comprising:

at least one clock generator generating the clocks, at least one clock with a highest driving power voltage of driving the clock generator being the spread spectrum clock from among the plurality of types of clocks,

wherein the plurality of clocks include a first clock and a second clock, the spread spectrum clock being the first clock, the non-spread spectrum clock being the second clock, and the first clock having a driving power voltage higher than that of the second clock.

12. The electronic apparatus as set forth in claim 5, another clock being the non-spread spectrum clock, the other clock being different from the at least one clock with the highest driving power voltage.

7. A projector, comprising:

a liquid crystal panel operable based on a plurality of types of clocks including a spread spectrum clock having a frequency spectrum that is spread and a non-spread spectrum clock having a frequency spectrum that is not spread, at least one clock ultimately provided to the liquid crystal panel being the spread spectrum clock from among the plurality of types of clocks, and

a plurality of ICs using the clocks as references for operations, at least one clock that is used by a largest number of ICs being the spread spectrum clock from among the plurality of types of clocks,

wherein the plurality of ICs includes a first group of ICs and a second group of ICs, the spread spectrum clock being used by the first group of ICs, the non-spread spectrum clock being used by the second group of ICs, and the first group having a number of ICs that is larger than that of the second group.

13. The projector as set forth in claim 7, another clock being the non-spread spectrum clock, the other clock being different from the at least one clock ultimately provided to the liquid crystal panel.